6-speed UN1?

[Paul Thompson 'Hooligan']

Hi all -

Anyone fancy a 6-speed UN1?

Pic below shows a 'close ratio 6-speed dog gear' conversion that 'drops' into a standard UN1 Casing using a UN1 diff/pinion.

Torque capacity reportedly exceeds 'DOUBLE' the normal UN1 so might be of use to the more powerfull cars...

[Mark Worthington]

Wow - that's awesome. How much?

[Brian]

Now there's a piece of sweetness............

A bulletproof light weight six speed

[Mark Charlton]

Yes. How much? That looks awesome. Is it a one-off, or is someone going to give RBT some competition? [img]/ubbthreads/images/graemlins/blush.gif[/img]

[Chris Melia]

hi Paul

It would be incredible with a one piece input shaft to finish off the conversion.
Is there a reason that it has the standard style split shaft?

Regards

Chris.

[Paul Thompson 'Hooligan']

Hi all -

Thought that might get some interest! [img]/ubbthreads/images/graemlins/smile.gif[/img]

Chris - I suspect the conversion has a two piece shaft as it is available with either a standard renault spline, or a a standard 1"(23) Ford spline. By making it available with two (or more) versions of input shaft, the conversion becomes more compatible - I guess..

Also - looking at the joiner, it looks far more secure than the normal UN1/Renault item and primary input shaft does not neck down as small as the normal item.

Mark(s) - I'm jumping the gun a bit here - as it is featured in the Spring 2006 club magazine that will packed and posted tomorrow to members so I don't want to say too much yet, but, it is being produced in numbers and is comparable in cost to the well proven one piece shaft conversion that many of us (inc recently Howard Jones) use.

Not wanting to 'steal his thunder' - club member Julian Kingston-Smith (Jools) has one for his GTD and it is hoped to have a 'full hands on report' from him soon.

One of the features I like is the short path for the highest torque load (6th) - with 6th gear right up behind the pinion gear, just inside the geabox casing. The reverse idler fits in the rear cover section where 5th gear used to be. (presumably Renault stuck 5th there as it was cheaper to modify an existing 4-speed design that re-design the lot)

I am informed that the conversion has been designed by an F1 experinced engineer and IMHO looks great !!

Jool's please please tell all once you've driven it, providing you can wipe the wide grin off your face that I suspect your gonna have!! [img]/ubbthreads/images/graemlins/grin.gif[/img]

In the meantime - a view of the 'bits' is seen below.

[Eric A.]

How noisy will it be with the straight cut gears? Is this designed to be a more race oriented transaxle?

[Mark Worthington]

It'll be noisy - definitely a track-oriented gearbox.

Paul, regarding your comments on the location of 6th gear, I always thought that it was desireable to have first gear closest to the pinion gear because overall torque multiplication is greatest in first gear. Can you shed some light on this?

[Paul Thompson 'Hooligan']

Hi Mark -

I agree with the 'potential' for high torque with the multiplication factor as you put it in 1st gear but in my experience, high power high torque cars break traction all to easily in low gears BEFORE any real high torque is developed/applied. When we snapped the quill shaft on Roys GTD many years ago, we were hard on the throttle in 5th.

When I broke a drive shaft on the car at Gurston Down hill climb last year (the ONLY one we've ever broken) I was attempting to pull off in 2nd (as usual) but miss-slotted into 4th!! - as the clutch bit and I booted it - BANG!! the drive shaft snapped cleanly. In second, flooring it normally just smokes the tyres and in 3rd if track is damp..

So it is from this that I consider the torque actually built up to be highest in 5th. As I once said on a previous posting, if the gearing offered a 10:1 ratio (eg very small dia wheel), the engine will never work hard cos the wheels will break traction, whereas reversed, with very big diameter driving wheels, the load to the engine is higher as it will not break traction so easily.

Of course, that is only my understanding of it and I am not a qualified mechanical engineer (electronics being my background) so I could be talking a load of old Tosh! (again).

Perhaps any 'mechi techies' on the forum would like to explain the theory....

ps - as the designer is Ex F1 I presume he did it that way for a reason. If I am able to contact him, I will post what he has to say....

[Paul Thompson 'Hooligan']

[ QUOTE ]
Perhaps any 'mechi techies' on the forum would like to explain the theory....


[/ QUOTE ]

Any takers??? - i'm curious now too... [img]/ubbthreads/images/graemlins/confused.gif[/img]

[Howard Jones]

If I remember correctly the Renault way that the input shaft stub connected to the main shaft was left hand threads into a loosely pinned coller. This new six speed method looks like a splined shaft into a splined housing. Would this be better? I think so.

The pictures I've seen of broken UN1 input shafts all failed at the stress riser caused by the change in material diameter of the shaft itself. This was at a point right after the threads on the gearbox side of the shaft.

A similar sort of thing is at the same location on the "new" shaft right after the splines. The "new" shaft does looks the same diameter as the splines so maybe this isn't an issue as in the original Renault. This would be my bet of where a failure would occur if it did, never the less. I would have liked to see a one piece shaft. Now don't think I know enough about materials or gearbox design to have anything other than an opinion on this. I am only pointing out the little information I am aware of.

The fact is, the "new" stuff is nearly 30 years on in design, and taking into account for better materials and that the spline arrangement looks better than the threaded Renault method all may be well.

The other thing is the diameter of the shaft itself. I would assume that like other replacement/ upgrade shafts increasing the diameter would also make the "new" parts stronger as well.

Lastly I believe that straight cut gears are less stressful on the cases themselves than the original design. Straight cut gears have less of a tendency to force themselves apart under load. This produces less load on the bearings and their housings in the cases. The straight cut gears themselves do have higher stress loadings, stress risers at the gear face root, but can be accounted for in design.

The best part seams to be the full gear-set 1st-6th inside the cases with bearings on both ends and reverse hanging out back. This in itself would be worth the effort.

I think I agree with the idea that the location of the gears on the shaft in relation to the pinion gear being of the least important design points discussed here, although valid in concept.

I should say that I'm not trained in gearbox design. I have fixed a lot of bike gearboxes in my time thought so my opinion is worth what it cost.

Looks very interesting!

SO does anyone have a price? Gear ratios? Can a "kit" be bought?

[Malcolm]

So maybe at long last I get my spare gearbox back from Jools? Who knows? However Kevin has always said that whilst it is a dog box, it will be street driveable. Only one way to test that theory. Pull yer finger out, Jools!

[Joe T]

This is an interesting conversion very impressive, my comment on the stress aspect of this design would be helical gears spread the load into the endplates as well as the traditional forcing the box apart at the seams by trying to push the shaft backwards and forwards along there axis, straight cut gears tend to create the same force but shear loading the shaft bearings which is then fed into the casing.

Sometimes a steel cradle is used round the outside of a box to strengthen it if it was designed for a helical gearset and converted for straight cut.

[img]/ubbthreads/images/graemlins/beerchug.gif[/img]

[Graham Inchley]

Ratios anyone? Looks very interesting.

[Paul Thompson 'Hooligan']

Hi Graham

1st = 2.57
2nd = 1.84
3rd = 1.38
4th = 1.08
5th = 0.92
6th = 0.80

Final Drive = 3.44 or 3.89 or as already fitted to box.
[img]/ubbthreads/images/graemlins/beerchug.gif[/img]

[Julian West]

Looks really nice...!!!

as a comparison, could somebody remind me what the ratios are for the DB/quaife upgrade?

I've searched Dereks UN-1 website at http://www.un1.co.uk/ but can't find the upgraded ratios anywhere.

The stock un-1 013 ratios are listed as

1st 3.36
2nd 2.05
3rd 1.38
4th 1.03
5th 0.82

FD 3.44

[Paul Thompson 'Hooligan']

Hi Julian

Derek Bell Quaife Ratios as requested:

1st = 2.66
2nd = 1.75

3rd to 5th are as standard box...

[Graham Inchley]

Cheers Paul [img]/ubbthreads/images/graemlins/beerchug.gif[/img]

Revving to 6 gives good numbers. 1st might be a bit tall for the road though. I guess a quality clutch will help a lot here. Has anyone images of the gear change linkage for the UN-1? They would be very useful when fabricating the Southern GT.

[Howard Jones]

Um... I think that the ratios are as follows. Jack Night makes the D Bell set and Quaife makes the C Cole set.

1st 2nd 3rd 4th 5th

Renault standard 3.36 2.06 1.38 1.06 .82

D Bell 3.0 1.95 1.38 1.06 .82

Chris Cole 2.66 1.75 1.38 1.06 .82 (optional.75)


I am really sure about this. I have emails from all parties right in front of me. Dated Nov.- Dec. 05. Renault data from GTD manual

If they have changed since then I stand corrected.

By the way I have the C Cole set. 1st is fine on the street with a 3.44 final. 2nd is nice and close to 3rd. Feels like a nice CR 4 speed with a cruise 5th. This may make 2nd usable on track because the Renault 2nd was too low except for the very slow corners. None of the tracks out here on the west coast have a 1st gear corner.