Jack Knight Twin Cam Heads

[Nathan1293]

I finally have some photos of the six speed box, it’s all stripped down for inspection. Fortunately it’s all good. Would you like me to post them here or in the technical area?

I also have the Jack Knight quick shift, which is quite different to the usual quick shifters.

[mk1]

Here would be goo, or feel free to start a new topic in the Tech section.

[Mini Mad Swede]

Wonder how many of the 6-speed they made?
As there's no class for competing with it, or there is?

[Nathan1293]

The gearbox as I collected it, dirty but all the important bits looked good.

[Nathan1293]

Same view but now clean and looking a little different.

[Nathan1293]

The holes in the right hand side of the gearbox bottom, in a triangle are for reverse gear in the five speed gearboxes. Five speeds have the 1st top left in the gate, to 5th top right and reverse is bottom right. The Mini Spares 5 speed appears similar, although I have never seen one of these in person.

The six speed box needs an additional gate as bottom right is sixth.

[Nathan1293]

You can see the main shaft here, with gears 1, 2, and 3. on the extended shaft the pinon gear then 6th gear, which then has a left hand thread nut fitted.

[Nathan1293]

Here you can see the Layshaft, it is a driven shaft unlike the standard 4 speed box, hence the splines on the shaft and the laygears.

I am waiting on some verniers to confirm the layshaft diameter, but I think it is larger than a standard four speed box.

[Nathan1293]

Sorry for the bad photos, I was trying to beat the rain and lack of sun light. I can take more if you want, I haven't cleaned the front plate with 5th attached as yet.

The first motion bearing and main bearings are the standard A+ size bearings. 5/6th selector is bolted to shaft in the bottom of the box and looks very much as though it is the same as 1/2 without the reverse gear cut.

[Nathan1293]

I also found this document recently on stripping and rebuilding a 5 speed box.

[Nathan1293]

The interesting thing is how rough the casting of the gearbox casing is, it has a distinctly rougher gain and more flash marks on the case than standard cases.

I have calculated the wheel speeds using the jkd 6 speed compared to other ratio sets, with a 3.9:1 final drive (that’s what’s it has), 1st is similar to 1st in a close ratio 4 speed gear set using a 3.44:1 final drive. Fifth is approximately the same as 4th in the close ratio 4 speed with the 3.44:1 final drive and of course 6th is a higher ratio.

So you get closer gear ratios with a wider overall spread, which isn’t surprising I know.

[mab01uk]

Many thanks for posting the detailed photos of the 6-speed!
Only ever seen one once on the JKD stand at a Mini show a few years back, as seen in my photos posted earlier in this thread.
It would also be interesting to see the Jack Knight quick shift sometime, if you have any pics.

I have had a Mini Spares 5-speed in my Mini for the past 20 years with no problems, although like most classic cars it has only covered a low annual mileage during that time.

[mk1]

Thanks for the great pictures!

That gearbox is a work of art! Shame the 6 speed never really got into real production.

[Nathan1293]

I believe this is a picture of a Tran-X 6 speed, which was the 6 speed gearbox used by the Rover works teams.

The main difference is 5th is 1:1. 6th being the only overdrive gear.

[Nathan1293]

Jack Knight quick shifter

Notice the modification to the remote, there is no going back to the standard shifter!

shifter_base1.jpg

The bottom of the gearstick and new piviot assembly. The gearstick is in two parts and inner and outer. The outer is tube that is should be set up to mechanically block reverse gear selection. I haven't included a picture, but there is an adjustable plate on the top, should allow the selection of forward gears and requires lifting the outer tube up to clear the plate to select reverse gear.

Shifter_stick1.jpg

A view inside the new mechanism. It all piviots on two bearings, and there is no slack here. You still have the slack in the rollpins connecting the remote rod the the gearbox. I haven't used it but it does feel very nice, hopefuly as nice a the old remote gearboxes!

Shifter_2.jpg

[BAD942B]

Looks like taper roller bearings in the top housing so no play there as there should be preload, could be a super slick shift if there is no play elsewhere

[mk1]

Typical original old school Jack Knight. Superbly "over" engineered regardless of cost.

Shame no one continued the business in the same manner.