TR2/3/3A TR3 Ring gear

[prb51]

Does anyone know the internal diameter of the early sweat on flywheel ringear.
I've what I think is a replacement but it looks a tad small and I don't have the tranny off.

 

[TR3driver]

For the later, bolt-on gear, it's 9-7/8" (pretty close, didn't try to put calipers on it). I'd guess the early gear should be around 10-1/4" or maybe a skosh smaller.

 

[prb51]

Randall,
I guess I'm ok then as it's just a hair over 10.5 "...it just looked small for some reason.
Thanks

 

[TR3driver]

If it's any consolation, I had the same problem ... even accused ARE of selling me a Spitfire gear

 

[prb51]

I think that's because the flywheel is so friggin massive it left an impression of a larger unit than it actually is.
If I take the time to replace the ring gear (the new hi torque starter isn't sticking even though the ring teeth are a bit chewed up) someday I'll get that thing lightened/balanced to 17 lbs. or so.

 

[TR3driver]

FWIW, Joe Alexander (ARE) sells a new lightweight CNC flywheel that is a work of art. Don't recall the weight offhand, but it's pretty light and most of the weight is inwards at the hub & friction surface. But it's TR4A pattern, which means later starter and bolt-on ring gear (ARE also sells a lightened ring gear) plus a 4A clutch & TOB. Hmm, don't see it on the web site, so maybe they are all gone. But you could ask Joe, he might know of one or two still available; or perhaps be about ready to make another run of them.
https://www.the-vintage-racer.com/

I was running an alloy flywheel (from Jim Donato) and it really made a remarkable difference. Made the car much peppier and nimble, especially in first & second gear; even with an otherwise stock engine. But ISTR it was even lighter than the steel ones Joe sells.

Also FWIW, one of our local club members was able to get the part to convert his gear-drive starter from early to late. Don't recall the contact info offhand where he got the new pinion gear, but I can ask him the next time I see him.

 

[prb51]

I'll keep the original flywheel and have it worked over. That'd be much simpler.
What weight were you running?
I said 17lbs because that was the rec. in the "How to Improve TR2-TR4a" book, I'm guessing this is a comprimise weight for an otherwise stock/unbalanced motor.

 

[TR3driver]

What weight were you running?

Sorry, don't recall. But likely similar to the Fidanza, which is listed at 10 pounds in their catalog (plus the ring gear of course). It's not overall weight that counts anyway, but rotational inertia. 10 pounds at the rim is a lot different than 10 pounds at the hub.

 

[TR4nut]

Joe may not have the custom flywheels handy, but he routinely offers lightened and balanced stock flywheels at 17 lbs. And as weighty as they are, I can tell you they fit nicely in the USPS flat rate boxes so can be mailed for about $10 or so.

Randy