Starter motor puzzle

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Hi,

Helping a mate today with his 3a.

He has recently been having problems with the starter motor, this starter has been on the car for numerous years. He has owned it for 30+ years and has not changed it.

It is fitted with a bomb type starter. So got a WOSP replacement for this type of starter.

Fitted the WOSP starter (which was great fun  ), and had problems.

After lots of head scratching and removing the new starter we discovered this was the wrong starter. He commission number is TS59xxx and the ring gear has bolts.

So it would seem that the early starter motor has been fitted to a later engine.

Should have checked first and not assumed the correct starter was fitted.

Anybody come across this before, and i guess the bomb type is compatible with the later ring gear.

Thanks

Dave 

 

[Lebro]

Bomb type has 9 teeth on the bendix, which it throws into the ring gear from the front side, & is intended for the shrink on ring gear fitted to 2's & early 3's.

A 3A should have the bolt on ring gear, which uses a different original motor having 10 teeth on the bendix, & it pulls into the ring gear from the rear.

WOSP motors are available to suit both types - they just have a different no of teeth.

Bob.

 

Edited April 25, 2019 by Lebro

[cookie]

18 minutes ago, Lebro said:

Bomb type has 9 teeth on the bendix, which it throws into the ring gear from the front side, & is intended for the shrink on ring gear fitted to 2's & early 3's.

A 3A should have the bolt on ring gear, which uses a different original motor having 10 teeth on the bendix, & it pulls into the ring gear from the rear.

WOSP motors are available to suit both types - they just have a different no of teeth.

Bob.

 

Thanks,

Will count the teeth on the old starter.

What i don't currently get is how a bomb type was working on a 3a with bolt on ring gear.

Dave

[Lebro]

It will fit, but the teeth won't fully engage, I would have thought it was noisy when cranking.

Another thought is that I think I have read somewhere that a TR5 bolt on ring gear will fit a 3A, & gives the correct diameter for a bomb (9 tooth) to work.

Not at all sure of this last point, but someone else may know on here.

Bob.

[iain]

10 hours ago, Lebro said:

Bomb type has 9 teeth on the bendix, which it throws into the ring gear from the front side, & is intended for the shrink on ring gear fitted to 2's & early 3's.

A 3A should have the bolt on ring gear, which uses a different original motor having 10 teeth on the bendix, & it pulls into the ring gear from the rear.

WOSP motors are available to suit both types - they just have a different no of teeth.

Bob.

 

I think early 3As had shrunk on ring gear as well. Certainly mine does and it’s is the original lighter flywheel (22 lb) 

Iain

[Lebro]

7 minutes ago, iain said:

I think early 3As had shrunk on ring gear as well. Certainly mine does and it’s is the original lighter flywheel (22 lb) 

Iain

Quite possibly, but the point is that the two types require a different size gear on the starter.

Bob

[BlueTR3A-5EKT]

Ring gear interchanges.

The bolt on ring gear used in later TR3A, all TR4, and & TR4A, is unique in both tooth count and method of attachment, and to my knowledge there is no replacement/alternative. (at this points someone says - what about Daimler or Land Rover as they used the same starter bendix gear tooth count...You know what I never checked.)

The shrink on ring gear used on TR2-3 & some TR3A is unique in its tooth count and must be run with the correct bomb starter.  The diameter area on the flywheel that this ring gear mounts to is the same as the TR250/5/6/Spitfire/GT6/Vanguard.  This means the TR250/5/6 shrink on ring gear may be fitted to a TR2-3-3A shrink on type flywheel.  It will of course need to be driven by the appropriate matching starter motor from the TR250/5/6/Spitfire/GT6/Vanguard.

Before the arrival of the geared high torque starters, the use of TR250/5/6 ring gear on TR2/3/3A flywheels was in vogue by the racers who wanted more starter ummphh (due to tooth count ratios of starter and ring gear?) for their high compression engines, and more space in the engine to chassis area due to bunch of banana exhausts manifolds.  The pre engage starter of TR5/6 was deemed to be more powerful and reliable than the old bomb design, physically not as long & perhaps a bit lighter. 

Cheers

Peter W

Edited April 26, 2019 by BlueTR3A-5EKT

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Have checked both the old starter and new one both have 9 teeth.

The car has bolt on ring gear so should have a starter with 10 teeth.

Attached is a picture of the old starter with knackered teeth.

Any ideas how the old starter worked for many many years without causing problems till very recently.

Dave

[Lebro]

Actually does not look that bad to me. the front end of the teeth always get a battering as they are thrown (spinning) into the ring gear.

Bob

[cookie]

11 hours ago, Lebro said:

Actually does not look that bad to me. the front end of the teeth always get a battering as they are thrown (spinning) into the ring gear.

Bob

Hi Bob,

Guess you are correct the teeth are not perhaps too bad.

Just leaves the issue of how an older Bomb type starter works on a later 3A engine with bolt on ring gear.

Really need to solve this somehow as need to get the correct WOSP replacement.

Thanks

Dave

[RogerH]

Hi Dave,

is it possible to get at the ring gear teeth and measure the peak to peak distance. Cover a great an area as possible.

This should tie up with the peak to peak on the starter motor.

Roger

[Fireman049]

Dave ~

If you inform the TR spares supplier of the type of flywheel ring gear you have they will supply the correct starter motor.

This was my case when I purchased a high inertia starter motor from TR Bitz for my 3A (with bolt on ring gear).

Tom.

[cookie]

1 minute ago, Fireman049 said:

Dave ~

If you inform the TR spares supplier of the type of flywheel ring gear you have they will supply the correct starter motor.

This was my case when I purchased a high inertia starter motor from TR Bitz for my 3A (with bolt on ring gear).

Tom.

Hi Tom,

That is the issue we have. We told them we have a Bomb Type so a suitable replacement was supplied for this starter.

We have now found out the ring gear is bolt on.

So should we have a replacement for the starter (older type) or a replacement for the ring gear (newer type)

If the old starter was the wrong type i don't get how it has worked well for years.

Currently totally confused.

Dave

 

[cookie]

1 hour ago, RogerH said:

Hi Dave,

is it possible to get at the ring gear teeth and measure the peak to peak distance. Cover a great an area as possible.

This should tie up with the peak to peak on the starter motor.

Roger

Thanks Roger, may have to try this.

Dave

[Lebro]

5 minutes ago, cookie said:

Hi Tom,

That is the issue we have. We told them we have a Bomb Type so a suitable replacement was supplied for this starter.

We have now found out the ring gear is bolt on.

So should we have a replacement for the starter (older type) or a replacement for the ring gear (newer type)

If the old starter was the wrong type i don't get how it has worked well for years.

Currently totally confused.

Dave

 

I expect the 9 tooth starter will work with the bolt on ring gear, it just won't be fully engaged. Also, have a close look at the mounting holes on the bomb starter - have they been enlarged, or stretched towards the side away from the engine ? If so then the motor could be pushed further into mesh with the ring gear.

In The 1970's I did the opposite to this, & fitted a later (TR4) starter motor to my '3 with shrink on ring gear. I made it work by slotting one of the mounting holes so the motor could swing away from the engine a small amount to allow good meshing of the gears.  It worked well !

Bob.

[Fireman049]

Hi Dave ~

The starter should be matched to the bolt-on ring gear.

Tom.

[BlueTR3A-5EKT]

Just to be sure here. 

You can definitely see the hexagon heads of the bolts that hold the ring gear in place through the hole where the starter fits (or at least one bolt hex when the flywheel is in the right position) - Yes?   -  You are not just feeling the heads of the bolts that attach the clutch cover to the flywheel by poking your finger in around the flywheel.

In which case I would order a starter suitable for bolt on ring gear.

My concern would be the state of the ring gear teeth after a bendix mismatch. 

 

The bendix gear of the bomb starter as Bob has stated has  9 teeth the gear of the later stater has 10 teeth.  Photo comparison of these two bendix end to end.  9 tooth one is smaller overall diameter than 10 tooth. (I have a pile of new and used Lucas starter spares.  I do not have any rubber drives now.)

Just to tease is a photo of 3 bendix gears. 

• The one in the middle is genuine NOS 9 tooth TR2-3 bomb starter bendix gear.
• The one on the left is a 9 tooth that fits a bomb starter and runs with a TR250/5/6 ring gear,. Note it is a smaller diameter gear than the genuine TR2-3. 
• The one on the right is a 10 tooth gear for the later starter that works with the bolt on ring gear (This is in fact a Land Rover item & only needs part of the teeth machining away to make it 100% suitable for TR3A-4-4A - due to clearance in the bell housing)

Cheers

Peter W

 

 

Edited October 25, 2019 by BlueTR3A-5EKT

[cookie]

Hi Peter,

Here is a picture of the ring gear.

So l looks like its definitely bolt on and the teeth are not too bad (sorry about pic quality).

As mentioned this starter has been on the car since my mate obtained it 30+ years ago.

God knows how but it has worked fine for all these years and not caused too much damage. I wonder who and why it was put on all those years ago.

Guess we are going to have to change the WOSP 9 tooth one for a correct 10 tooth.

Dave

 

[RogerH]

Measure the teeth spacing first 

 

Roger

[cookie]

59 minutes ago, RogerH said:

Measure the teeth spacing first 

 

Roger

Thanks Roger, Will try that before changing anything. Although, as you know, its a right pain to get at.

Dave

 

 

[RogerH]

Take a mould with plasterceine covering three or more teeth

 

Roger

Edited April 28, 2019 by RogerH

[Motorsport Mickey]

11 minutes ago, RogerH said:

Take a mould with plasterceine covering three or more teeth

 

Roger

That's what Ken Dodd did !

Mick Richards

[RogerH]

Just now, Motorsport Mickey said:

That's what Ken Dodd did !

Mick Richards

was there ever enough plasterceine !!!!

 

Roger

[Fireman049]

Is that what Ken Dodd diddy?

Tom.   

Edited April 28, 2019 by Fireman049

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On 4/28/2019 at 6:26 PM, RogerH said:

Take a mould with plasterceine covering three or more teeth

 

Roger

 

On 4/27/2019 at 11:31 AM, BlueTR3A-5EKT said:

Just to be sure here. 

You can definitely see the hexagon heads of the bolts that hold the ring gear in place through the hole where the starter fits (or at least one bolt hex when the flywheel is in the right position) - Yes?   -  You are not just feeling the heads of the bolts that attach the clutch cover to the flywheel by poking your finger in around the flywheel.

In which case I would order a starter suitable for bolt on ring gear.

My concern would be the state of the ring gear teeth after a bendix mismatch. 

 

The bendix gear of the bomb starter as Bob has stated has  9 teeth the gear of the later stater has 10 teeth.  Photo comparison of these two bendix end to end.  9 tooth one is smaller overall diameter than 10 tooth. (I have a pile of new and used Lucas starter spares.  I do not have any rubber drives now.)

Just to tease is a photo of 3 bendix gears. 

• The one in the middle is genuine NOS 9 tooth TR2-3 bomb starter bendix gear.
• The one on the left is a 9 tooth that fits a bomb starter and runs with a TR250/5/6 ring gear,. Note it is a smaller diameter gear than the genuine TR2-3. 
• The one on the right is a 10 tooth gear for the later starter that works with the bolt on ring gear (This is in fact a Land Rover item & only needs part of the teeth machining away to make it 100% suitable for TR3A-4-4A - due to clearance in the bell housing)

Cheers

Peter W

 

 

Hi Roger,

Have taken a mould, the tooth gap on the ring gear is around 9mm. The tooth gap on the old and new starter is around 12mm.

Hi Peter,

As can been seen i my previous picture the ring gear is bolt on and the old starter looks like the one in your middle picture.

 

So i think I'm am safe in saying that the wrong starter has been fitted to this TR3a for many years and we have got the wrong WOSP replacement.

I would have thought that the ring gear and starter would have suffered far more than they have, thankfully they haven't. 

Back to the TR Shop to exchange the new starter for the correct one.

Hope you agree.

Thanks for all the help.

Dave