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Re: Vanguard V-Twin allowable thrust loads

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  • Maldague
    Taking advantage of the ball bearing seem to be just logic. But that bearing is installed on the PTO side and there has also been comments on having mass of
    Message 1 of 13 , Jan 2, 2013
      Taking advantage of the ball bearing seem to be just logic.
      But that bearing is installed on the PTO side and there has also been comments on having mass of inertia installed at both ends of the crankshaft that would increase stress compare to having both the flywheel and the prop installed at the same side. Not sure if that is valid?

      Jmm


      --- In Small4-strokeEngines@yahoogroups.com, "Kev A" <kevin@...> wrote:
      >
      > Fetched up this old post as it contains useful info
      >
      > Seems like the PTO side is best to stand propeller pull, especially as the crank shoulder will be up against the double roll ball bearing.
      >
      > I've used a Challenge taper lock parallel sided bush to lock my pulley on the shaft, in the bigger sizes it will stand prop inertia loads
      >
      > Kev
      >
      >
      > --- In Small4-strokeEngines@yahoogroups.com, "William Rich" <williamrich1@> wrote:
      > >
      > >
      > > Let's look at the good news - both B+S sources and the B+S Vanguard
      > > Application Book say the PTO can withstand at least a 250 lbs of outward
      > > thrust (some say 500 lbs). Why not turn the motor around and mount the
      > > tractor propeller on the PTO? I've always wondered how secure a mounting
      > > the flywheel is anyway. I've believe the Volkswagen people mount the
      > > hub on a shaft - maybe we can use one of their techniques?
      > >
      > >
      > > --- In Small4-strokeEngines@yahoogroups.com, "William Rich"
      > > <williamrich1@> wrote:
      > > >
      > > >
      > > > What we need is more documentation. The only thing we have is the B+S
      > > > application book in the Files folder. It supports the 50lb flywheel
      > > > outward limit. I suspect not all Vanguard V-Twin models have the same
      > > > crankshaft constraints. We also might be getting conflicting official
      > > > versions and accurate insider know-how versions. Either way - due
      > > > dilignece requires DOCUMENTATON.
      > > >
      > > >
      > > > --- In Small4-strokeEngines@yahoogroups.com, "William Rich"
      > > > williamrich1@ wrote:
      > > > >
      > > > >
      > > > > Mr. Tinka, the Czech Republic pilot with the Vanguard powered SD-1,
      > > > > shared with us earlier how Czech Republic B+S technical support
      > > seemed
      > > > > to indicate you can safely apply up to 250 lbs of outward thrust to
      > > > the
      > > > > flywheel end of the crankshaft. This was wonderful news! However, Al
      > > > at
      > > > > V-Twin Performance (site with motor sounds) finally responded to my
      > > > > email with information from an American B+S engineer that is
      > > > > contradictory. The engineer seems to says you CANNOT pull on
      > > flywheel
      > > > > side of crankshaft with force greater than 50 lbs!
      > > > >
      > > > > Here is my email exchange with Al and the B+S engineer:
      > > > >
      > > > > ---------------------------------
      > > > > ----- Original Message ----- From: WilliamRich
      > > > >
      > > >
      > > <mhtml:{3A2E637E-294D-4D22-AB7E-98231855CB44}mid://00000099/!x-usc:mailt\
      > > \
      > > > \
      > > > > o:williamrich1@ To: vtwins@
      > > > >
      > > >
      > > <mhtml:{3A2E637E-294D-4D22-AB7E-98231855CB44}mid://00000099/!x-usc:mailt\
      > > \
      > > > \
      > > > > o:vtwins@ Sent: Monday, July 13, 2009 8:47 AM
      > > > > Subject: Re: Air boat and similar V Twin propeller applications
      > > > > Al, The ball bearing is on the PTO side and the sleeve bearing is on
      > > > > the flywheel side (I'm sure you know this). Czech Republic B+S tech
      > > > > support says you can pull outward on either end of the crankshaft up
      > > > to
      > > > > 250 lbs. The say you cannot push inward on either end of the
      > > > crankshaft
      > > > > with more than 50 lbs because the column of the crankshaft will
      > > bend.
      > > > > Your B+S engineering contact seems to say the net PTO outward thrust
      > > > > must not exceed 500 lbs, and the net flywheel outward thrust must
      > > not
      > > > > exceed 50 lbs because the ball bearing handles thrust much better
      > > than
      > > > > the sleeve bearing. This could be a problem if your contact is
      > > correct
      > > > > because there are craft with tractor propellers pulling outward on
      > > the
      > > > > flywheel end of the crankshaft with a thrust of 150 lbs. William
      > > Rich
      > > > > ----- Original Message ----- From: vtwins@
      > > > >
      > > >
      > > <mhtml:{3A2E637E-294D-4D22-AB7E-98231855CB44}mid://00000099/!x-usc:mailt\
      > > \
      > > > \
      > > > > o:vtwins@ To: WilliamRich
      > > > >
      > > >
      > > <mhtml:{3A2E637E-294D-4D22-AB7E-98231855CB44}mid://00000099/!x-usc:mailt\
      > > \
      > > > \
      > > > > o:williamrich1@ Sent: Monday, July 13, 2009 8:33 AM Subject:
      > > > > Re: Air boat and similar V Twin propeller applications
      > > > > William, I hope this reply will help you answer some of your
      > > > > questions. Al I was out on vacation and just catching up. The
      > > > > axial bearing load capability is based on the type of surface that
      > > the
      > > > > thrust is applied to. The ball bearing on the PTO side can handle
      > > 500
      > > > > pounds of thrust and the sleeve bearing on the flywheel end can
      > > handle
      > > > > 50 pounds of thrust. If you have axial loads on both sides of the
      > > > > engine, the net load is used to determine acceptance. For example,
      > > if
      > > > > you have 500 pounds axial load pulling on the PTO side and 500
      > > pounds
      > > > > pushing on the flywheel side, the net is 1000 pounds on the PTO side
      > > > > which is excessive. If you have equivalent loads pulling on both
      > > sides
      > > > > of the engine, the net will be 0 and is acceptable. ----- Original
      > > > > Message ----- From: WilliamRich
      > > > >
      > > >
      > > <mhtml:{3A2E637E-294D-4D22-AB7E-98231855CB44}mid://00000099/!x-usc:mailt\
      > > \
      > > > \
      > > > > o:williamrich1@ To: vtwins@
      > > > >
      > > >
      > > <mhtml:{3A2E637E-294D-4D22-AB7E-98231855CB44}mid://00000099/!x-usc:mailt\
      > > \
      > > > \
      > > > > o:vtwins@ Sent: Monday, July 06, 2009 4:32 PM
      > > > > Subject: Re: Air boat and similar V Twin propeller applications
      > > > > Thank you very much Al. ----- Original Message ----- From:
      > > > > vtwins@
      > > > >
      > > >
      > > <mhtml:{3A2E637E-294D-4D22-AB7E-98231855CB44}mid://00000099/!x-usc:mailt\
      > > \
      > > > \
      > > > > o:vtwins@ To: WilliamRich
      > > > >
      > > >
      > > <mhtml:{3A2E637E-294D-4D22-AB7E-98231855CB44}mid://00000099/!x-usc:mailt\
      > > \
      > > > \
      > > > > o:williamrich1@ Sent: Monday, July 06, 2009 1:25 PM Subject:
      > > > > Re: Air boat and similar V Twin propeller applications
      > > > > William, I have forwarded your info request to a friend of mine who
      > > > > is an application engineer at Briggs. He is on vacation till the
      > > 13th
      > > > of
      > > > > July. I'll forward any helpfull info that he offers. Thanks,
      > > > > Al ----- Original Message ----- From: WilliamRich
      > > > >
      > > >
      > > <mhtml:{3A2E637E-294D-4D22-AB7E-98231855CB44}mid://00000099/!x-usc:mailt\
      > > \
      > > > \
      > > > > o:williamrich1@ To: vtwins@
      > > > >
      > > >
      > > <mhtml:{3A2E637E-294D-4D22-AB7E-98231855CB44}mid://00000099/!x-usc:mailt\
      > > \
      > > > \
      > > > > o:vtwins@ Sent: Monday, July 06, 2009 3:30 PM
      > > > > Subject: Air boat and similar V Twin propeller applications
      > > > > Sirs, I know you run a business and your time is precious - what we
      > > > > are interested in is your performance products (of course!), and any
      > > > > strengthening of the drive train that you might deem appropriate to
      > > > > handle direct-drive propeller loads. The Vanguard V-Twin
      > > Applications
      > > > > Manual has a crankshaft load table that defines the axial load limit
      > > > as
      > > > > 50 lbs inward and 500 lbs outward. I don't know if the outward limit
      > > > of
      > > > > 500 lbs applies to pulling on both ends of the crankshaft, and the
      > > 50
      > > > lb
      > > > > inward limit applies to pushing on both ends of the crankshaft; or
      > > if
      > > > > the limits apply to the PTO only. I have deduced that if the limits
      > > > > apply to both ends, then the 50 lb limit is to prevent the
      > > crankshaft
      > > > > column from bending under compression. Otherwise, the different
      > > axial
      > > > > load limits - 50 lbs and 500 lbs - suggest that one bearing type,
      > > > sleeve
      > > > > or ball-bearing, withstands axial loads much better than the other.
      > > > > All things considered, I suspect that pulling on the PTO with up to
      > > > 500
      > > > > lbs force is ok because the ball-bearing can take the axial rotary
      > > > > compression, while pulling on the flywheel end is limited to 50 lbs
      > > > > because the sleeve bearing does not take axial rotary compression
      > > > well.
      > > > > This is important because some builders are placing the propeller
      > > hub
      > > > on
      > > > > the flywheel in tractor configuration (pulling). This is not good if
      > > > > they are applying 150 lbs of force against a 50 lb limit - it will
      > > > work
      > > > > for a while then trouble. In any event, any light you can shed on
      > > how
      > > > > to best attach a direct-drive propeller to a V-Twin crankshaft would
      > > > be
      > > > > very much appreciated. We also are very interested in dual-plug
      > > > > heads. You excellent reputation is well known and we look forward to
      > > > > doing business with you. Best regards, William Rich
      > > > > ---------------------------------
      > > > >
      > > > >
      > > > >
      > > > > [Non-text portions of this message have been removed]
      > > > >
      > > >
      > >
      >
    • Kev A
      You re right, acceleration would be different if the inertia was too different, with one end lagging and flexing the crank. With a flywheel on one end only,
      Message 2 of 13 , Jan 2, 2013
        You're right, acceleration would be different if the inertia was too different, with one end lagging and flexing the crank. With a flywheel on one end only, the other end can de stress itself and no nasty harmonics.

        Answer is to fit a Luciole type alloy spider in place of the flywheel, carrying the ring gear and one magnet and counterweight. Hardly any inertia and lots of heavy iron neatly disposed of.

        Generator could go on either side.

        I'd best shut up and go fix something; got a new trike coming from India to bolt my engine into, it is ten pounds lighter with the latest design changes.

        Cheers

        Kev

        --- In Small4-strokeEngines@yahoogroups.com, "Maldague" <jmmaldague@...> wrote:
        >
        > Taking advantage of the ball bearing seem to be just logic.
        > But that bearing is installed on the PTO side and there has also been comments on having mass of inertia installed at both ends of the crankshaft that would increase stress compare to having both the flywheel and the prop installed at the same side. Not sure if that is valid?
        >
        > Jmm
        >
        >
        > --- In Small4-strokeEngines@yahoogroups.com, "Kev A" <kevin@> wrote:
        > >
        > > Fetched up this old post as it contains useful info
        > >
        > > Seems like the PTO side is best to stand propeller pull, especially as the crank shoulder will be up against the double roll ball bearing.
        > >
        > > I've used a Challenge taper lock parallel sided bush to lock my pulley on the shaft, in the bigger sizes it will stand prop inertia loads
        > >
        > > Kev
        > >
        > >
        > > --- In Small4-strokeEngines@yahoogroups.com, "William Rich" <williamrich1@> wrote:
        > > >
        > > >
        > > > Let's look at the good news - both B+S sources and the B+S Vanguard
        > > > Application Book say the PTO can withstand at least a 250 lbs of outward
        > > > thrust (some say 500 lbs). Why not turn the motor around and mount the
        > > > tractor propeller on the PTO? I've always wondered how secure a mounting
        > > > the flywheel is anyway. I've believe the Volkswagen people mount the
        > > > hub on a shaft - maybe we can use one of their techniques?
        > > >
        > > >
        > > > --- In Small4-strokeEngines@yahoogroups.com, "William Rich"
        > > > <williamrich1@> wrote:
        > > > >
        > > > >
        > > > > What we need is more documentation. The only thing we have is the B+S
        > > > > application book in the Files folder. It supports the 50lb flywheel
        > > > > outward limit. I suspect not all Vanguard V-Twin models have the same
        > > > > crankshaft constraints. We also might be getting conflicting official
        > > > > versions and accurate insider know-how versions. Either way - due
        > > > > dilignece requires DOCUMENTATON.
        > > > >
        > > > >
        > > > > --- In Small4-strokeEngines@yahoogroups.com, "William Rich"
        > > > > williamrich1@ wrote:
        > > > > >
        > > > > >
        > > > > > Mr. Tinka, the Czech Republic pilot with the Vanguard powered SD-1,
        > > > > > shared with us earlier how Czech Republic B+S technical support
        > > > seemed
        > > > > > to indicate you can safely apply up to 250 lbs of outward thrust to
        > > > > the
        > > > > > flywheel end of the crankshaft. This was wonderful news! However, Al
        > > > > at
        > > > > > V-Twin Performance (site with motor sounds) finally responded to my
        > > > > > email with information from an American B+S engineer that is
        > > > > > contradictory. The engineer seems to says you CANNOT pull on
        > > > flywheel
        > > > > > side of crankshaft with force greater than 50 lbs!
        > > > > >
        > > > > > Here is my email exchange with Al and the B+S engineer:
        > > > > >
        > > > > > ---------------------------------
        > > > > > ----- Original Message ----- From: WilliamRich
        > > > > >
        > > > >
        > > > <mhtml:{3A2E637E-294D-4D22-AB7E-98231855CB44}mid://00000099/!x-usc:mailt\
        > > > \
        > > > > \
        > > > > > o:williamrich1@ To: vtwins@
        > > > > >
        > > > >
        > > > <mhtml:{3A2E637E-294D-4D22-AB7E-98231855CB44}mid://00000099/!x-usc:mailt\
        > > > \
        > > > > \
        > > > > > o:vtwins@ Sent: Monday, July 13, 2009 8:47 AM
        > > > > > Subject: Re: Air boat and similar V Twin propeller applications
        > > > > > Al, The ball bearing is on the PTO side and the sleeve bearing is on
        > > > > > the flywheel side (I'm sure you know this). Czech Republic B+S tech
        > > > > > support says you can pull outward on either end of the crankshaft up
        > > > > to
        > > > > > 250 lbs. The say you cannot push inward on either end of the
        > > > > crankshaft
        > > > > > with more than 50 lbs because the column of the crankshaft will
        > > > bend.
        > > > > > Your B+S engineering contact seems to say the net PTO outward thrust
        > > > > > must not exceed 500 lbs, and the net flywheel outward thrust must
        > > > not
        > > > > > exceed 50 lbs because the ball bearing handles thrust much better
        > > > than
        > > > > > the sleeve bearing. This could be a problem if your contact is
        > > > correct
        > > > > > because there are craft with tractor propellers pulling outward on
        > > > the
        > > > > > flywheel end of the crankshaft with a thrust of 150 lbs. William
        > > > Rich
        > > > > > ----- Original Message ----- From: vtwins@
        > > > > >
        > > > >
        > > > <mhtml:{3A2E637E-294D-4D22-AB7E-98231855CB44}mid://00000099/!x-usc:mailt\
        > > > \
        > > > > \
        > > > > > o:vtwins@ To: WilliamRich
        > > > > >
        > > > >
        > > > <mhtml:{3A2E637E-294D-4D22-AB7E-98231855CB44}mid://00000099/!x-usc:mailt\
        > > > \
        > > > > \
        > > > > > o:williamrich1@ Sent: Monday, July 13, 2009 8:33 AM Subject:
        > > > > > Re: Air boat and similar V Twin propeller applications
        > > > > > William, I hope this reply will help you answer some of your
        > > > > > questions. Al I was out on vacation and just catching up. The
        > > > > > axial bearing load capability is based on the type of surface that
        > > > the
        > > > > > thrust is applied to. The ball bearing on the PTO side can handle
        > > > 500
        > > > > > pounds of thrust and the sleeve bearing on the flywheel end can
        > > > handle
        > > > > > 50 pounds of thrust. If you have axial loads on both sides of the
        > > > > > engine, the net load is used to determine acceptance. For example,
        > > > if
        > > > > > you have 500 pounds axial load pulling on the PTO side and 500
        > > > pounds
        > > > > > pushing on the flywheel side, the net is 1000 pounds on the PTO side
        > > > > > which is excessive. If you have equivalent loads pulling on both
        > > > sides
        > > > > > of the engine, the net will be 0 and is acceptable. ----- Original
        > > > > > Message ----- From: WilliamRich
        > > > > >
        > > > >
        > > > <mhtml:{3A2E637E-294D-4D22-AB7E-98231855CB44}mid://00000099/!x-usc:mailt\
        > > > \
        > > > > \
        > > > > > o:williamrich1@ To: vtwins@
        > > > > >
        > > > >
        > > > <mhtml:{3A2E637E-294D-4D22-AB7E-98231855CB44}mid://00000099/!x-usc:mailt\
        > > > \
        > > > > \
        > > > > > o:vtwins@ Sent: Monday, July 06, 2009 4:32 PM
        > > > > > Subject: Re: Air boat and similar V Twin propeller applications
        > > > > > Thank you very much Al. ----- Original Message ----- From:
        > > > > > vtwins@
        > > > > >
        > > > >
        > > > <mhtml:{3A2E637E-294D-4D22-AB7E-98231855CB44}mid://00000099/!x-usc:mailt\
        > > > \
        > > > > \
        > > > > > o:vtwins@ To: WilliamRich
        > > > > >
        > > > >
        > > > <mhtml:{3A2E637E-294D-4D22-AB7E-98231855CB44}mid://00000099/!x-usc:mailt\
        > > > \
        > > > > \
        > > > > > o:williamrich1@ Sent: Monday, July 06, 2009 1:25 PM Subject:
        > > > > > Re: Air boat and similar V Twin propeller applications
        > > > > > William, I have forwarded your info request to a friend of mine who
        > > > > > is an application engineer at Briggs. He is on vacation till the
        > > > 13th
        > > > > of
        > > > > > July. I'll forward any helpfull info that he offers. Thanks,
        > > > > > Al ----- Original Message ----- From: WilliamRich
        > > > > >
        > > > >
        > > > <mhtml:{3A2E637E-294D-4D22-AB7E-98231855CB44}mid://00000099/!x-usc:mailt\
        > > > \
        > > > > \
        > > > > > o:williamrich1@ To: vtwins@
        > > > > >
        > > > >
        > > > <mhtml:{3A2E637E-294D-4D22-AB7E-98231855CB44}mid://00000099/!x-usc:mailt\
        > > > \
        > > > > \
        > > > > > o:vtwins@ Sent: Monday, July 06, 2009 3:30 PM
        > > > > > Subject: Air boat and similar V Twin propeller applications
        > > > > > Sirs, I know you run a business and your time is precious - what we
        > > > > > are interested in is your performance products (of course!), and any
        > > > > > strengthening of the drive train that you might deem appropriate to
        > > > > > handle direct-drive propeller loads. The Vanguard V-Twin
        > > > Applications
        > > > > > Manual has a crankshaft load table that defines the axial load limit
        > > > > as
        > > > > > 50 lbs inward and 500 lbs outward. I don't know if the outward limit
        > > > > of
        > > > > > 500 lbs applies to pulling on both ends of the crankshaft, and the
        > > > 50
        > > > > lb
        > > > > > inward limit applies to pushing on both ends of the crankshaft; or
        > > > if
        > > > > > the limits apply to the PTO only. I have deduced that if the limits
        > > > > > apply to both ends, then the 50 lb limit is to prevent the
        > > > crankshaft
        > > > > > column from bending under compression. Otherwise, the different
        > > > axial
        > > > > > load limits - 50 lbs and 500 lbs - suggest that one bearing type,
        > > > > sleeve
        > > > > > or ball-bearing, withstands axial loads much better than the other.
        > > > > > All things considered, I suspect that pulling on the PTO with up to
        > > > > 500
        > > > > > lbs force is ok because the ball-bearing can take the axial rotary
        > > > > > compression, while pulling on the flywheel end is limited to 50 lbs
        > > > > > because the sleeve bearing does not take axial rotary compression
        > > > > well.
        > > > > > This is important because some builders are placing the propeller
        > > > hub
        > > > > on
        > > > > > the flywheel in tractor configuration (pulling). This is not good if
        > > > > > they are applying 150 lbs of force against a 50 lb limit - it will
        > > > > work
        > > > > > for a while then trouble. In any event, any light you can shed on
        > > > how
        > > > > > to best attach a direct-drive propeller to a V-Twin crankshaft would
        > > > > be
        > > > > > very much appreciated. We also are very interested in dual-plug
        > > > > > heads. You excellent reputation is well known and we look forward to
        > > > > > doing business with you. Best regards, William Rich
        > > > > > ---------------------------------
        > > > > >
        > > > > >
        > > > > >
        > > > > > [Non-text portions of this message have been removed]
        > > > > >
        > > > >
        > > >
        > >
        >
      • RV7 builder
        I d agree with you about flexing (I assume that you mean twisting) the crank, except that almost all industrial applications have the PTO opposite the
        Message 3 of 13 , Jan 2, 2013
          I'd agree with you about flexing (I assume that you mean twisting) the crank, except that almost all industrial applications have the PTO opposite the flywheel, on everything from wood chippers to generators.

          A much more significant issue is actual bending loads. That's where you need to look at the *length* of the bearing where the load is applied. Look at a/c engines' main bearings on the prop end. They are typically 4-5 inches long, & only 2+ inches in diameter. That keeps bending loads away from the crank throws.

          Having said that, the bending load (even including gyroscopic loads) for a small wood prop might not be enough to worry about, on either end of the engine. I've been told that Generac has a pto adapter for the crank end of the engine, too.

          Charlie

          On 01/02/2013 02:35 PM, Kev A wrote:
           

          You're right, acceleration would be different if the inertia was too different, with one end lagging and flexing the crank. With a flywheel on one end only, the other end can de stress itself and no nasty harmonics.

          Answer is to fit a Luciole type alloy spider in place of the flywheel, carrying the ring gear and one magnet and counterweight. Hardly any inertia and lots of heavy iron neatly disposed of.

          Generator could go on either side.

          I'd best shut up and go fix something; got a new trike coming from India to bolt my engine into, it is ten pounds lighter with the latest design changes.

          Cheers

          Kev

          --- In Small4-strokeEngines@yahoogroups.com, "Maldague" <jmmaldague@...> wrote:
          >
          > Taking advantage of the ball bearing seem to be just logic.
          > But that bearing is installed on the PTO side and there has also been comments on having mass of inertia installed at both ends of the crankshaft that would increase stress compare to having both the flywheel and the prop installed at the same side. Not sure if that is valid?
          >
          > Jmm
          >
          >
          > --- In Small4-strokeEngines@yahoogroups.com, "Kev A" <kevin@> wrote:
          > >
          > > Fetched up this old post as it contains useful info
          > >
          > > Seems like the PTO side is best to stand propeller pull, especially as the crank shoulder will be up against the double roll ball bearing.
          > >
          > > I've used a Challenge taper lock parallel sided bush to lock my pulley on the shaft, in the bigger sizes it will stand prop inertia loads
          > >
          > > Kev
          > >
          > >
          > > --- In Small4-strokeEngines@yahoogroups.com, "William Rich" <williamrich1@> wrote:
          > > >
          > > >
          > > > Let's look at the good news - both B+S sources and the B+S Vanguard
          > > > Application Book say the PTO can withstand at least a 250 lbs of outward
          > > > thrust (some say 500 lbs). Why not turn the motor around and mount the
          > > > tractor propeller on the PTO? I've always wondered how secure a mounting
          > > > the flywheel is anyway. I've believe the Volkswagen people mount the
          > > > hub on a shaft - maybe we can use one of their techniques?
          > > >
          > > >
          > > > --- In Small4-strokeEngines@yahoogroups.com, "William Rich"
          > > > <williamrich1@> wrote:
          > > > >
          > > > >
          > > > > What we need is more documentation. The only thing we have is the B+S
          > > > > application book in the Files folder. It supports the 50lb flywheel
          > > > > outward limit. I suspect not all Vanguard V-Twin models have the same
          > > > > crankshaft constraints. We also might be getting conflicting official
          > > > > versions and accurate insider know-how versions. Either way - due
          > > > > dilignece requires DOCUMENTATON.
          > > > >
          > > > >
          > > > > --- In Small4-strokeEngines@yahoogroups.com, "William Rich"
          > > > > williamrich1@ wrote:
          > > > > >
          > > > > >
          > > > > > Mr. Tinka, the Czech Republic pilot with the Vanguard powered SD-1,
          > > > > > shared with us earlier how Czech Republic B+S technical support
          > > > seemed
          > > > > > to indicate you can safely apply up to 250 lbs of outward thrust to
          > > > > the
          > > > > > flywheel end of the crankshaft. This was wonderful news! However, Al
          > > > > at
          > > > > > V-Twin Performance (site with motor sounds) finally responded to my
          > > > > > email with information from an American B+S engineer that is
          > > > > > contradictory. The engineer seems to says you CANNOT pull on
          > > > flywheel
          > > > > > side of crankshaft with force greater than 50 lbs!
          > > > > >
          > > > > > Here is my email exchange with Al and the B+S engineer:
          > > > > >
          > > > > > ---------------------------------
          > > > > > ----- Original Message ----- From: WilliamRich
          > > > > >
          > > > >
          > > > <mhtml:{3A2E637E-294D-4D22-AB7E-98231855CB44}mid://00000099/!x-usc:mailt\
          > > > \
          > > > > \
          > > > > > o:williamrich1@ To: vtwins@
          > > > > >
          > > > >
          > > > <mhtml:{3A2E637E-294D-4D22-AB7E-98231855CB44}mid://00000099/!x-usc:mailt\
          > > > \
          > > > > \
          > > > > > o:vtwins@ Sent: Monday, July 13, 2009 8:47 AM
          > > > > > Subject: Re: Air boat and similar V Twin propeller applications
          > > > > > Al, The ball bearing is on the PTO side and the sleeve bearing is on
          > > > > > the flywheel side (I'm sure you know this). Czech Republic B+S tech
          > > > > > support says you can pull outward on either end of the crankshaft up
          > > > > to
          > > > > > 250 lbs. The say you cannot push inward on either end of the
          > > > > crankshaft
          > > > > > with more than 50 lbs because the column of the crankshaft will
          > > > bend.
          > > > > > Your B+S engineering contact seems to say the net PTO outward thrust
          > > > > > must not exceed 500 lbs, and the net flywheel outward thrust must
          > > > not
          > > > > > exceed 50 lbs because the ball bearing handles thrust much better
          > > > than
          > > > > > the sleeve bearing. This could be a problem if your contact is
          > > > correct
          > > > > > because there are craft with tractor propellers pulling outward on
          > > > the
          > > > > > flywheel end of the crankshaft with a thrust of 150 lbs. William
          > > > Rich
          > > > > > ----- Original Message ----- From: vtwins@
          > > > > >
          > > > >
          > > > <mhtml:{3A2E637E-294D-4D22-AB7E-98231855CB44}mid://00000099/!x-usc:mailt\
          > > > \
          > > > > \
          > > > > > o:vtwins@ To: WilliamRich
          > > > > >
          > > > >
          > > > <mhtml:{3A2E637E-294D-4D22-AB7E-98231855CB44}mid://00000099/!x-usc:mailt\
          > > > \
          > > > > \
          > > > > > o:williamrich1@ Sent: Monday, July 13, 2009 8:33 AM Subject:
          > > > > > Re: Air boat and similar V Twin propeller applications
          > > > > > William, I hope this reply will help you answer some of your
          > > > > > questions. Al I was out on vacation and just catching up. The
          > > > > > axial bearing load capability is based on the type of surface that
          > > > the
          > > > > > thrust is applied to. The ball bearing on the PTO side can handle
          > > > 500
          > > > > > pounds of thrust and the sleeve bearing on the flywheel end can
          > > > handle
          > > > > > 50 pounds of thrust. If you have axial loads on both sides of the
          > > > > > engine, the net load is used to determine acceptance. For example,
          > > > if
          > > > > > you have 500 pounds axial load pulling on the PTO side and 500
          > > > pounds
          > > > > > pushing on the flywheel side, the net is 1000 pounds on the PTO side
          > > > > > which is excessive. If you have equivalent loads pulling on both
          > > > sides
          > > > > > of the engine, the net will be 0 and is acceptable. ----- Original
          > > > > > Message ----- From: WilliamRich
          > > > > >
          > > > >
          > > > <mhtml:{3A2E637E-294D-4D22-AB7E-98231855CB44}mid://00000099/!x-usc:mailt\
          > > > \
          > > > > \
          > > > > > o:williamrich1@ To: vtwins@
          > > > > >
          > > > >
          > > > <mhtml:{3A2E637E-294D-4D22-AB7E-98231855CB44}mid://00000099/!x-usc:mailt\
          > > > \
          > > > > \
          > > > > > o:vtwins@ Sent: Monday, July 06, 2009 4:32 PM
          > > > > > Subject: Re: Air boat and similar V Twin propeller applications
          > > > > > Thank you very much Al. ----- Original Message ----- From:
          > > > > > vtwins@
          > > > > >
          > > > >
          > > > <mhtml:{3A2E637E-294D-4D22-AB7E-98231855CB44}mid://00000099/!x-usc:mailt\
          > > > \
          > > > > \
          > > > > > o:vtwins@ To: WilliamRich
          > > > > >
          > > > >
          > > > <mhtml:{3A2E637E-294D-4D22-AB7E-98231855CB44}mid://00000099/!x-usc:mailt\
          > > > \
          > > > > \
          > > > > > o:williamrich1@ Sent: Monday, July 06, 2009 1:25 PM Subject:
          > > > > > Re: Air boat and similar V Twin propeller applications
          > > > > > William, I have forwarded your info request to a friend of mine who
          > > > > > is an application engineer at Briggs. He is on vacation till the
          > > > 13th
          > > > > of
          > > > > > July. I'll forward any helpfull info that he offers. Thanks,
          > > > > > Al ----- Original Message ----- From: WilliamRich
          > > > > >
          > > > >
          > > > <mhtml:{3A2E637E-294D-4D22-AB7E-98231855CB44}mid://00000099/!x-usc:mailt\
          > > > \
          > > > > \
          > > > > > o:williamrich1@ To: vtwins@
          > > > > >
          > > > >
          > > > <mhtml:{3A2E637E-294D-4D22-AB7E-98231855CB44}mid://00000099/!x-usc:mailt\
          > > > \
          > > > > \
          > > > > > o:vtwins@ Sent: Monday, July 06, 2009 3:30 PM
          > > > > > Subject: Air boat and similar V Twin propeller applications
          > > > > > Sirs, I know you run a business and your time is precious - what we
          > > > > > are interested in is your performance products (of course!), and any
          > > > > > strengthening of the drive train that you might deem appropriate to
          > > > > > handle direct-drive propeller loads. The Vanguard V-Twin
          > > > Applications
          > > > > > Manual has a crankshaft load table that defines the axial load limit
          > > > > as
          > > > > > 50 lbs inward and 500 lbs outward. I don't know if the outward limit
          > > > > of
          > > > > > 500 lbs applies to pulling on both ends of the crankshaft, and the
          > > > 50
          > > > > lb
          > > > > > inward limit applies to pushing on both ends of the crankshaft; or
          > > > if
          > > > > > the limits apply to the PTO only. I have deduced that if the limits
          > > > > > apply to both ends, then the 50 lb limit is to prevent the
          > > > crankshaft
          > > > > > column from bending under compression. Otherwise, the different
          > > > axial
          > > > > > load limits - 50 lbs and 500 lbs - suggest that one bearing type,
          > > > > sleeve
          > > > > > or ball-bearing, withstands axial loads much better than the other.
          > > > > > All things considered, I suspect that pulling on the PTO with up to
          > > > > 500
          > > > > > lbs force is ok because the ball-bearing can take the axial rotary
          > > > > > compression, while pulling on the flywheel end is limited to 50 lbs
          > > > > > because the sleeve bearing does not take axial rotary compression
          > > > > well.
          > > > > > This is important because some builders are placing the propeller
          > > > hub
          > > > > on
          > > > > > the flywheel in tractor configuration (pulling). This is not good if
          > > > > > they are applying 150 lbs of force against a 50 lb limit - it will
          > > > > work
          > > > > > for a while then trouble. In any event, any light you can shed on
          > > > how
          > > > > > to best attach a direct-drive propeller to a V-Twin crankshaft would
          > > > > be
          > > > > > very much appreciated. We also are very interested in dual-plug
          > > > > > heads. You excellent reputation is well known and we look forward to
          > > > > > doing business with you. Best regards, William Rich
          > > > > > ---------------------------------
          > > > > >
          > > > > >


        • George Bearden
          ... flywheel, on everything from wood chippers to generators. Charlie, at 1st glance, your examples do not have much of a cyclic load which is where the
          Message 4 of 13 , Jan 2, 2013

            > except that almost all industrial applications have the PTO opposite the flywheel, on everything from wood chippers to generators.

             

            Charlie, at 1st glance, your examples do not have much of a cyclic load which is where the torsion stress comes from.

          • RV7 builder
            Wood chipper? How about a zero-turn mower? Massive impulse loads. There s also the torsional resonance issue, which can be all over the map depending on the
            Message 5 of 13 , Jan 2, 2013
              Wood chipper? How about a zero-turn mower? Massive impulse loads.

              There's also the torsional resonance issue, which can be all over the map depending on the mass of the load & operating rpm.

              Charlie

              On 01/02/2013 03:09 PM, George Bearden wrote:
               

              > except that almost all industrial applications have the PTO opposite the flywheel, on everything from wood chippers to generators.

               

              Charlie, at 1st glance, your examples do not have much of a cyclic load which is where the torsion stress comes from.


            • Will Warren
              The PTO end would seem to be best for a tractor-pull set up but what about using this engine in a pusher type installation ?  Which end?    Best regards, 
              Message 6 of 13 , Jan 2, 2013
                The PTO end would seem to be best for a tractor-pull set up but what about using this engine in a pusher type installation ?  Which end?
                 
                 Best regards, 
                 Will   Warren   
                 
                 
                 
                 


                From: Maldague <jmmaldague@...>
                To: Small4-strokeEngines@yahoogroups.com
                Sent: Wednesday, January 2, 2013 1:26 PM
                Subject: [Small4-strokeEngines] Re: Vanguard V-Twin allowable thrust loads

                 
                Taking advantage of the ball bearing seem to be just logic.
                But that bearing is installed on the PTO side and there has also been comments on having mass of inertia installed at both ends of the crankshaft that would increase stress compare to having both the flywheel and the prop installed at the same side. Not sure if that is valid?

                Jmm

                --- In Small4-strokeEngines@yahoogroups.com, "Kev A" <kevin@...> wrote:
                >
                > Fetched up this old post as it contains useful info
                >
                > Seems like the PTO side is best to stand propeller pull, especially as the crank shoulder will be up against the double roll ball bearing.
                >
                > I've used a Challenge taper lock parallel sided bush to lock my pulley on the shaft, in the bigger sizes it will stand prop inertia loads
                >
                > Kev
                >
                >
                > --- In Small4-strokeEngines@yahoogroups.com, "William Rich" <williamrich1@> wrote:
                > >
                > >
                > > Let's look at the good news - both B+S sources and the B+S Vanguard
                > > Application Book say the PTO can withstand at least a 250 lbs of outward
                > > thrust (some say 500 lbs). Why not turn the motor around and mount the
                > > tractor propeller on the PTO? I've always wondered how secure a mounting
                > > the flywheel is anyway. I've believe the Volkswagen people mount the
                > > hub on a shaft - maybe we can use one of their techniques?
                > >
                > >
                > > --- In Small4-strokeEngines@yahoogroups.com, "William Rich"
                > > <williamrich1@> wrote:
                > > >
                > > >
                > > > What we need is more documentation. The only thing we have is the B+S
                > > > application book in the Files folder. It supports the 50lb flywheel
                > > > outward limit. I suspect not all Vanguard V-Twin models have the same
                > > > crankshaft constraints. We also might be getting conflicting official
                > > > versions and accurate insider know-how versions. Either way - due
                > > > dilignece requires DOCUMENTATON.
                > > >
                > > >
                > > > --- In Small4-strokeEngines@yahoogroups.com, "William Rich"
                > > > williamrich1@ wrote:
                > > > >
                > > > >
                > > > > Mr. Tinka, the Czech Republic pilot with the Vanguard powered SD-1,
                > > > > shared with us earlier how Czech Republic B+S technical support
                > > seemed
                > > > > to indicate you can safely apply up to 250 lbs of outward thrust to
                > > > the
                > > > > flywheel end of the crankshaft. This was wonderful news! However, Al
                > > > at
                > > > > V-Twin Performance (site with motor sounds) finally responded to my
                > > > > email with information from an American B+S engineer that is
                > > > > contradictory. The engineer seems to says you CANNOT pull on
                > > flywheel
                > > > > side of crankshaft with force greater than 50 lbs!
                > > > >
                > > > > Here is my email exchange with Al and the B+S engineer:
                > > > >
                > > > > ---------------------------------
                > > > > ----- Original Message ----- From: WilliamRich
                > > > >
                > > >
                > > <mhtml:{3A2E637E-294D-4D22-AB7E-98231855CB44}mid://00000099/!x-usc:mailt\
                > > \
                > > > \
                > > > > o:williamrich1@ To: vtwins@
                > > > >
                > > >
                > > <mhtml:{3A2E637E-294D-4D22-AB7E-98231855CB44}mid://00000099/!x-usc:mailt\
                > > \
                > > > \
                > > > > o:vtwins@ Sent: Monday, July 13, 2009 8:47 AM
                > > > > Subject: Re: Air boat and similar V Twin propeller applications
                > > > > Al, The ball bearing is on the PTO side and the sleeve bearing is on
                > > > > the flywheel side (I'm sure you know this). Czech Republic B+S tech
                > > > > support says you can pull outward on either end of the crankshaft up
                > > > to
                > > > > 250 lbs. The say you cannot push inward on either end of the
                > > > crankshaft
                > > > > with more than 50 lbs because the column of the crankshaft will
                > > bend.
                > > > > Your B+S engineering contact seems to say the net PTO outward thrust
                > > > > must not exceed 500 lbs, and the net flywheel outward thrust must
                > > not
                > > > > exceed 50 lbs because the ball bearing handles thrust much better
                > > than
                > > > > the sleeve bearing. This could be a problem if your contact is
                > > correct
                > > > > because there are craft with tractor propellers pulling outward on
                > > the
                > > > > flywheel end of the crankshaft with a thrust of 150 lbs. William
                > > Rich
                > > > > ----- Original Message ----- From: vtwins@
                > > > >
                > > >
                > > <mhtml:{3A2E637E-294D-4D22-AB7E-98231855CB44}mid://00000099/!x-usc:mailt\
                > > \
                > > > \
                > > > > o:vtwins@ To: WilliamRich
                > > > >
                > > >
                > > <mhtml:{3A2E637E-294D-4D22-AB7E-98231855CB44}mid://00000099/!x-usc:mailt\
                > > \
                > > > \
                > > > > o:williamrich1@ Sent: Monday, July 13, 2009 8:33 AM Subject:
                > > > > Re: Air boat and similar V Twin propeller applications
                > > > > William, I hope this reply will help you answer some of your
                > > > > questions. Al I was out on vacation and just catching up. The
                > > > > axial bearing load capability is based on the type of surface that
                > > the
                > > > > thrust is applied to. The ball bearing on the PTO side can handle
                > > 500
                > > > > pounds of thrust and the sleeve bearing on the flywheel end can
                > > handle
                > > > > 50 pounds of thrust. If you have axial loads on both sides of the
                > > > > engine, the net load is used to determine acceptance. For example,
                > > if
                > > > > you have 500 pounds axial load pulling on the PTO side and 500
                > > pounds
                > > > > pushing on the flywheel side, the net is 1000 pounds on the PTO side
                > > > > which is excessive. If you have equivalent loads pulling on both
                > > sides
                > > > > of the engine, the net will be 0 and is acceptable. ----- Original
                > > > > Message ----- From: WilliamRich
                > > > >
                > > >
                > > <mhtml:{3A2E637E-294D-4D22-AB7E-98231855CB44}mid://00000099/!x-usc:mailt\
                > > \
                > > > \
                > > > > o:williamrich1@ To: vtwins@
                > > > >
                > > >
                > > <mhtml:{3A2E637E-294D-4D22-AB7E-98231855CB44}mid://00000099/!x-usc:mailt\
                > > \
                > > > \
                > > > > o:vtwins@ Sent: Monday, July 06, 2009 4:32 PM
                > > > > Subject: Re: Air boat and similar V Twin propeller applications
                > > > > Thank you very much Al. ----- Original Message ----- From:
                > > > > vtwins@
                > > > >
                > > >
                > > <mhtml:{3A2E637E-294D-4D22-AB7E-98231855CB44}mid://00000099/!x-usc:mailt\
                > > \
                > > > \
                > > > > o:vtwins@ To: WilliamRich
                > > > >
                > > >
                > > <mhtml:{3A2E637E-294D-4D22-AB7E-98231855CB44}mid://00000099/!x-usc:mailt\
                > > \
                > > > \
                > > > > o:williamrich1@ Sent: Monday, July 06, 2009 1:25 PM Subject:
                > > > > Re: Air boat and similar V Twin propeller applications
                > > > > William, I have forwarded your info request to a friend of mine who
                > > > > is an application engineer at Briggs. He is on vacation till the
                > > 13th
                > > > of
                > > > > July. I'll forward any helpfull info that he offers. Thanks,
                > > > > Al ----- Original Message ----- From: WilliamRich
                > > > >
                > > >
                > > <mhtml:{3A2E637E-294D-4D22-AB7E-98231855CB44}mid://00000099/!x-usc:mailt\
                > > \
                > > > \
                > > > > o:williamrich1@ To: vtwins@
                > > > >
                > > >
                > > <mhtml:{3A2E637E-294D-4D22-AB7E-98231855CB44}mid://00000099/!x-usc:mailt\
                > > \
                > > > \
                > > > > o:vtwins@ Sent: Monday, July 06, 2009 3:30 PM
                > > > > Subject: Air boat and similar V Twin propeller applications
                > > > > Sirs, I know you run a business and your time is precious - what we
                > > > > are interested in is your performance products (of course!), and any
                > > > > strengthening of the drive train that you might deem appropriate to
                > > > > handle direct-drive propeller loads. The Vanguard V-Twin
                > > Applications
                > > > > Manual has a crankshaft load table that defines the axial load limit
                > > > as
                > > > > 50 lbs inward and 500 lbs outward. I don't know if the outward limit
                > > > of
                > > > > 500 lbs applies to pulling on both ends of the crankshaft, and the
                > > 50
                > > > lb
                > > > > inward limit applies to pushing on both ends of the crankshaft; or
                > > if
                > > > > the limits apply to the PTO only. I have deduced that if the limits
                > > > > apply to both ends, then the 50 lb limit is to prevent the
                > > crankshaft
                > > > > column from bending under compression. Otherwise, the different
                > > axial
                > > > > load limits - 50 lbs and 500 lbs - suggest that one bearing type,
                > > > sleeve
                > > > > or ball-bearing, withstands axial loads much better than the other.
                > > > > All things considered, I suspect that pulling on the PTO with up to
                > > > 500
                > > > > lbs force is ok because the ball-bearing can take the axial rotary
                > > > > compression, while pulling on the flywheel end is limited to 50 lbs
                > > > > because the sleeve bearing does not take axial rotary compression
                > > > well.
                > > > > This is important because some builders are placing the propeller
                > > hub
                > > > on
                > > > > the flywheel in tractor configuration (pulling). This is not good if
                > > > > they are applying 150 lbs of force against a 50 lb limit - it will
                > > > work
                > > > > for a while then trouble. In any event, any light you can shed on
                > > how
                > > > > to best attach a direct-drive propeller to a V-Twin crankshaft would
                > > > be
                > > > > very much appreciated. We also are very interested in dual-plug
                > > > > heads. You excellent reputation is well known and we look forward to
                > > > > doing business with you. Best regards, William Rich
                > > > > ---------------------------------
                > > > >
                > > > >
                > > > >
                > > > > [Non-text portions of this message have been removed]
                > > > >
                > > >
                > >
                >



              • Peter Walker
                Hello A wood chipper is pretty much a huge flywheel that sees large loads for a few seconds A zero turn mower has a  steady load on the blades
                Message 7 of 13 , Jan 2, 2013
                  Hello
                  A wood chipper is pretty much a huge flywheel that sees large loads for a few seconds A zero turn mower has a  steady load on the blades with occasional higher loads with a load limiter (a vee belt) with no harmonics The hydrostatic drive is a variable displacement pump with ramp up and down loads
                  A propeller is a spring that stores and releases energy as well as moving air Match the frequency and the energy spikes become destructive to the engine
                  Peter


                  From: RV7 builder <mcsophie@...>
                  To: Small4-strokeEngines@yahoogroups.com
                  Sent: Thursday, January 3, 2013 5:35 AM
                  Subject: Re: [Small4-strokeEngines] Re: Vanguard V-Twin allowable thrust loads

                   
                  Wood chipper? How about a zero-turn mower? Massive impulse loads.

                  There's also the torsional resonance issue, which can be all over the map depending on the mass of the load & operating rpm.

                  Charlie

                  On 01/02/2013 03:09 PM, George Bearden wrote:
                   
                  > except that almost all industrial applications have the PTO opposite the flywheel, on everything from wood chippers to generators.
                   
                  Charlie, at 1st glance, your examples do not have much of a cyclic load which is where the torsion stress comes from.




                • boxerbs
                  Last time we went through this my conclusions from the discussion were the prop/flywheel relationship did indeed work against each other, the PTO should have
                  Message 8 of 13 , Jan 3, 2013
                    Last time we went through this my conclusions from the discussion were the prop/flywheel relationship did indeed work against each other, the PTO should have an added thrust bearing if direct prop mount is used, and the in force used as pusher must be negated, again with the thrust bearing... Has this changed or what? :-)
                    Garry

                    --- In Small4-strokeEngines@yahoogroups.com, Peter Walker wrote:
                    >
                    > Hello
                    > A wood chipper is pretty much a huge flywheel that sees large loads for a few seconds A zero turn mower has a  steady load on the blades with occasional higher loads with a load limiter (a vee belt) with no harmonics The hydrostatic drive is a variable displacement pump with ramp up and down loads
                    > A propeller is a spring that stores and releases energy as well as moving air Match the frequency and the energy spikes become destructive to the engine
                    > Peter
                    >
                    >
                    > ________________________________
                    > From: RV7 builder
                    > To: Small4-strokeEngines@yahoogroups.com
                    > Sent: Thursday, January 3, 2013 5:35 AM
                    > Subject: Re: [Small4-strokeEngines] Re: Vanguard V-Twin allowable thrust loads
                    >
                    >
                    >  
                    > Wood chipper? How about a zero-turn mower? Massive impulse loads.
                    >
                    > There's also the torsional resonance issue, which can be all over
                    > the map depending on the mass of the load & operating rpm.
                    >
                    > Charlie
                    >
                    > On 01/02/2013 03:09 PM, George Bearden wrote:
                    >
                    >  
                    > >> except that almost all industrial applications have the PTO opposite the flywheel, on everything from wood chippers to generators.
                    > > 
                    > >Charlie, at 1st glance, your examples do not have much of a cyclic load which is where the torsion stress comes from.
                    > >
                    > >
                    >
                  • Kev A
                    Garry said ... *Mine is a pusher with multi v belt reduction, PTO side; this meant including fan and cowl. As the exhausts happen to be PTO side a larger than
                    Message 9 of 13 , Jan 6, 2013
                      Garry said
                      > Last time we went through this my conclusions from the discussion were the prop/flywheel relationship did indeed work against each other, the PTO should have an added thrust bearing if direct prop mount is used

                      *Mine is a pusher with multi v belt reduction, PTO side; this meant including fan and cowl. As the exhausts happen to be PTO side a larger than usual volume of cooling air is needed as it passes the cooler portion of the heads before reaching the hot exhaust side. If I was building a tractor aircraft free air cooled, the prop would be fixed to the PTO side, as then the prop is pulling the step on the crank directly against the double-row ball bearings in the cover. This also gives best temperature distribution as airflow runs from hottest side to the inlets and keeps carb icing down. Keep stock carb and manifold and fit a big scoop and you will also see ram-air increases in power.

                      The scares on propeller breaking cranks is most likely the same thing that makes two blade aircraft of any type shed their props, a three blade has a different behaviour. Not sure of the physics but there was an article on this in the UK a few years back, Moths and Austers were losing the full assembly off the front. Stick a two blade on a cast crank and that might be what is busting them. Easiest way to get peace of mind is a support bearing although the crank then has less area left to grip, or it a light three blade prop, I did.

                      The Luciole has the inlets at front, exhausts at back, dumps the flywheel and fits a prop instead; whilst Michael Columban is worshipped as a genius, I reckon that configuration was a mistake, and you often see Lucioles with wrapped inlet manifolds against the chill blast of air.

                      Kev
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