Straight cut gears

[crankedup]

I am considering the purchase of an vintage car (1929) which uses an straight cut gears in the box. Assuming the car has the grunt for towing, about one ton weight caravan, would the straight cut gears make any difference to towing as against the more usual gear road going gears pattern of cog cutting? Thanks

[dan19evans]

hmmm you could put more strain on the gears if towing something really heavy because straight cut gears arent as strong as helical gears, but i think you should be ok with a 1tonne caravan

you might have fun changing gears while towing though

[Auntieroll]

dan19evans said:

hmmm you could put more strain on the gears if towing something really heavy because straight cut gears arent as strong as helical gears, but i think you should be ok with a 1tonne caravan

you might have fun changing gears while towing though

What evidence do you have that straight cut gears are not as strong as helical cut gears? Noisier ,yes, less friction between the teeth,yes,but less strength,I think not.

[dan19evans]

Auntieroll said:

dan19evans said:

hmmm you could put more strain on the gears if towing something really heavy because straight cut gears arent as strong as helical gears, but i think you should be ok with a 1tonne caravan

you might have fun changing gears while towing though

What evidence do you have that straight cut gears are not as strong as helical cut gears? Noisier ,yes, less friction between the teeth,yes,but less strength,I think not.

because the teeth on helical gears are mounted diagonally, the teeth are longer and therefore have more surface area. because theres less surface area, there is therefore more strain on the gears

[camelotr]

If they are made of the same material/treated/hardened the same way, then straight cuts are definiatly weaker then helicals.

Sorry to ask this, but why towing with a prewar classic?...

Edited by camelotr on Sunday 20th June 22:07

[dan19evans]

camelotr said:

If they are made of the same material/treated/hardened the same way, then straight cuts are definiatly weaker then helicals.

exactly

camelotr said:

Sorry to ask this, but why towing with a prewar classic?...

i thought the same thing...

[dan19evans]

Weslake-Monza said:

So if helical gears are stronger why are all pure racing gearboxes using straight cut gears?

because straight cut gears give better power delivery

[stevieturbo]

And no thrust loadings on the gearsets/bearings I assume.

[camelotr]

Exactly

Competition parts supplyers compensate the weaker structure by using superior materials/hardenings.

[TheEnd]

Despite all that, it's pretty irrelevant whether they were straight or helical, as they would have been made to a certain strength by design anyway.
Helical would be made smaller for example, as they are stronger size for size.

It's like saying what is the more powerful engine, petrol or diesel, without any mention of the capacities.

Generally, all your super strong gearboxes are noise straight cuts ones, and you average car ones and nice and quiet helical cut.

[stevieturbo]

TheEnd said:

Despite all that, it's pretty irrelevant whether they were straight or helical, as they would have been made to a certain strength by design anyway.
Helical would be made smaller for example, as they are stronger size for size.

It's like saying what is the more powerful engine, petrol or diesel, without any mention of the capacities.

Generally, all your super strong gearboxes are noise straight cuts ones, and you average car ones and nice and quiet helical cut.

Gear width is limited by space within the box. And in most cases like for like, gear width rarely changes from helical to straight in any given gearbox. There simply isnt the room to make the gears wider.

The materials used do of course change though