Lotus Elan

Ring Gear orientation

PostPost by: gearbox » Mon Aug 01, 2016 6:50 pm

Hi All;

Going through a 1970 Plus 2, I think it is an early 69 build. PO had disconnected every electrical wire and component on the car for some unknown reason, so I started to patch it back together. The first job was to reconnect the starter solenoid and see if the motor cranks. I found a gear reduction starter in the trunk and installed it back in place. The car cranked and then stopped. All I could hear was the starter spinning, but no crank. Removed the starter and had a new gear reduction starter on the shelf and installed that to the same result. If I manually crank the motor a quarter turn, it will grab and turn the motor, but soon as it gets to that one spot, it free spins, so it much be a bad ring gear.

Took the starter out again and examined the ring gear. Some wear, not terrible, but you can see the tips worn down. Not sure if this would of prevented the starter from not engaging at all, but empirically, it has to be the problem. So ordered a new ring gear and see that the gears are beveled on the front and back, but only on one side. So if you are looking at the flywheel from the back clutch side, the ring gear could be mounted with the bevels facing to the left or right. The original ring gear on the car looks like the bevels are on the right looking at it from the back of the clutch side, but this PO had installed the engine mounts upside down and shimmed it with washers, so everything on the car is suspect to me. So the question is, should the bevels be to the left or right looking at it from the back of the motor? Or does it matter? The gear reduction starter is wired where the motor starts spinning at the same time the solenoid engages the gear, so the bevels helps with the engagement. So just thinking it through, the engine turns counter clockwise looking from the back of the motor, the starter spins clockwise, so logic dictates the bevels should be facing right yes? Let me know if anyone knows for sure, Thanks Allan

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PostPost by: dougal9887 » Mon Aug 01, 2016 7:29 pm

Ring gear bevel faces pinion bevel.
lotus-twincam-f39/ring-gear-help-t34489.html#p234140
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PostPost by: gearbox » Mon Aug 01, 2016 8:06 pm

dougal9887 wrote:Ring gear bevel faces pinion bevel.
lotus-twincam-f39/ring-gear-help-t34489.html#p234140
Dougal.


Ok, that sounds logical and falls in line with my thinking that the bevels should be facing right looking at it from the back. Good thing I asked, Thanks for the quick reply Allan
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PostPost by: prezoom » Tue Aug 02, 2016 12:57 am

The ring gear I recently purchased from Dave Bean is constructed so as a pre-engaged or inertia starter will work no matter which way you install the gear. Makes things simple.
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PostPost by: rgh0 » Tue Aug 02, 2016 10:43 am

The throw on some pre- engage starters that people supply is incorrect and they dont fully engage the ring gear teeth. With a little tooth wear or maybe run out in the ring gear on the flywheel they will fail to engage. So check how deep the starter is engaging.

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PostPost by: gus » Tue Aug 02, 2016 12:55 pm

A gear reduction starter does not particularly care if there are bevels on the flywheel or not. The inertial starter needs them to engage

The dead spot in the ring gear implies that the car has or had a dead cylinder, causing it to stop in the same spot, so I would check into that.
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PostPost by: gus » Tue Aug 02, 2016 12:57 pm

Oh, and the way the starter is wired does not affect its operation. The motor cannot be enabled until the pinion is fully extended, it is the way they are built.
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PostPost by: gearbox » Tue Aug 02, 2016 1:40 pm

gus wrote:The dead spot in the ring gear implies that the car has or had a dead cylinder, causing it to stop in the same spot, so I would check into that.


Dead cylinder? Wow, that is the first time I heard that connection. Normally it's an incorrect starter alignment, poor engagement, bad starter, etc. But good to know. Don't know the history of the car, so not sure if the PO kept on driving the car with a dead cylinder. But another "while I'm in there" jobs to do. The fun just never stops lol. Thanks Allan
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PostPost by: gearbox » Wed Aug 03, 2016 11:18 pm

OK, throwing a monkey wrench into the mix. I had several flywheels in the basement from various Lotus Europas and Elans and they all had the bevels facing left which is opposite what I thought was correct. I brought the flywheel and ring gear down to my machine shop and had long deliberation with the shop owner and several of his machinists. Given the number of flywheels I had, some of which was original to the cars they came out of, and mostly late 60's and early 70's TC cars, we came to an agreement that the bevels on the starter helps engagement on the one side, and the bevels on the ring gear helps on the other. So basically, no matter where the flywheel lands, one of the bevels would let the gears mesh easier. Well that is the theory anyway. I decided to go left and see what happens and hope that it really doesn't matter and I'm just overthinking this whole thing. I'll let you know if something blows up lol. Thanks Allan
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PostPost by: DuncanC » Thu Aug 04, 2016 12:04 am

Any chance you have a diameter/number of teeth mismatch? Dave Bean's catalog lists many tooth counts for flywheel ring gears, suggesting they could have different diameters -- each would need the correct starter bendix.
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PostPost by: gearbox » Thu Aug 04, 2016 12:38 am

I noticed those listings as well, and from the 12 Lotus I had owned and the 4 I have now, they are all 110 teeth with a ID of 10.048" to 10.055". The ID of 10.167", 110 teeth, are the ones I use for my Formula Fords, or Kent crossflow motors, so don't know if any of these flywheels made it into Lotus production at the end of production in the mid 70's. The 132 teeth ring gears are from the 2.0 liter OHC that we use in F2000 and S2000. Again, no clue if this was in production or someone finding it better or cheaper to use. I also just looked at all my old Lucas starters and my new gear reduction starters and they all have 9 teeth. I don't have any 2.0 engines apart right now, but understand that they use a 10 tooth starter. Still not sure if it matters which way the bevels go, but I chose to go with all the flywheels I have found, to the left. Thanks Allan
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PostPost by: l10tus » Tue Apr 21, 2020 12:47 pm

The OEM starter enters the ring gear from the opposite side, compared to a newer gear reduction starter, so the majority of original ring gears fitted, are not correct for the replacement gear reduction starters to operate correctly.

The ring gear should be similar to those supplied by DB (with double champher) or (if it's "a single sided" champher type ring) - turned around on the flywheel.

Really, in order to fit a new gear reduction starter correctly, the ring gear on the flywheel should be replaced and turned around - or you are really likely to encounter inconsistant reliability in starting.

As mentioned in the earlier post, the gear reduction starter relies on the full engagement of its pinion gear being made, before the turning action is allowed to commence. If the pinion does not engage into the ring gear fully and is baulked by hitting an un-champhered gear, it will not start the engine.
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PostPost by: 2cams70 » Tue Apr 21, 2020 2:31 pm

gearbox wrote:OK, throwing a monkey wrench into the mix. I had several flywheels in the basement from various Lotus Europas and Elans and they all had the bevels facing left which is opposite what I thought was correct.


I was at the wreckers the other day looking for a starter from a late 90's Toyota Camry because they use the same Denso starter (with the exception of the drive componentry) that is used as the basis of many of the replacement "high torque" pre-engaged starters you buy these days. I managed to buy a used "high torque" pre-engaged starter quite cheaply to suit my Escort Twin Cam and was after a few spare parts for it.

I too pondered the question regarding which side the bevel on the gears should face. When I removed the starter from the Toyota Camry in the wreckers I took a few pictures and confirmed like you did that the orientation was not what you would expect. See attached pictures of the Toyota Camry starter pinion and ring gear
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This picture is correct orientation
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