Ring Gear

[martinbrowning]

Good afternoon,

Currently engaged in a full rebuild of the engine from my 1972 S130. I will be renewing the ring gear whilst I have the opportunity but - the workshop manual makes it sound really easy and I presume that the gear can be heated in a domestic oven (wife out of course!!).

Can anybody tell me if it really is that easy or should I entrust the work to a local engine machine shop? (Aware that the words "easy" and "Lotus" are rarely found in the same phrase).

Thanks

Martin B

[john.p.clegg]

Martin
While she's out,put the flywheel in the freezer and the ring gear in the oven,be confident,you have to do it right first time,make sure you know which way round it goes...

John

[types26/36]

Martin, I have fitted them before with an oxy acetylene torch but I no longer have that option and will probably have one to fit in the near future so I am interested in the replies, here is a thread that makes it sound quite easy but the more info the better.
elan-f15/fitting-starter-ring-gear-t19618.html

[CBUEB1771]

Replacing the ring gear is pretty easy. From page 32 of Section E of the workshop manual:

"Heat the new ring gear evenly, to a temperature NOT EXCEEDING 600 F (316 C). Do NOT heat beyond this point otherwise the wear resistance properties of the gear will be destroyed. Fit the gear to the flywheel with the chamfers on the leading faces of the teeth relative to the normal direction of rotation. Allow the ring gear to cool naturally in the air. DO NOT QUENCH."

I have done it with no difficulty using an oxyacetylene torch with a heating tip. Putting the flywheel in the freezer might cause the ring gear to cool too quickly and affect the heat treatment of the gear. I say might, not definitely.

[gerrym]

Don't worry about the cold flywheel affecting the heat treatment of the ring gear, at less than 316 degrees C, the steel of the ring gear will be below the transition temperature. i.e it won't matter how fast it's subsequently cooled.

Regards
Gerry

[Foxie]

Martin
Make sure you know which way round it goes...

John

I scratched my head reading this, as I have changed from the Lucas to a pre-engaging type starter.

As it happens, both my original 1970 engine which had a Lucas starter, and my Tall Block built in 2003 with a pre-engaged starter are both out on the floor at the moment.

The 1970 engine has chamfers only on the rear edge, while the later type is chamfered on both sides.
The all the chamfers face the direction of rotation.

So the later ring gear is chamfered on both sides, but can still be fitted the wrong way round

Hope this helps

[CBUEB1771]

Don't worry about the cold flywheel affecting the heat treatment of the ring gear, at less than 316 degrees C, the steel of the ring gear will be below the transition temperature. i.e it won't matter how fast it's subsequently cooled.

Regards
Gerry

I tend to agree but Lotus says "DO NOT QUENCH" for some reason.

[fatboyoz]

Martin,
Know this is not the answer to your question, but worthwhile bearing in mind. If you swap to a pre-engaged type starter motor, it will engage on the other (presumably undamaged) side of the ringgear. The Lucas starter engages from the rear of the ringgear, the pre-engaged starter engages from the front. Make sure you get full engagement of the starter gear teeth on the ringgear if you go down the pre-engaged route.
Colin.

Good afternoon,

Currently engaged in a full rebuild of the engine from my 1972 S130. I will be renewing the ring gear whilst I have the opportunity but - the workshop manual makes it sound really easy and I presume that the gear can be heated in a domestic oven (wife out of course!!).

Can anybody tell me if it really is that easy or should I entrust the work to a local engine machine shop? (Aware that the words "easy" and "Lotus" are rarely found in the same phrase).

Thanks

Martin B

[twincamman]

OK I just did this job ----hack sawed the ring gear a bit and then hit it with a cold chisel to remove the old ring gear -----heated the new gear with a cutting torch BUT DONT ADD OXYGEN just acetylene ---the barby idea didn't work --the oven didn't work --a welding torch tip didn't work ----just the cutting head -----the ring dropped on and will self center as it cools so don't move it ----I also oil quenched the ring as it cooled to be safe -- --works a treat takes 15 minutes -----have at it --put the motor back in by setting the oil pan on the jack with a piece of wood and slide it into position --ED

[carrot]

Just a note of caution. If you've changed/exchanged the starter motor your new one will probably have a 9 tooth bendix. The ring gear is designed for a 10 tooth bendix and even though a 9 toother will turn it somewhat, it will tend to seize giving the symptoms of a jammed starter motor. Make sure you have a 10 tooth bendix or more importantly the correct one for the ring gear.

[twincamman]

NOT ON MINE ---i used a 9 tooth lucas [ as the problem was caused by a nisan denso ] -----I advise to stay with the 9 tooth starter gear --I have timed the engine so it fires up on the first revolution thus saving a lot of grinding on the gears ------ed