Still Looking for the correct fly wheel ring bolts

[Tinkerman]

Evening All:

I have been looking for what to me. would be the correct flywheel ring gear bolts. The bolts that I took off were grade 8, 5/16" X 24 by 1", partial thread. All I seem to be able to get are grade 5 in that size. Am I wrong in thinking that I'm cruisin for a bruisin by using the grade 5? Worrys me. What have any of you used? The original ones don't look too good. This is for a TR-3A.

Thanks, Tinkerman

 

[Guest]

Re: Still Looking for the correct fly wheel ring b

I don't think that grade 8 is enough. I would look for 12's. I am pretty sure that TRF has them.

Oh, and by the way, does anyone want or need a brand new ring gear for a TR6. Am I wrong in thinking that it should fit the 3 and 4 as well. Brand new, still has the cosmoline. Cheap.

 

[Guest]

Re: Still Looking for the correct fly wheel ring b

Wait, why do you have bolts holding your ring gear on? I thought this was pressed on. I was thinking about the clutch plate. 12's here.

 

[Bugeye58]

Re: Still Looking for the correct fly wheel ring b

Aircraft Spruce.
64 cents each with the head drilled for safety wire, Part Number AN5-7HA.
26 cents each undrilled, AN5-7A.

https://www.aircraftspruce.com/catalog/hapages/an5.php

Jeff

 

[TR3driver]

I don't believe they are particularly hard; I doubt the originals were better than Grade 5. This is low-tech stuff, they didn't use hardened (expensive) components unless they had to.

However, I note that the ring gear bolts did not have a 'standard' hardware part number, so there was something special about them. Possibly the shank diameter or length were specified as larger than usual.

TRF has them listed, P/N 112653.

Never seen or heard of anyone having trouble with those bolts (tho TS39781LO didn't have them until maybe 10 years ago when I converted to the later flywheel). So I'd worry more about them backing out under vibration, than not being strong enough for the job.

Both earlier and later TRs just used a press fit instead of bolts anyway (although the press fit does sometimes fail on a TR6).

 

[martx-5]

Grade 8 bolts should be fine. I've found them at my local ACE hardware store, but in the 1" length, they are threaded all the way. You may have to go to a longer size that is unthreaded at the hex, and cut them down. You can also get them at McMaster. Just search on 'cap screw' and it will walk you through the selection process. McMaster doesn't show a partially threaded screw until the 1-1/2" length.

Edit: To expand on Randalls thought about the vibration. I just looked at my flywheel, and noticed they have locking plates that fold up on the flats of the bolts, so apparently the Triumph engineers thought that they should be positively locked in place.

 

[TR3driver]

Re: Still Looking for the correct fly wheel ring b

Am I wrong in thinking that it should fit the 3 and 4 as well.

I'm pretty sure the TR6 ring gear is different than TR3-early 3A; and quite certain it's different than TR4. For one thing, the TR6 ring gear is pressed on, while the TR4 is held with bolts.

 

[martx-5]

Re: Still Looking for the correct fly wheel ring b

So is the TR4A, as I have one of those because I'm doing Herman's Toyota gearbox conversion, and it uses the TR4A-TR6 clutch pressure plate.

 

[DNK]

Re: Still Looking for the correct fly wheel ring b

Check ARP. Might be(read definitely) spendy

 

[Bugeye58]

Re: Still Looking for the correct fly wheel ring b

Check ARP. Might be(read definitely) spendy

I looked at the ARP site before I posted the Aircraft Spruce link, and didn't see anything listed. I checked APT, too.
Jeff

 

[DNK]

Re: Still Looking for the correct fly wheel ring b

call them they have a lot of stuff that is not listed.

 

[DougF]

Re: Still Looking for the correct fly wheel ring b

You would be best to replace them.
I was never a big believer in the thread stretching of a capscrew until I sat through a demonstration with the
Skidmore/Wilhelm equipment for the proper testing of used capscrews.
Lesser quality fasteners can lose 20+% torque after the initial tightening. The number drops significantly after each subsequent torqueing.
The tests I watched were with Grade 8 fasteners.
The parts I've always been concerned about are the threads in the casting.

 

[70herald]

Re: Still Looking for the correct fly wheel ring b

Check ARP. Might be(read definitely) spendy

I bought ARP head studs / nuts for the Herald and was surprised that they were CHEAPER than the Indian / Chinese stuff sold by the Triumph suppliers. I ordered from Summit Racing, and the part came straight from the ARP factory. Very good service and price. I think that you should call ARP and find out if they have the correct parts. If they have a part # call up Summit for a price.

Just one thing about the flywheel bolts, If they are the same as the 4 cyl versions, the diameter at the top is larger than the thread size.

 

[Tinkerman]

Re: Still Looking for the correct fly wheel ring b

Bill: the way I understand it the earlier 2's and 3's hsd pressed on rings while the later 3's had bolt on. The one in my engine was a bolt on.

Jeff: thanks for the Aircraft Spruce link, I found the bolts I need and am putting together an order of other grade 8 goodies that I need.

Appreciate all of your help!!!!!!

Tinkerman

 

[TR3driver]

Re: Still Looking for the correct fly wheel ring b

Bill: the way I understand it the earlier 2's and 3's hsd pressed on rings while the later 3's had bolt on.

Right. The change happened in mid-1959, and affected the flywheel, ring gear, starter and transmission/bellhousing. It's important to get the starter that matches the flywheel, as the gear diameters were changed (later starters had a bigger gear, so the ring gear was reduced accordingly). But it gets very confusing, since the flywheel & starter can be interchanged as a pair between early and late engines; as can the transmissions. It's not at all unusual to find swaps or even mismatched components.

I did it myself when I converted TS39781LO (which originally had the early flywheel/starter/gearbox) to a TR4A style clutch & TR6 gearbox (& suitable lightweight starter).

The bolt-on ring gear (and matching starter/bellhousing) continued to the end of TR4A production.