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• I’ve got the flywheel down from 7.7 kilos or about 17 pounds, down to 4.65 kilos, 10pounds 4 ounces, trouble is, cast iron is a brittle material. Trying to
Message 1 of 77 , Feb 1, 2012
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I’ve got the flywheel down from 7.7 kilos or about 17 pounds, down to 4.65 kilos, 10pounds 4 ounces, trouble is, cast iron is a brittle material. Trying to calculate what can be safely removed is difficult, the magnets force outwards at high revs, but don’t contribute to the strength of the flywheel rim. So the calculation is to see what weight of magnets relative to what depth of cast iron rim needed to restrain both itself and the magnets. I plumped for 16mm of C.I. to carry about 10m of magnets, but the bozo who machined misunderstood taking 12mm off and removed 18 instead, leaving only ten to carry the magnets, about 3/8” in US money. Has he done me a favour or created a dangerous situation? Aim to spin test the flywheel today to 6000, hope it works. Propeller will limit the ultimate speed nicely without needing a governor.

This was done by milling the rim away, but leaving the starter ring gear in place, forming a nice strong retaining hoop. I also didn’t take anything off the face as the Germans do, as this would reduce the support to the rim as well, the face is only 5/16” thickness at best. Left a lump of iron opposite the magnet same size, to drill or grind away for balancing.

When doing the sums it turns out that the force trying to burst the ‘wheel is not a straight line; one pound spinning at 5,000 is pressing out at 2,320.36 lbf, whereas the same weight at 6000 presses outwards 3,341.31 lbf, or 44% greater for an increase in spin rate of 20%. Plainly the mudboat folk who restrict stock revs to 5,100 know what they’re doing. Incidentally, when reading the handbook they do state that on generators the revs can fluctuate up to 4,200, so 4k is too low an ambition. Also researched hoop stress, this can be worked any number of ways but the stress at worst was 43 at 5000, for a yield of 113, with a recommendation to use only 65% of that, or 74.

If I was spinning a prop bolted to the flywheel and wanted a generator, and the prop was spinning at max say, 3000 then milling away the rim carefully is a pretty OK option; the guys who warn (rightly) about safety are aiming their comments at kart racers who could be injured badly by a grenading flywheel when they hop the driving tyres and go past 7,000rpm, or have hacked lumps off their flywheel.

One pound spinning at 3000 is only 835.3 pounds force outwards, only a third of the force at 5,000rpm, so maybe going to the trouble of losing your generator and buying an expensive alloy flywheel with only ignition on board, plus the extra weight and fuss of adding a generator somewhere else, is not as good as getting an expert to machine seven pounds off the stock item. I am spin testing mine and would pray everyone else does if they go this route.

Will report what happens today

Kev

PS some big disc grinders spin at 6000 according to the label in our local toolstore, could a flywheel be bolted to one via an adapter plate,, and set up behind some trees on a trestle? You could switch it on via an extension lead and stay the other side of the trees...;-)

From: Small4-strokeEngines@yahoogroups.com [mailto:Small4-strokeEngines@yahoogroups.com] On Behalf Of hufisch2004
Sent: 31 January 2012 22:29
To: Small4-strokeEngines@yahoogroups.com
Subject: [Small4-strokeEngines] Re: New Redrive

hello kevin,I have an ARC aluminum flywheel for my vanguard also with no generator magnets so what I did was heat an original cast iron wheel until the magnets came out easily and glued them into the aluminum flywheel.in order to make the bond real strong I used epoxy at 150 degrees centigrade.now what this did was destroy the magnet that triggers the ignition coil.replaced it with a number of heatresistant neodyme magnets.on a test run the setup for the ignition worked a treat but two of the glued-in generator magnets came loose without doing any damage.now i plan to replace those with an aluminum ring bored to accept neodymes.will take a while.

The moral of this story,the moral of this song is to never heat where heat does not belong
hufisch

--- In Small4-strokeEngines@yahoogroups.com <mailto:Small4-strokeEngines%40yahoogroups.com> , Kevin Armstrong <kevin@...> wrote:
>
> Hello Norm, following this with interest
>
> Every one of the aftermarket steel or alloy flywheel I've seen so far, only have the ignition magnet in the outer rim, aviators need long term power feed and tractor pullers don't, but the folk making these units are aiming for the tractor and kart racing market.
>
> I'm in the same fix with a Briggs Vanguard 23 hp, to slip under the UK equivalent of the FAR103 rules you have to take a smallblock unit and tune it up, rather than just buy a 35 hp off the shelf. Even worse, my aircraft needs a pusher prop and 40 hp, so a redrive and therefore a flywheel are required, all adding weight.
>
> So far the redrive is coming out at around 4-5 ( just under 10lbs) kilos in alloy, with some spare strength in the sums to cope with prop out of balance and fatigue. The standard cast iron wheel is in a machine shop being shaved on the outer rim, but only down to the same base depth of the recess that carries the ignition magnet, this is the weakest part of the 'wheel and removing outer rim mass is going to make the thing safer as there is less force hauling at that weakest point. The starter ring gear will also help hold the iron together at higher revs as it is tough steel and shrunk on.
>
> We don't need that high a power Wattage unless flying in Canada in Winter with heated clothing, and the 16 amps the B&S Vanguard alternator puts out seems over the top.
>
> Maybe a small generating coil or two could be mounted running close to the outside of the flywheel, they would put out a couple of weak pulses per revolution, and if it was hooked up to a smoothing capacitor and used to trickle charge the battery via a regulator, maybe we can all trash the heavy stock flywheel?
>
> Kev
>
> UK
>
> Ps what about a small motorcycle unit, say off a kid's motorbike, bolted onto the belt pulley face? Brackets would be really easy to set up on spacers.
>
>
> On 24 Jan 2012, at 18:57, "Norman" <nlheista@...> wrote:
>
> > Yes. The light flywheel from http://midwestsupercub.net/MWSC%20Catalog.pdf has part iron and part aluminum so retains the standard alternator and starter ring.
> >
> > I am thinking a machine shop could cut the standard steel flywheel
> > down from 20lbs to 10lbs and retain the alternator, ignition and starter ring. I will investigate.
> >
> > Norm Heistand
> >
> > --- In Small4-strokeEngines@yahoogroups.com <mailto:Small4-strokeEngines%40yahoogroups.com> , "dagwodzz@" <dagwodzz@> wrote:
> > >
> > > Hi Norm:
> > > By using the lighter aluminum flywheel are you able to keep the charging
> > > system?
> > >
> > >
> > > Darrell
> > >
> > >
> > >
> > >
> > > -------Original Message-------
> > >
> > > From: Norman
> > > Date: 1/24/2012 11:42:13 AM
> > > To: Small4-strokeEngines@yahoogroups.com <mailto:Small4-strokeEngines%40yahoogroups.com>
> > > Subject: [Small4-strokeEngines] Re: New Redrive
> > >
> > >
> > >
> > > My Kohler 25hp weighs 85lbs after the fan and shrouds are stripped off
> > > including exhaust pipes I added. I am adding 10lbs with the redrive and
> > > planning to subtract 10lbs by using a lighter flywheel. So I have an 85lb
> > > engine ready for propeller. This is the same weight as the 37hp 1/2 VW which
> > > turns a 54 x 22 prop direct drive. I will use a wood 60 x 26 prop which is
> > > optimum for a Rotax 277 running the 2.58:1 gearbox. I am using 1.6:1 redrive
> > > hoping to turn the prop the same rpm as the Rotax 277. I am hoping to get
> > > about the same static thrust as the 1/2 VW and the Rotax 277.
> > >
> > > I will be sharing the rpm and thrust numbers as soon as I get a prop. I will
> > > have a large grin if I get the numbers I want. Anyone know of a Rotax277
> > > prop for sale?
> > >
> > > Norm Heistand
> > >
> > > --- In Small4-strokeEngines@yahoogroups.com <mailto:Small4-strokeEngines%40yahoogroups.com> , "Paul Smigel" <paul.smigel@>
> > > wrote:
> > > >
> > > >
> > > > Norman,
> > > >
> > > > Please share with us some of the specs on your engine.
> > > >
> > > > what did you end up with for an all up weight on the engine / redrive.
> > > >
> > > > Once you get the prop on share with us what max rpm and at what prop size
> > > / pitch you are running and your thrust numbers with that setting.
> > > >
> > > > Thanks
> > > >
> > > > Paul
> > > > Any Air Time is a Great Time!
> > > > http://www.ulflyer.com/weedhopper/
> > > >
> > > >
> > > > --- In Small4-strokeEngines@yahoogroups.com <mailto:Small4-strokeEngines%40yahoogroups.com> , "Norman" <nlheista@> wrote:
> > > > >
> > > > > I have uploaded photos of my new belt reduction drive to the Photos area
> > > in an album titled Redrive. This unit is my own design for my 25hp Kohler
> > > V-Twin going on my Weedhopper ultralight I am building from plans. The
> > > photos show my prototype which I am testing. A 3/8 inch aluminum plate about
> > > 8 by 10 inch is bolted to the engine face using the 4 bolts around the power
> > > output shaft. The power pulley is a 22 tooth Gates. The driven pulley is a
> > > 35 tooth Gates giving a 1.6 to 1 ratio. The driven pulley is mounted on a 1
> > > inch shaft that runs with 2 ball bearing units. An MX Quicksilver prop hub
> > > is mounted on the shaft also.
> > > > >
> > > > > This setup should turn the same prop at the same rpm as a Rotax 277 with
> > > the B gearbox with 2.58 to 1 ratio. Many of the V-Twin industrial engines
> > > have the same bolt pattern around the power output shaft so this redrive
> > > should work for Kohler, Briggs, and Generac engines. Maybe all of them from
> > > 18hp to 40hp. The optimum propeller length and pitch will depend on the
> > > engine power. I designed my setup to use the same 2-blade wood prop that is
> > > optimum for the Rotax 277.
> > > > >
> > > > > The Gates PowerGrip GT2 is the best belt I found in my research. My unit
> > > uses a 30mm wide belt running on Gates pulleys. I believe this unit requires
> > > no maintenance once it is installed properly. I had considered an idler
> > > pulley to set the belt tension, but my testing is indicating that no idler
> > > is needed if the assembly uses a short belt and the pulley mounts give the
> > > belt a snug fit. The Gates pulleys and belts are available from 20mm to
> > > 100mm. I believe the 100mm is good for 200hp and the 30mm is good for 60hp.
> > > > >
> > > > > For flying we love extra strength so my 25hp should allow the 30mm belt
> > > to run a long time. The complete redrive assembly weighs about 10 lbs. After
> > > testing my prototype, I will reduce the plate to 6 in wide. This is mostly
> > > cosmetic. Once proven, I plan to sell some of these units for about \$500.
> > > This is much less cost and weight than all the belt redrive units I have
> > > found in my reserach.
> > > > >
> > > > > Norm Heistand Waiting for winter to be over.
> > > > >
> > > >
> > >
> > >
> > >
> > > Acrobatic hoopster's incredible shot
> > > A high school player makes a great save of a ball going out of bounds, only
> > > to get a big surprise.
> > >
> > >
> > >
> > > [Non-text portions of this message have been removed]
> > >
> >
> >
>
>
> [Non-text portions of this message have been removed]
>

[Non-text portions of this message have been removed]
• Patrick I think your concerns with spinning a wheel hub bearing (tapered roller or Timkin) at 2k+ rpm are unfounded. These are very lightly loaded compared to
Message 77 of 77 , Feb 6, 2012
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Patrick

I think your concerns with spinning a wheel hub bearing (tapered roller or Timkin) at 2k+ rpm are unfounded. These are very lightly loaded compared to what they see in the 'real world'. If we were spinning at 15K it might have an appreciable impact to the L life numbers, but at 2k, I think the most that might happen is you'll sling a little grease.
I know I am not doing much here to allay your fears here but consider that when they _DO_ fail, you'll likely have plenty of warning; they'll gradually get 'loose' which you'll notice as an increased vibration, kinda like how they fail on your car...

155/80 r13 = small trailer tire, diameter = 22.8.

This is ~910 revs/mile

at 60 mph this is 910rpm or 5280 ft / min

Circumference = 2Pi*r or Pid= 72 inches = 6ft

5280/6 = 880

So, 900 rpm is probably 'normal' for an auto wheel bearing.

What exactly are you fears with spinning these 'too fast'? They can't really fly apart. All they can really do is lose lube and wear out too soon. In an auto these commonly go 100K miles and more.

If you calculate the L10 life, even considering that we are spinning these at 2.5x the automobile speed, please consider that these are also VERY lightly loaded. The industry standard usable bearing lifespan (in rpm) is inversely proportional to the bearing load cubed.

In the ppg world, I am more concerned with the common use of radial row bearings with no special accommodation for the thrust load, but in practice this seems to not be an issue. These also seem to have a graceful failure with plenty of warning.

Mike Phillips
PBThrust.com

--- In Small4-strokeEngines@yahoogroups.com, Patrick Panzera <editor@...> wrote:
>
> I too am concerned with 1) the automobile axle bearing, that in the
> car, rarely ever seem more than 1000 rpm, and the cantilever of the
> upper assembly and 2) there must be a way to add an additional brace
> to keep the system from flexing, or worse, setting up a destructive
> harmonic.
>
> On Thu, Jan 19, 2012 at 10:23 AM, Jeron Smith <raven_redrives@...> wrote:
> > Norm
> >
> > Good to see someone working things out for the Do-it-Yourselfers.  Couple of free tips after doing belt redrive design for 17 years now.  Get hold of one of the Gates drive design handbooks and double check the HP rating for the 30mm belt at your small 22T diameter and RPM.  This is what determines the actual HP rating of the drive and for aircraft  you need this safety factor.  Also get rid of the extended canteliver on the crankshaft with the pulley so far out.  Bigger bottom and top sprocket, bearing stack on prop side of your adapter plate, bury the bearing stack behind the larger sprocket to get rid of most of the cantilevered load paths.  That should do it except for the unknowns of how the crank is going to handle the twisting with the prop at one and and flywheel at the other.  Only time will tell....  once you get a few hundred hours on it with a number of different props, you will see if there are any obvious problems.  Good luck on
> >
> > Hope this helps.
> >
> > Jeron Smith
> > Raven ReDrives Inc.
> >
> > --- On Tue, 1/17/12, Norman <nlheista@...> wrote:
> >
> > From: Norman <nlheista@...>
> > Subject: [Small4-strokeEngines] New Redrive
> > To: Small4-strokeEngines@yahoogroups.com
> > Date: Tuesday, January 17, 2012, 9:40 AM
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >      I have uploaded photos of my new belt reduction drive to the Photos area in an album titled Redrive. This unit is my own design for my 25hp Kohler V-Twin going on my Weedhopper ultralight I am building from plans. The photos show my prototype which I am testing. A 3/8 inch aluminum plate about 8 by 10 inch is bolted to the engine face using the 4 bolts around the power output shaft. The power pulley is a 22 tooth Gates. The driven pulley is a 35 tooth Gates giving a 1.6 to 1 ratio. The driven pulley is mounted on a 1 inch shaft that runs with 2 ball bearing units. An MX Quicksilver prop hub is mounted on the shaft also.
> >
> >
> >
> > This setup should turn the same prop at the same rpm as a Rotax 277 with the B gearbox with 2.58 to 1 ratio. Many of the V-Twin industrial engines have the same bolt pattern around the power output shaft so this redrive should work for Kohler, Briggs, and Generac engines. Maybe all of them from 18hp to 40hp. The optimum propeller length and pitch will depend on the engine power. I designed my setup to use the same 2-blade wood prop that is optimum for the Rotax 277.
> >
> >
> >
> > The Gates PowerGrip GT2 is the best belt I found in my research. My unit uses a 30mm wide belt running on Gates pulleys. I believe this unit requires no maintenance once it is installed properly. I had considered an idler pulley to set the belt tension, but my testing is indicating that no idler is needed if the assembly uses a short belt and the pulley mounts give the belt a snug fit. The Gates pulleys and belts are available from 20mm to 100mm. I believe the 100mm is good for 200hp and the 30mm is good for 60hp.
> >
> >
> >
> > For flying we love extra strength so my 25hp should allow the 30mm belt to run a long time. The complete redrive assembly weighs about 10 lbs. After testing my prototype, I will reduce the plate to 6 in wide. This is mostly cosmetic. Once proven, I plan to sell some of these units for about \$500. This is much less cost and weight than all the belt redrive units I have found in my reserach.
> >
> >
> >
> > Norm Heistand  Waiting for winter to be over.
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> > [Non-text portions of this message have been removed]
> >
> >
> >
> > ------------------------------------
> >
> >
> > ### Lets use this list to build a knowledge base for those who are
> > interested in flying with these engines. Don't forget you can search the
> > messages archive for past discussions. Please keep comments on subject.
> > Sorry, no attachments allowed.
> >
> >>http://groups.yahoo.com/group/Small4-strokeEngines/<
> >
> >
> >
> >
>
>
>
> --
> Thanks!
>
> Patrick Panzera
> Editor@...
> www.ContactMagazine.com
> http://www.eaa.org/experimenter/
> PPanzera@...
>
>
> --
> Thanks!
>
> Patrick Panzera
> Editor@...
> www.ContactMagazine.com