Idler gear bearings

[DougR]

Hi folks, I'm wondering if anyone has come across a bearing upgrade for the helical idler gear? I fitted the S/C timken setup to a mk2 S and it was great apart from the noise. It would be great to have a similar bearing upgrade for the helical setup. Any ideas ? Thanks, Doug.

[Stoneface]

It has been done but there are no commercially available solutions I know of.
This might be of interest https://www.theminiforum.co.uk/forums/t ... rop-gears/

[Spider]

I have done a few, as Stoneface linked up above, but I've only been able to do them with A+ gearcases in a way that's 100% reversible and doesn't involve any machining of the gearbox case and flywheel housing. This is due to the bearings used and to get at least the same bearing rating as the A+ Idler Gear Bearings and even then, these use a custom bearing, not a way I wanted to go, but it took me several years to get them to this point.





I went this way mainly to get around the side thrust issues and how, in particular on A+ drop gears, the thrusts have little surface area and eat in to the casings. The other issue this helps with is correcting the misalignment between the flywheel housing and gearbox case, which causes premature wear of the shaft on the idler gear, it's teeth and the bearings, though, I have been aligning / matching cases and housing the past few years and found that goes a long way to getting these to last much longer.

[DougR]

Thanks lads. All very interesting. I'm building a pre A+ engine. I have a very good friend machinist. I might buy a Timken s/c gear and bring it and the helical one to him and ask "can you make that look like that?" It might put some pressure on our friendship. Cheers, Doug.

[Costafortune]

Tbh, I'd be line boring the gearbox and clutch housing to use A+ drop gears. I've never heard of one failing. You just fit these and you're done - no reason to ever go back to the skinny original bearings.

[cmiller]

I am going back in time here. I raced in the SCCA in the states in the 70's and when the straight cut taper roller idler gear first became available from Jack knight it was thought to be the answer of all idler gear problems. That proved to be true. After development Jack Knight came out with a helical cut idler gear with the same taper bearings. A friend ordered two for his use for street application. Time goes by and tries to order a couple more. Jack Knight replied that they were no longer being supplied due to a major problem. Taper roller bearings work perfectly on gears that are straight cut as many racers found out. The problem was that helical cut gears could not take the side loading on the bearings and failed in a short time. I still have one in my "history bin" of parts. Just saying.

Chris Miller

[DougR]

Right..@cmiller thanks for clarifying that it had been tried and it failed. The thought had crossed my mind. @costafortune that seems the best way to go. Thank you all for your inputs. Cheers, Doug.

[Spider]

The problem was that helical cut gears could not take the side loading on the bearings and failed in a short time. I still have one in my "history bin" of parts. Just saying.

Chris Miller

Hope the hand is coming good there Chris.

And that's why it took me years and I can only do them with the A+ Drops, the bearings I landed with need all that space. It's not easy to put in to words but part of the bearing assembly protrudes from either side of the gear and ends up 'inside' the bores for the original (A+) Idler Gear Bearings. The conversions I've done only have ever so slightly better bearings than the factory set up, but their biggest advantage is the bearing assemble doesn't care about case misalignment and there's no rotating thrusts to eat their way through the flywheel housing.

[Stoneface]

I still have one in my "history bin" of parts. Just saying.

Chris Miller

Hi Chris,
I would be interested to see this. I don't suppose you can add a photo of it and also the details of the bearings used?
Just because it wasn't possible many years ago doesn't mean it can't be done now, but it would be nice to know what was done previously.
Thanks.

[cmiller]

Sorry Stoneface. Like more than a few of "senior" forum members I am inept at such things. I never adapted to the technology of today. At times it frustrates the hell out of me but it is just the way my brain in wired.

Chris Miller

[TECH396]

Sorry Stoneface. Like more than a few of "senior" forum members I am inept at such things. I never adapted to the technology of today. At times it frustrates the hell out of me but it is just the way my brain in wired.

Chris Miller

Send me a picture via email Chris. I'll post it here for you.

[Spider]

Tbh, I'd be line boring the gearbox and clutch housing to use A+ drop gears. I've never heard of one failing. You just fit these and you're done - no reason to ever go back to the skinny original bearings.

I haven't had the time to look at the early flywheel housings but do they have enough meat in them for this ?

[BAD942B]

Tbh, I'd be line boring the gearbox and clutch housing to use A+ drop gears. I've never heard of one failing. You just fit these and you're done - no reason to ever go back to the skinny original bearings.

I haven't had the time to look at the early flywheel housings but do they have enough meat in them for this ?

Had quick look now at the gearbox & end case & I don't think there is