Okay so in the planning and dreaming stages of my 1275 build.
It will be an A+.
Blah blah.

So drop gear, and idler gears.
Worth fitting straight cut items?
And if so, which ratio... 1:1?
What difference will the ratio make.
And what difference will straight cut vs helical cut make?

DR Mini, i'm looking at you


Thanks if anyone else can answer it, i'm not biased towards Dr Minis knowledge

Cheers.

Straight cut drop gears will be noisier but dont rob as much power as helical cut gears.

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Metal to burn, sparks to fly...

I already told you that i'm taking notes.... and that i'm not the only one doing it either

Honestly chief, its not worth it. If it WAS worth it, me and somebody else would already have a set ..... you should know that by now

You could supercharge for the same amount..... and actually increase your power with the investment.

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[NATHAN] -- Sold everything mini related and am back in big beautiful BMWs

If you're going racing and got the $$$ then yeah, good idea.
For the street, as said your money is better spent elsewhere on speed equipment that will add speed.
Too friggin' noisy for me....

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

I have a mate with straight cut drops on his Mini, they sound absolutely awesome! They are more efficient but not worth it for the $. I believe my mate had to buy new drop gears anyway (which are expensive) so he just bought the straight cut items. I'd love them for my car, but they would get a touch tiring after a while as they are a lot noisier than a straight cut gearbox.

And economy drop gears are probably not worth it, you may as well change diff ratio its probably cheaper. Another mate of mine has a 1275 with economy drops and 12" wheels and my 1098 could keep up! But on the highway he was almost off cam at 110
Anto.

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Technical Side Note For My Own Edification:
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Is part of the reason for going to straight cut gears to lessen the side load on bearings as the crank isn't trying to climb along the "helical-ly" bit of the gears?

Oh, and to add a bit of ricer-type zing-zing racer sounds at the stop lights?

I'm going to rejet the standard SU on the 850 to get a bit of poppy-overun bang bang sounds - now THAT will make it go faster surely?

you're so naughty cush

Straight cut are also a lot stronger & less prone to stripping in high torque applications due to the greater contact surface ("mesh") as compared to helical gears. Mini gearboxes are noisy enough as it is!

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Too many cars, and too little time.

Turbodave (a gear designer) debunked this one a year or two back on Mini classic and MiniMania forums.
Yes they reduce end thrust, but..
Actually they have less strength than helicals for a given tooth form- there is only 1 tooth in mesh at a time, so much more shock loading. This also flakes the hardening off the teeth, they don't last as long as helicals.
The way they are made is pretty agricultural too compared to BMC production gears.
BTW I used to make gears at the Railways Dept...

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Truly Doc?
There are a number of very reputable transmission specialists who use straight cut cogs to overcome such problems in a lot of other makes (wrx, skylines, etc).
Agreed there is no substitute for quality, and they will wear faster (and not be as tolerant of wear as a helical box) but wouldn't they be able to withstand a higher torque loading without stripping during their brief life?

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Too many cars, and too little time.

Quality wise I was talking about Mini drop gears nor Holinger etc which I agree are nice stuff.
IF you can fit straight cuts of larger diametral pitch (ie less teeth) than the helicals in- then yes they are stronger, at expense of way more noise etc. The point I'm making is, durability wise for a street car, they (hardening) won't last as long. Which I agree won't matter in a comp car.

re the helical drop gears though, the only real weak point is the idler bearings. One day I'd like a helical idler with Timken bearings in there..

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Those pages in my Vizard book are now stuck together - cos I LOVE the thought of that modification

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[NATHAN] -- Sold everything mini related and am back in big beautiful BMWs

justminis has one already.....

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

You still got the pic Kev, or want me to send it again?

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Steve

Fred Sayers confirmed this years back, straight cuts aren't as strong as helicals. For the reason already given by the good Doctor.

Having said that I have a set in the race car.