50 replies to this topic

[tiger99]

There are good reasons for thinking that helical gears are actually stronger than straight cut, as well as being quieter. The weak point is the bearings, because straight cuts impose hardly any load on the idler gear, whereas helicals try to make it twist sideways. The load on the primary gear is of little importance, as when power is being transmitted it is rotating with the crankshaft, which is rather substantial. Also, the gearbox input shaft runs in a ball race and a set of decent rollers.

Fix the idler gear bearings and you can have the best of both worlds, quietish gears and lots of power capability. I would suggest getting rid of the troublesome thrust washers and fitting bearings, such as taper rollers, which will resist end loadings, but to do it properly will involve modifying the gearbox and transfer casings. It would be necessary to bore through the transfer case, and fit a bearing adjuster which could be accessed with the flywheel removed, and a sealing device to cover it. I don't know that there is enough metal to do what I envisage, so a new casting, or maybe building up with weld and re-machining, would be needed.

Or, there is a better solution, chain drive, with no idler needed, and most importantly, less power loss! Maybe someone like Jack Knight would be able to make the necessary bits.

I think that some simpler idler bearing conversions have been attempted in the past, but don't know if they achieved their objective.

Noisy gears are really not an option in a car which is actually going to be used. Cooperman has explained some of the damage that will result to your hearing, but there is also the fatigue problem, which will severely limit how far you can drive it in one session. You really can use a quiet car much more than a noisy one, and surely one of the objectives of having a Mini is to be able to use it? For the same reason, excessively hard suspension, which does not in any case improve the road holding, is not a good thing either. Also think about comfy seats, decent heating and ventilation, etc. Such things all add up to getting more enjoyment from your Mini, not less.

[The Matt]

I think anyone considering buying straight cut gearsets and transfer gears should go out in a few cars that have them fitted.

If I compare my old 1380 to Bakker110's 1293 Clubby, the difference in noise is unreal. His have that LOUD straight cut whine that you can hear a mile off, yet mine were far quieter.

Some gears have the teeth tips 'topped' to reduce the noise generated by SC gearing and that makes a substantial difference I believe.

As I said earlier, the Trann-X ones weren't that noisy.

And yes, helical gears are theoretically stronger than SC ones. But SC ones have been proven to be strong enough for 200+bhp builds and are used to reduce side load on the transmission case.

[oltonlad]

"quote" Maybe someone like Jack Knight would be able to make the necessary bits.

 

 

i doubt it, they went bust ages ago.

 

 

 

[mini13]

[Artful Dodger]

 

 

what THE hell!

 

thats a crazy idea, 100s of horse power through a chain XD  

 

 

did it work?!?

[jaydee]

Nice chain!

I think SAABs were using a similar system..anyhow if it works for an R1 engine mini, surely will work in an A series

[Captain Mainwaring]

It works in my Pajero and that's putting 225HP and globs of torque through it - it's a bit wider than that....

For that matter my bonneville puts 50 BHP through a single morse chain (now converted to duplex)

Just needs something like a span box to keep a bit of tension on it and make sure the maximum chain velocity isn't exceeded with those sprockets.

[Artful Dodger]

what is the advantage though, the gears are fairly efficient (talking about SC) and dont take up much power to transfer the power from crank to primary shaft, you also cannot change ratios very easily at all with this, and there is a fear of the chain snapping. i only assume the gears would be stronger than the chain, but i dont know, never worked with chains!

[mini13]

That chain is actually something the BL competitons dept came up with in the 60's,

 

From the size of chain I cant imagine it wouldnt have been up to the job, but sadly I don't have any more info on it. perhaps they only came up with it right at the end of the mini's competiton like so it never got used?

 

as above chains like this are used for similar applications, for example IIRC they use one

to transfer drive to the front wheels on the Sierra XR4x4.

[mini13]

from what I have read chains are more efficient.... as there is little metal to sliding involved, the only sliding in between the pin and link (which can be made as a bearing on larger chains)

 

I belive this is the crux of why bicycle hub gears are not used for racing, there seems to be about a 2% difference in efficency

[Guess-Works.com]

I think the main problem is one of the gears is free floating and not fixed to the shaft, which will cause dreadful alignment problems with a chain. Secondly without a tensioner the chain would be flopping about all over the place unless really tight, and then if really tight or kept under tension there would be a tendency for the primary gear to bind on the crank...

 

You would need to redesign the primary gear and crank connection to run on something like loaded taper bearings ( like a wheel bearing ) as opposed to bushes.

Edited by Guess-Works.com, 27 May 2013 - 10:47 AM.

[Artful Dodger]

but what was the benifit? why go as far as to re design the teeth on the gears, there must have been a significant benifit to warrent this!

[mini13]

Good point on the alignment, that could kill a chain pretty quick, mind you the primary only wanders because its helical, the SC ones seem to stay put wear wise.

[E.L.M.O]

I've got a whole Jonspeed gearbox with straight cut transfer gears for sale.

[The Principal]

I'm running these med roller bearing drops http://www.med-engin...set-roller-type

 

with a sccr box not that loud, word of advice though the top hat in the tranny case needs to be pressed in