25 replies to this topic

[fikus01]

u forgot to mention cheap drop gears usually clatter at tickover!! expensive jack knight ones i've heard dont tend to be so noisy!!

Edited by fikus01, 11 November 2006 - 01:35 PM.

[998dave]

u forgot to mention cheap drop gears usually clatter at tickover!! expensive jack knight ones i've heard dont tend to be so noisy!!

I didn't mention drop gears at all... I asnwere the question posed! :-P

Dog gears and Synchromesh have their own differences too though, which I think Fikus is highlighting, due to the manner in which they change gear. synchromesh have a couple of friction plates t equalise speed, similar to a clutch, before going into gear these wear evetually causing grinding on ger change.

Dog gears just jam in and out, quicker change with practice, but harder to perfect.

Dave

[fikus01]

it says difference between straight cut and normal gears!! and straight cut drops clatter!! only at tickover tho!! some worse than others

[998dave]

Okay, At a guess 'd say probably due to the problems with feeding them together, some being better machined with closer tolerances would be less likelt to clatter. Under power one would imagine that the load would push them together so less chance of clatter.

by the way. whats wrong with French cars? My ex had a Citroen AX, is was wonderful looked nasty, gutless, cheap, plasticy, handled like a pig, and fell apart like a hooker with a habit... Oka, I see your point! )

[Sprocket]

A full answer for once.

Manufacturers but helicoil gears in cars for a reason, and not because they've pretty or much more expensive to make, it's infact because you increase the contact area between each gear wheel and generally have three teeth 'meshing' at a time. This reduces load on any one tooth and makes for a mroe reliable and longer lasting gear set.

Straight cut gears do indeed reduce friction and side loading, and are more efficient, however they're not as reliable, long lasting, or quiet.

As an aside, most cars have straight cut reverse gears, which is what gives you that whining noise, and mini's (and metro's, etc), have straight cut first gears! Which is how you can tell it's a mini pulling away when you can't see it!

Hope that helps!

Dave )

now thats the perfect answer that could'nt of done better meself
Mick ...

Of course it's perfect, I'm a professional! :-P

Not so perfect Im afraid

Firstly, helical gears may have three or more teeth meshed, but, the contact patch on each tooth is small, the sum of the contact patch on helical set is probibly the same as that on a straight cut set. Dont forget that the helical cut teeth are not straight, thats down to the geomety so the contact patch actaly moves along the tooth as the gear rotate

Secondly, more importantly, and the main reason manufacturers choose helical cut over straight cut is there ability to reduce the noise levels.

[fikus01]

i was told once that jkd straight cut drop gears have a flat machined tooth head as oppose to a sharp one!! thast why they r quieter!! the others can bottom out causing more noise or summit!!

[Guess-Works.com]

as far as I'm aware all SC gears have flat topped teeth... and I've not noticed anything 'special' about JKD over tran-x or minispares

[fikus01]

hm, guess we'll never know unless we'll have them side by side!! only 1 of those wise man once told me things!!

[Guess-Works.com]

admittedly the gear profile is different, but that's no different to any gear manufacturer.. like minispares wont work (well not as designed) with Tran-X or JKD, they have to be the same set

[vasi]

Fikus, after my rattly drop post of recent, I'm thinking clattery straights is more a function of cam, as I have JK ones with a 286 scatter.

Although they were from minispeed so probabably stolen.

[fikus01]

yeh i keep forgetting these little things!! bin a while since i've spent some time round a decent a-series lump with straights!! lumpy tickover = clattering drops!! even with some helical cut ones!!