FLYWHEEL RING GEAR

[MICKBARRATT]

Hi all, has anyone fitted a new ring gear to a flywheel or know what sort of a job it is. I have a TR7-V8 which could do with a new one, ive seen them on rimmers reasonably priced but need to know if its a job i can do after i remove the engine.. Any help appreciated, thanks guys... Mick.......... :)

[JohnD]

You heat the ring until it is near red hot, so that expands enough to slip onto the cold flywheel.
I think that's it - I've no idea about TR7s.
Hard to get such a large object hot enough - I don't think they fit in an oven!
See: http://mgaguru.com/mgtech/clutch/ft_101.htm

Isn't that extraordinary? That's how cart wheels were given an iron 'tyre', and we still use the same technique.
What about moderns?

John

[Brian 93957]

Hi i worked for an engine reconditioner, and the procedure was the same for all ring gears.
First cut through the old ring gear with a hacksaw to split it and remove it from the flywheel.
Then we heated the new ring gear up with a gas torch to expand it using even heat all the way round. Then taking care to ensure the ring gear is the correct way round if there is a lead in for the starter teeth, place it over the flywheel and make sure its seated properly then leave to cool.
Not a hard job but you will need some heat to do it.
Hope that helps

[TRad]

I found the time taken to expose the TR7 ring gear was more of a pain than actually fitting it onto the flywheel!  (Its also much easier than putting an iron rim on a cartwheel - my family are wheelwrights and I know from experience that getting a red hot iron rim onto a wooden wheel quickly without it perishing the outer edge is a challenge in itself!)  ;D

[Beans]

8VC wrote:

... my family are wheelwrights and I know from experience ...

Didn't know you were that old  ;D

[MICKBARRATT]

Thanks guys, was pretty much what i expected... Ill let you know how it goes when i get round to doing it, in the meantime ill measure the oven... ha ha. All the best, Mick...

[TRad]

Yeah I'm older than Yoda!  ;D

[Lord Sorbington]

They don't always go on easily so if you struggle, most engineering workshops will fit it for a negligable fee.

[piman]

Hello John,

"you heat the ring until it is near red hot,"

I wouldn't be happy doing that, nor would I like heating it with a torch as it is too easy to soften the (hardened) teeth.

All ring gears I've fitted I've done cold. It is fiddly to keep them square but they will go on, you could use 'G' cramps I suppose but I just used a copper hammer.

Alec

[JohnD]

Wasn't me that suggested a gas axe, twas Brian.

I found this, a Ford Service note:
Service Letter Number:- 27
Dated:- 29th November 1966
Fitting a Flywheel ring gear - Cortina Range
Revised fitting instructions were issued.
When fitting a new ring gear it must be heated evenly to a temperature not exceeding 600� F (316�C) otherwise the ring gear's wear-resistant properties will be destroyed. If the ring gear is to be heated on a naked flame, place the ring gear on a bed of fire-bricks and then play the flame in a circular motion onto the bricks about 1/4 inch to 1/2 inch  from the inside of the gear until it reaches the required temperature.
DO NOT PLAY THE FLAME DIRECTLY ONTO THE RING GEAR !

The correct temperature can be detected by using either:
a temperature sensitive crayon or by polishing a section of the ring gear and heating it until it becomes Light Blue.
Fit the ring gear with the un-chamfered side (the thrust face) of the gear teeth on the left side when viewing from the front of the engine. Allow the ring gear to cool naturally. DO NOT QUENCH !

600degC is about half the annealing temp, so quite a large margin for error, as long as it is not locally heated as with a flame.

Some will put the flywheel in the deep freeze too!  But as a ring expands more than a solid wheel will contract, not worth going into battle with 'er indoors.  Some will use a barbecue, or build a fire around the ring, as a domestic oven isn't anything like hot enough - gas mark 9 is less than 250C.

John

[piman]

Hello John,

near red was your definition I quoted.

It's a long time since I did any heat treatment but it is very easy to take the hardness out. The Ford temperature you quote just above 300 degrees C, is a long way short of near red.

Certainly a bit of heat makes it easier to fit, albeit harder to handle as it makes the ring very heavy.

Alec

[MICKBARRATT]

Bit of conflicting info guys........ Ok,,, Alecs done em cold,,  Brians heated em with a blow torch... If its possible to fit cold wouldnt it make it be reasonably do-able if it was placed in a pre-heated fan assisted oven at 250 degrees and left until golden brown for 20-25 minutes(i could do chips at the same time)... Oh and fitted with a copper hammer... wacha reckon guys ????? :B :)

[piman]

hello Mick,

there will always be conflicting advice as there are different ways of achieving the same goal.

Pick the one, or a combination  that suits your facilities. There are pros and cons to every way.

Alec

[MICKBARRATT]

Yeah ill go along with that Alec, the methods left are mostly what i expected. Ill be having a go at it in the next few weeks and i really appreciate and thank everyone who took the time and trouble to reply to my thread.... Cheers, Mick........ 8)

[Brian 93957]

Hi Mick hope it goes well for you,  i would agree with others on here in that although i use heat to expand the ring gear , i dont need to get it anywhere near red hot in order to fit it, as it would affect ther hardening of the teeth. The main thing is to make sure you heat it evenly. Anyway good luck let us know how you get on.

[JohnD]

On the contrary, Alec, see any chart for tempering steel.
'Black heat',  just too cool to see it glowing in daylight, is about 600F.
How's that for 'near red hot'?
Sure, 'bright' red is nearly twice as hot.

John

[piman]

Hello John,

I don't suppose that there many on here who have the means to heat the ring to that temperature anyway? I do have Oxy\acetylene but chose not to use it, others will be happy to.

Alec

[JohnD]

How about:

Thick steel plate as 'griddle'.
Bricks and/or concrete blocks, to build a heat reflective oven on the griddle, big enough to slide the ring into, with space under the plate.
Heat the griddle with the gas axe from underneath, moving it around like Anton Mosimann making a sauce.  Well, he'd move the pan around on the gas, but you would have to move the flame.  OR, hire a 'tar furnace': http://www.hss.com/imagshop/guides/og_547.pdf

Buy an IR remote thermometer: http://cgi.ebay.co.uk/IR-Infrared-Digital-Thermometer-with-Laser-ECA01_W0QQitemZ280477416220QQcmdZViewItemQQptZUK_Baby_safety_Thermometers_ET?hash=item414dc1bb1c

John

[Lord Sorbington]

piman wrote:

Hello John,

I don't suppose that there many on here who have the means to heat the ring to that temperature anyway? I do have Oxy\acetylene but chose not to use it, others will be happy to.

Alec

Even if you do, there's still no guarantee it'll go on.

Like I say, the easiest option by far is to drop the ring gear and flywheel down to your local engine reconditioners, go and have a nice cup of coffee somewhere, maybe a cake too, pop back half an hour later, they'll have fitted the ring gear using a combination of heat and their big press or whatever and they'll charge you a fiver. Saves a lot of aggro.  :)

[Lord Sorbington]

Just one further thought, 2000mk2s are prone to the ring gear shifting to the point where the starter motor will no longer engage with it.

I'm not sure if TR7s can be similarly affected but if fitting a new ring gear I'd be very tempted to add a bit of loctite or a few tack welds to ensure it stays in place.

I read, in Practical Classics, about one guy who re seated his 2000's ring gear by drifting it back into place through a big hole he'd drilled in the bell housing; we eventually managed to re-seat one using a big hook shaped tool through the starter aperture although it took a long time to do so.  Still easier than removing the 'box. It is definately possible to get them into position when unheated.  Still, if I had the luxury of having the flywheel off the car I'd save some time and effort by taking it to a workshop!

[Beans]

sorbs wrote:

... I'm not sure if TR7s can be similarly affected ...

Never encountered that problem in 22 years of TR7 ownership  ::)

[Brian 93957]

I bought my mk2 PI as a non runner because the ring gear had moved, when i spoke to willmotts who made the replacement ring gear they said it was because Triumph used the same flywheel/ring gear for both inertia and pre-engaged starters. Trouble is because the later starter bendix travels the opposite direction from the inertia type its meshing with the ring gear from the wrong side to which it was designed for, so after a while, it can move. Whereas on a Tr7 this change over never occoured so no problems. Guess it was down to cost saving that the 2000/2.5 flywheel was never changed.

[mikew]

The automatics don't suffer from this problem because the ring gear is welded to the flexi drive plate

mike

[piman]

Hello Brian,

yes, it was the same ring gear but it can be fitted either way to suit an inertia or pre engaged starter. Why Triumph put them on back to front I don't know?

Alec

[Lord Sorbington]

93957 wrote:

I bought my mk2 PI as a non runner because the ring gear had moved, when i spoke to willmotts who made the replacement ring gear they said it was because Triumph used the same flywheel/ring gear for both inertia and pre-engaged starters. Trouble is because the later starter bendix travels the opposite direction from the inertia type its meshing with the ring gear from the wrong side to which it was designed for, so after a while, it can move. Whereas on a Tr7 this change over never occoured so no problems. Guess it was down to cost saving that the 2000/2.5 flywheel was never changed.

You should just have bump started it.  I once borrowed a Passat  for a few days which turned out to have a duff battery.  I could only park facing downhill so that I could bump start it.   :)

PIman, on the mk2s, the ring gear should sit against a lip on the flywheel.  The mk1 type starter would pull the ring gear towards the lip whereas the mk2 type pushes it away hence why they sometimes shift.  depends on production tolerances I suppose.