Javelin/Jupiter gearbox

[Edmund Nankivell]

I would like to see the Jav/Jup gearbox redesigned with new innards so it works reliably, has good longevity, can be overhauled relatively easily, maybe uses metric bearings, so the future of these cars can be assured. Without a sensible gearbox, we may be consigning future generations to non-Jowett motoring. If we use a non-Jowett gearbox via adaptor(s) we need to be sure the gearbox is from a car that will live for ever, e.g. TR2.

[Jack]

Ed, would that mean a change from current (distinctive) column change to a gearstick through the floor?

Some of my recent thoughts have been around finding a good and simple replacement engine and gearbox for a Javelin and Jupiter (obviously if it fits one then it fits the other!) that is reliable, requires minimal modification of other parts, and is readily available on a very common and low value vehicle. Taking an engine and box from another vehicle might be more straightforward than trying to mate another gearbox to the existing engine perhaps?

This also gets around the tinkering that owners need to do in order to keep their cars running properly - a more modern engine and gearbox is a much lower maintenance proposition, it seems one of the major fears when discussing Jowetts with novices is the complexity and subtleties (and therefore cost) required when rebuilding the engine and gearbox for a restoration project. It might also present a replacement that can get a car on the road quickly, with minimal modifications, so that it does not sit in the garage waiting for an engine to complete the project, and the engine and gearbox can be rebuilt as an ongoing job while enjoying the look of the cars, if not all the engineering that went into them.

Jack.

[Edmund Nankivell]

No, I thought just the innards redesigned so the box works reliably in the long-term.
There are two Jupiters in France where what you are thinking of has been done. They have Alfa Romeo flat 4 engines, not sure about the gearboxes. One of them is undoubtedly fast - he sprints it. I am enough of a purist not to approve of this.

[Leo Bolter]

Gidday all.

Edmund wrote

I am enough of a purist not to approve of this.

I'm right with you on this Edmund . . . a Jowett with another gearbox is "bad" enough, but one with a different makers engine (and gearbox) is no longer a Jowett in my humble opinion. It's a "hybrid" . . bucket seats and shagpile carpet brings a car into this category too . I think I have seen a Bradford truck with a mahogany deck held down with brass screws . . . but maybe that was just in a nightmare!

Yes, it's hard to draw the line and it all comes down to a personal opinion, but certain mods (subtle and to modernise and update for safety, for instance) I personally think are okay. Things like turn indicators, heated rear windows and even radial tyres spring to mind.

And yes, my car does have things that it didn't have when it left the factory, but it's restoration was done with the thoughts of "originality" at the forefront of my endeavours and any changes were kept to the barest minimum where visible, and others "tucked away" where possible.

There! . . that should stir up some discussion . . .

Best regards to all.
Leo.

[David Kemp]

Three thoughts, one is that I thought people had fixed all the Jowett foibles, so just spend the time & money on a proper rebuild of the original parts.
Second with a unique car like a Jupiter, if you don't like the drivetrain, and love the Alfa drivetrain buy an Alfa! If you need to have Jowett style, build a replica. lastly this has been said before....if you replace the Jowett parts with something more modern, eventually these modern parts will also become just as scarce & fragile in the future.look at the Vanguard powered Jups...now converted back to Jowett, as the club has a good supply of Jowett parts & expertise. Having worked for Alfa I doubt you would get any more reliability out of Alfa used parts, alfa owners all seem to think they are formula one racers & thrash their cars badly,most aren't worth rebuilding(unlike a Jowett)

[PJGD]

Is the Jowett gearbox really any more fragile than the engine? I would say they are both marginal.

Nevertheless, there are more parts and options for keeping the engine going than is perhaps the case for the gearbox. No doubt the gearbox is a weak link and a more robust example would be a big improvement. However, I am very doubtful that we would find another gearbox innards that could be used within the Jowett gear case; gearbox designs are usually much more unique to the manufacturer even than engines are. I would have thought that asking someone like Dennis Sparrow who is exposed to the innards of various non-Jowett cars might be a good place to start?

Philip

[Forumadmin]

I have approached gear manufacturers at shows on two occasions and both would have no problem replicating and improving on the Jowett gears. After all, Jowett screwed up a perfectly decent Meadows box. I have raced and rallied one box for twenty years with no problem- except a synchro ball popping out on the way to Le Mans. Built properly they do last. Yes we do know the failure points and really only one remains to solve- the strength of 1st gear. The problem now is that most gears are worn so we do need to have new ones made. At the same time we could ask the experts what they might improve. We know from ex-Jowett employees that the main problem was lack of finishing to the gears(lapping), care in assembly as well as a worn and badly set up gear cutting machine. This machine caused the same problems in International Harvester that used it later.

Imperial bearings may not be a problem as they are still made for the US market.

[Jack]

One advantage to an engine and gearbox swap using an alternative and very common, more modern engine, is that you have the original Jowett item on the shelf, not wearing, and being preserved for the long term. An engine swap (if one chose the right engine) should not be a massive engineering feat, so it is not a one way decision that can never be reversed.

On the gearbox, if we could find a route to making a 5th gear available, either through re-engineering the gearbox completely, or finding an appropriate unit with integral overdrive, I think there would be quite a lot of people interested in such a thing, particularly if it retained the original look of the gearbox on the car - bolting on a gearbox from another vehicle using an adaptor plate strikes me as being a big step away from originality.

Jack.

[chapman]

I have currently experimented with mating a Ford 5speed gearbox onto the Jowett bell housing and with a thin aluminium plate this fits very easily.
The next task is to modify the output shaft as the ford one has three 'arms' whilst the jowett box has two to fit into the coupling.
It looks like the props haft will be a couple of inches too long but that is not a massive engineering problem and it also looks like the shaft bend is less than about ten degrees so it might work without too much wear.
If it does work gears one to four have exactly the same ratio as the jowett box with fifth being 0.8 ratio so it will be an excellent fifth gear or overdrive
The downside of course is that it is not Jowett and it is not column gear change and it would not be quick to restore it to standard
This method however is fully approved for the MGB which was also a bit low geared
On the LeMans rally we had quite a few problems with Jupiter overdrives and couplings and I believe that this could be an elegant solution for the non purists who just want reliability
I think that this Ford K series box was used in many models so they are still available
Tom Chapman

[PJGD]

Tom,

That is certainly an interesting and plausible modification. I will be interested to see some (uploaded) photos when available including the Ford gearbox alone sitting on the floor, the aluminium adapter plate, and then the installation. I will be interested to see how you manage the gear change.

Philip

[Edmund Nankivell]

I was surprised to read that at the Le Mans rally there were overdrive problems. Not with my Jupiter! Was this the 50/2000 Le Mans run?
I would pay good money towards a new set of gearbox innards that were reliable, long-lived, no jumping out of third, or first & reverse, no selecting two gears at once, and the teeth remain connected to the layshaft. This would, I think, ensure our cars wouldbe in running order for as long as classic cars are run and treasured.
A full gearbox swap would only be acceptable to me if from a comparable classic car, with the likelihood its parts would remain available. EG TR2, TR3 or such-like

[CyrilWhite]

The views regarding gearbox mods and replacements are always interesting ,a company called hi-gearengineering.co.uk
is located near me and judging by the no of MG's and TR's opting for 5 Speed Ford conversions ,it's not just a topic confined to Jowetts . The web site is interesting ,just Google hi-gear ,the company is a small one man and his dog operation ,run by a good Engineer and very knowledgeable . The column change ,more than the gearbox ,is I suspect the main objection to changing to what is arguably a better box that would help the engine to cope with modern road conditions .

[Forumadmin]

http://hi-gearengineering.co.uk/
Thanks Cyril.

[Brian Cole]

"Ed is right A car aint no good withouy a gearbox! But then it aint no good without an engine and if we dont get no crankcases we wont have no engines!"
And then, we will have to become Ford /Jowetts anyway. What happened to the new crankcases,? Without them we will eventually be stuffed!
Has anyone actually built up an engine with the new ones?
I would imagine that the main problem with obtaining new crankcases is the machining. If the club could invest in a CNC programme then we could have them made in batches to suit demand and presumably they would all be one hundred per cent accurate, better than the originals by improving the dodgy bits. I would imagine we now have a pattern, and castings are no problem. So what is stopping us?
The cost to the club for the machining programme could be recovered from purchasers in the unit price.

[Edmund Nankivell]

I think there are quite a number of crankcases about which are either usable as they are, or repairable.
I understand that the new cases made by the club are not accurately made and need quite a bit of line-boring to make them usable