Dog box question - Involute Vs. Face Dog......
Turbo Mini Forums

Hi guys, just quick question in relation to dog boxes - i'm currently rebuilding my hillclimber & looking into going from s/cut synchro to a dog box. Which of the dog boxes is most suitable for a) ease of use & b) longevity between rebuilds - face type dog engagement (swifty/med etc..) or Involute boxes (JKD's)....?

I've driven face type dog boxes before in other cars so know the gearchange characteristics of those, did JKD involute boxes change similarly? Also the face dog boxes i drover were fitted into GpN rally cars and were getting rebuilt more frequently (obviously an amount due to their use).

So which of the boxes (assuming good driving.!) seem to have longer overall life? I'm not after a fit and forget, just an idea whether to go new with a swifty, or try and source a Jack knight.

Thanks guys...!

For every action there is an equal and opposite criticism.

Involute refers to the profile of the actual gear tooth if I am thinking straight.

Ahh with you, i was along the lines that the involute bit referred to the multiple engaging teeth on the dog gears.?

For every action there is an equal and opposite criticism.

I don't think it does. Involute is the form of the gear teeth as they mesh.

With you. I wonder if the different dog setup on the jack knights has different terms too.? That's the bit I'm interested in, the actual engaging part of the dog teeth in respect of wear and gear change.

For every action there is an equal and opposite criticism.

What Tom says is correct. In essence its a continually rolling contact point of the gear.

In terms of wear, iv`e not really seen any reports of the gear teeth them selves wearing out. Many reports of them being smashed to pieces.

Not in the dog boxes so much really.

http://en.wikipedia.org/wiki/Involute_gear

Thanks guys, brill animation Joe. That's a good bit of info. So yep it's just the dog engagement I'm trying to find out about, any comments about driving the jk boxes compared to swift or med dog..... And how well they both fair over time, on the dog teeth...

Nick.

For every action there is an equal and opposite criticism.

I think you the real question you have to ask is how easy/ difficult it is to get spares for the JKD box these days.

I see no comparisson between the Swiftune box and the JKD box. Two different animals if you ask me

Fair comment, i see how rare the jkd's are, let alone any bits. I've chance to look at both and just want to assess which will give better life (due to the dog engagement being so different in design) and ease of operation.

For every action there is an equal and opposite criticism.

I think you'll find that all SC boxes are involute, and jus t calling thenm involute was jsut a marketing ploy by JK,

Seems almost as though they are in constant mesh/contact much like helical gears, but without the side thrust/power loss? if so, are more boxes involute jus not named as such?

Yep thanks guys I think as you say a marketing ploy by jkd makes sense. So just any opinions would be a help as to longevity and driveability of both. Any of you guys driven both jk and face type boxes.?

For every action there is an equal and opposite criticism.

I think Joe is right, JKD just used the term 'Involute' more as a marketing angle to highlight the fact their gears were of a superior tooth geometry compared to early straight cut boxes which used simple tooth profiles, being easier to manufacture, but at the cost of durability and excess gear noise. The involute profile reduced both noise and wear rate.

Nowadays with modern transmission tooling, all staright cut gears are 'involute' with Quaife and Tranx likely to be the two main companies used in manufacture of the high end gear kits, I'm not so sure where Minispares get their gear kits manufactured nowadays, but at one point it was Tranx.

I wouldn't get hung on the 'Involute' bit as its probibly just a term these days.

Edited by Sprocket on 28th Sep, 2011.

Sure thing, the involute gearing makes perfect sense. What I'm angling at is any real world difference in driving or strength of either unit.?

I agree the dog principle is the same throughout, but the jkd being different in design to all the new stuff, multiple dog teeth with a selector that slots over the top, as opposed to lesser number face type dogs that engage face together (as the swifty). How does this translate to driving/gearchanging and wear over time.

For every action there is an equal and opposite criticism.

what sort of power are you planning on running to warrant the dog box?

one day boost will be mine!

Approx 140ish, hillclimb and sprint use.

For every action there is an equal and opposite criticism.

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Thanks Carl, just the answer I was looking for :) ultimately I want a box that, while still down to the skill to drive it, is as forgiving and slick as possible.

Nick.

For every action there is an equal and opposite criticism.

until this cam up tonight I always thought that involute refered to a reverse angle on the dog to hold it in gear

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