ultimate five speed dog box - minispares (in part)

[guru_1071]

heres a few cheeky photos of a small project based on the minispares five speed box. basically, its a a hybrid of minispares five speed parts with new gears and shafts. virtually every bearing is new.

things to note are the pinion is part of the mainshaft, so no problems with it breaking between the base of the tooth and the spline which would hold it on in a std mainshaft

the drop gears are geared (1.21:1) to get the ideal ratios through the box and the correct final drive (19 teeth in the primary, to allow the final drive pinon to be a decent strong size)

the ratios are

1 - 2.093
2 - 1.493
3 - 1.197
4 - 1.1
5 - 0.889

this box is designed for the hardest possible use - no other five speed dog has been able to cope with the useage and power that this one should cope with - its expected to be able to run a true 200bhp plus and be useable with reliability on stage rally use - its sat under a kad 16 valver that has munched every other box that has been put under it.

this has been a massive project, about 18 months from the first conversation we had, even the small area I was involved in took weeks and weeks of pratting around .

it ran for the first time this weekend and reports are good







the cost?

well, if you need to know that, you cannot afford it!!! - it is huge!

[Richspec]

nice gearbox porn

[mini13]

What good is that...

It wont go in a remote box LOL

are those drops extra chunky?

[littler]

[pad4]

He He - can i send the pics of the drops to MINISPORT - might give em a clue to HOW THERE SUPPOSED TO BE MADE !!!!

[Smiffy]

Does this come with a special bell housing then ?

[sandman]

Where's the logic in making a dogbox with an overdrive??
This is beyond me... would have been miles better to have a 1:1 5th; better acceleration and a higher F/D ratio= stronger pinon.

[guru_1071]

Where's the logic in making a dogbox with an overdrive??
This is beyond me... would have been miles better to have a 1:1 5th; better acceleration and a higher F/D ratio= stronger pinon.

ed, in an ideal world it would have probably been done this way, but that would have required a complete new gearcase to allow space for the gears to fit - this was looked at but was mega money. this is before all the problems with moving the lsd around etc etc. this option was looked at first, but the price for a bespoke case forced the people spending the money/doing the designs to look at another way of doing it.

the other way would have been to have had the fifth as above (i.e the wrong side of the final drive) running a reduction gear to walk the final drive down to try and get some strength back into the root of the pinion - this has been done before, but again is very expensive and requires a lot of extra moving parts - the general opinion was also that whilst it looked good (and worked) on paper, in actual use it proved very difficult to get reliabilty.

the biggest improvement is the pinion been part of the mainshaft and the generally bigger mainshafts and bearings - in usage the size of the dogs / teeth etc dont really cause problems, it was the pinions breaking and punching through the case that caused most problems/expense when used with the kad type 5 speed dog box

lack of acceleration is not really a problem in the car this was designed for!, the most important thing for the user is the ratios spread so its pulling hard when he needs it to be.

[guru_1071]

Does this come with a special bell housing then ?

the standard one is used, it just need relieving a little

[sandman]

KAD's box got a 1:1 5th - dont it?

[Smiffy]

Yep like all true 5 speeds, only ever heard of 3 manufacturers ever making these. Colletti Francis, KAD and Hewland, think they all use special casings ???

[Michael7]

Jack Knight also made 5 speeds to fit in the remote gear case, and the case is basically standard.

I have one in USA and it has a few specifications that are similar to the Mini Spares one, such as the pinion gear is integral to the main shaft for some ratios.

You can see a few photos here, just scroll down to mid-page.
http://www.cardomain.com/ride/2534825/1966-austin-mini

[guru_1071]

KAD's box got a 1:1 5th - dont it?

yes, but one of the problems of the kad box is that it has a dog-leg first to accomodate this, with the rest in the gears been in a normal 'H' pattern.

the guy who has developed/paid for this kit used the kad boxes (and blew two up in a month due to the pinions breaking (not really a fault of the kad box, but it started him on the path of this creation) and said that one of the problems was that it was very easy, in the heat of competition, to forget where first was - it was also quite awkward having to go from 2nd into first (for hairpin bends etc) - using a change thats a standard 'H' with fifth in a more natural place is easier as your only going into top when the going is pretty good. - if it starts getting frantic 1/2 or 3/4 are just a back and forth movement.

he says that fifth been overdriven rather than a direct 1:1 is of no detriment whatsoever to either performance, use or design of the box.

[guru_1071]

Jack Knight also made 5 speeds to fit in the remote gear case, and the case is basically standard.

I have one in USA and it has a few specifications that are similar to the Mini Spares one, such as the pinion gear is integral to the main shaft for some ratios.

You can see a few photos here, just scroll down to mid-page.
http://www.cardomain.com/ride/2534825/1966-austin-mini

i doubt those JKD ones will be anywhere near as strong though, the mainshaft with the pinion attached isnt fully one piece.

just goes to show though, theres nothing ever new, just old ideas rehashed!