Lotus Elan

Lightweight Flywheel For Autocross

PostPost by: rickf » Mon Aug 09, 2004 2:55 pm

Anybody have any experience with lightweight flywheels, either aluminum or turned down? I use the car mostly for autocross with occasional street driving.
Cheers,<br>Rick<br>1972 Elan +2
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PostPost by: bill308 » Mon Aug 09, 2004 9:36 pm

I've used a Tilton aluminum flywheel in my S2 Elan for many years. Love it. The engine and car accelerate much faster without the additional inertia.
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PostPost by: rgh0 » Mon Aug 09, 2004 11:51 pm

Rick

I use a light weight steel flywheel in my historic racing Elan, I had to get a new flywheel to go with the Datsun 5 bolt steel crank so I thought I may as well make it a bit lighter. Its about 60% of the weight and maybe 40% of the rotational inertia of the standard flywheel. Its helps with engine acceleration but not so light that it affects idle smoothness.

I you really want to reduce the rotational inertia you need to also look at a small diameter multiplate racing clutch. Not so good for road use as very strongly on /off in their action. About half the rotational inertia of the clutch and flywheel is in the clutch assembly. I have not yet done this but its on my long term list of developments as time and money allow.

Be careful with modifications in this area, especially if you are building a high revving engine. The clutch and flywheel sit right next to your knees with only a bit of cast iron bell housing, very thin sheet metal chassis and fibreglass body to hold the bits in if they come apart. A good idea to put a substantial shield of steel or high strength aluminium between you and the flywheel / clutch asembly.

I have not seen the clutch in an Elan let go but I have seen it happen in a Ferrari Boxer when it destroyed the bell housing and shredded the top of the engine cover with clutch bits.

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PostPost by: lotus026 » Wed Sep 29, 2004 11:07 pm

I've had very good results with a lightened cast iron flywheel on my street & track driven '71 Datsun 510 (Nissan Bluebird for non USA people!), been driving it for about 15 years. Have to be a bit gentle with the clutch & throttle if you're just easing it away from a stop and want to be smooth, but no problem at all if you are doing a more aggressive start - and it sure does rev up in a hurry as opposed to how it was way back when! Think I lightened it about 5Kilos. I've also lightened the one on my Elan, but since I've been busy dealing with a front timing cover oil leak since installing it so far haven't really been able to find out how it behaves...though I'd think it might have been a real pain if I still had the original non-Sprint doughnuts; but I got rid of those and have CV joints now. Best modification that improved driveability I've done on the car!
Dave
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PostPost by: twincamracing » Fri Oct 01, 2004 3:40 am

I've run both lightweight steel and aluminum flywheels and they really do help the engine rev. You can go too light and not be able to launch the machine from a standstill. They also don't slow down the engine on deaccel like a heavy wheel does. If you are lightening a stock wheel take weight off the outside diameter and have the machinist radius any sharp corners from the cutting operation.. Have it balanced.

Scott
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PostPost by: tonyabacus » Sun Oct 03, 2004 2:59 pm

You could speak with Derek Matthews at Ark Racing near Stafford. Derek has been involved in making flywheels with integrated ring gear as well as specially manufacture of lightweight starter motors for many years. He has made for many of the big names in motorsport both here and abroad as well as us little folk.

A real nice guy to deal with and always helpful, because his business is making flywheels then he I am sure will have the right information regarding your questions.

Regards
Tony

ps his number is 01785 715234
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PostPost by: archigator » Fri Dec 24, 2004 1:09 am

I just had a Fidanza lightweight aluminum flywheel installed on my Elan Sprint, and I'm very happy with it. I was concerned about lack of driveability, but I have no problems at all taking off at a stop light or cruising slowly through a parking lot. Runs great! I'd recommend it to anyone looking for improved performance without compromising everyday driving.

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PostPost by: cabc26b » Mon Dec 27, 2004 4:21 pm

My vote would be for a lightweight steel one ( farndon ?? or tony ingram here in the states...)
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PostPost by: SJ Lambert » Sun May 20, 2012 7:33 am

I'm putting a Dave Bean supplied aluminium 104 tooth one into our open wheeler's second T/C motor. I think a few aluminium ones got used back in the sixties in similar applications, though I reckon there were probably more steel ones in racing cars back then.

Our open wheeler's original flywheel is a lightened iron one with a 7.25" clutch. Rev limit was probably 7500. I am yet to determine the upper limit for the aluminium one.

Does anyone know whether steel or aluminium first usurped iron?
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PostPost by: rgh0 » Sun May 20, 2012 11:48 am

Been using light weight steel flywheels for a few years -good for 9000 rpm at least from personal experience. Got an Aluminium one thats a little lighter and will try on my next engine to see how it works.

Most of the mass is in the outer edge to hold the ring gear in place so smaller diameter with smaller ring gear the way to go.

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PostPost by: SJ Lambert » Tue Aug 07, 2012 12:53 pm

I've checked with numerous major suppliers in Australia, none of them are able (or interested) to supply 30mm thick 7075-T6 temper structural aluminium plate in a say, 230 mm square section in order to turn down to a 90 tooth flywheel.

I've yet to trawl the Net in a "forensic" fashion, it currently feels like sourcing the raw material could nearly end up a more expensive exercise than purchasing a ready made steel one.

I don't suppose anyone knows of a specialty supplier that the raw aluminium could be sourced from?



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PostPost by: john.p.clegg » Tue Aug 07, 2012 4:32 pm

A by-product of EFI'ing looses a little weight...

John :wink:[attachment=0]efi flywheel.jpg[/attachment]
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PostPost by: memini55 » Thu Aug 09, 2012 1:01 pm

We have been auto crossing for about the last four or five years with an aluminum and it works out great. No issues of any kind and the motor is fairly tweaked with a few extra ponies.

Love the quick throttle responce!

Mark
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PostPost by: SJ Lambert » Thu Sep 13, 2012 11:03 pm

I've given up on 7075, but I can get 2024 T351 in Melbourne!!!

Carroll Smith reckons that Mac Tilton used 2024 in T3 or T4 temper as a better bet for flywheels than 7075 in any event.
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PostPost by: vstibbard » Fri Sep 14, 2012 3:28 am

James, Chequered Flag Racing in US, he advertises on the forum make aluminium flywheels, iv'e just purchased a 12 bolt one for elan, US$595 for whats its worth I had a steel one made recently for my 26r as it has a Cosworth 4 bolt steel crank (from new) with cast flywheel fitted by previous owner who used std clutch, cost close to 1000.00 in Australia to have it made.....

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