9 replies to this topic

[robj2502]

Hi guys

does anyone know the difference between an involute dog box and a dog box or are they one and the same. Also if there are differences whats the advantages-disadvantages of both

cheers everyone and happy crimbo

[mini93]

these the ones from jack knight your talking about?? i think its just there name...but i do have one

[Dan]

I believe it's a fairly minor detail in the shape of the actual drive dogs that engage the gears but has a great effect. Involute is a geometric term describing a type of curve, involute sets have curved lozenge shaped drive dogs around the gear face whereas other designs have chunkier wedge shaped dogs. The involute dogs are a tapering curve which makes them engage easily as they pass each other and then lock firm as they take up drive. The conventional dogs are essentially just flat faced and smash into each other. I guess this means the involute mesh should last longer as well as being easier to engage but it really is just a guess. It's definitely not just a trade name though, there is a difference.

[icklemini]

Dan has it!

[mini93]

maybe thats why when i had never driven with a dogbox before found it easy to pick up
apart from clutch needs adjusting grr

[robj2502]

I believe it's a fairly minor detail in the shape of the actual drive dogs that engage the gears but has a great effect. Involute is a geometric term describing a type of curve, involute sets have curved lozenge shaped drive dogs around the gear face whereas other designs have chunkier wedge shaped dogs. The involute dogs are a tapering curve which makes them engage easily as they pass each other and then lock firm as they take up drive. The conventional dogs are essentially just flat faced and smash into each other. I guess this means the involute mesh should last longer as well as being easier to engage but it really is just a guess. It's definitely not just a trade name though, there is a difference.

Thanks very much Dan. awesome description looks like Involute dog box it is

[robj2502]

these the ones from jack knight your talking about?? i think its just there name...but i do have one

Yes it was the gearsets from jack knight that got me thinking about the question as others just call theres a dog box where jack knight make a point of including the involute bit.
How have you got on with yours? is it a 4 speed? as I have been looking at the new 5 speed guess they would be simalar but just with an extra gear

[mini93]

the 5speed ones are still through drive (1:1 ratio) in 5th anyway. Remember the gear which is through drive just locks the input and output shaft together so no whining noise will be heared
the thing that it does is brings the gear drop ratio closer so when you drop gear going into a corner you have the engine speed right to power out the corner

mines 4 speed, between gears theres about a 500rpm difference you can hardly notice it especialy changing high in the rev range going 3rd to 4th it basicly sounds as though im changing into same gear lol

1st gear is quite tall in the 4 speed one, i guess it would drop a little bit, but about 4,500 rpm in 1st with my 3.77:1 diff is 30mph in 3rd gear 30's 2500rpm

iv found dispite not driving with a dogbox before its been easy to pick up but as i also said earlier my clutch needs adjusting so it is crunchie at the moment, sounds baaaaaad
also aparently when using a weber carburettor, because you have to heel and toe (tapping the accelerator to bring the revs up on down shifts) it tends to twist the throttle spindle which as a result keeps the throttle butterfly partly open so my car now like to idle at over 2k revs

people always stair when i drive through town or somthing lol tis goooooood

[Jammy]

the 5speed ones are still through drive (1:1 ratio) in 5th anyway.

Not all of them, I think the KAD and JK are the only ones without an over drive 5th.

[mini93]

oh right, i knew theres been ones which are over drive but wasnt sure if were being produced now, also been told that 5th put alot of strain on the layshaft or other components and so shouldnt be used for acceleration and just for the rev drop to give better motorway crusing