Disc Brakes for Javelin/Jupiter?

[Jack]

All,

New topic opened to avoid getting too far away from topic on the Alloy Wheels thread.

Does anyone have any suggested cars using similar setup to the Javelin or Jupiter which had disc brakes fitted at the front?

There seem to be a couple of cars where this has been done, if anyone has details please pitch in so that I can investigate.

Hopefully we should be able to put together something that will make the conversion possible, and if so I will record all the parts required and get the necessary changes required to be able to do such a thing.

From Scott's comment on the other thread, it seems to be a standard Morris Taper fitting, so should be possible, but potential sources much appreciated so I don't have to spend weeks in the scrapyards testing things out.

Thanks in advance,

Jack.

[Chris Spencer]

Jack - If it's a standard Morris taper - I think you will find that this will cover much of the Austin / Morris range / family they baiscly upgraded the parts / fittings through the years rather than start with a whole new design - if this is the case I bet that the MGB front disc set up is not going to be that far away and would be my first port of call - more to the point all the parts are available as new items at reasonable prices.

[Srenner]

Okay, I have to correct an error on my part. I wrote "Morris" taper when I should have written "Morse" taper.
This is a standardized system of the machine trade to ensure uniformity, just like screw threads.

The point I was trying to make was the rear axle shaft taper is a common one to many cars, not specific to Jowett. The front stub axle has flats for the bearings, so any change in hub design requires selecting bearing ID/OD dimensions to fit the Jowett part to a different hub.

Sorry for the confusion!

[Keith Andrews]

You may have to play with proporting valves front to rear also.

[David Morris]

Hi there,

The search continues! I assume that better brakes are the ultimate goal? Then, firstly, can I suggest that putting discs on the rear might probably be a waste of time, as the rears do very little in any system towards the overall braking effect ( contributing only 10 to 20% ) and it is always difficult to arrange a parking brake set-up. So, can I suggest we are just thinking about discs for the front axles? Assuming this to be the case, then I also assume that keeping the front stub axles would be preferable? Changing the front stub axles involves thinking about modifications to the steering geometry, Ackerman angles etc. etc., all of which sound a touch too difficult? The search then would be for discs that utilise the same internal diameter inner and outer bearings on our existing stub axles? Keeping ineer and outer ball races for the front axles was never a good idea, as ball races do not tolerate the side forces experienced here very easily. That's why we have taper roller bearings on the rear axle ( presumably inherited from Salisbury? ) and most other cars use tapers on the front axles. Jowett's started to play around with taper inner bearings on the front just before production ceased, so perhaps these would be a preferable match?

This is where I think the search gets a bit difficult? To keep the conversion down to the minimum without major machining, we need compatible inner bearing diameters and at least somewhere similar in the separation distance between the inner and outer bearings? Ideally, we need a donor vehicle that used to be drum brakes all round and was then converted by the manufacturer, in what was probably a long production life, to discs at the front? Without the parts in my hand for measurement, perhaps the Austin A35/MG Midget/ Sprite route might suit? It would be worth checking the diamensions, as the A35 drum braked originals led to the later Sprites/Midgets and there was a easy conversion route from drums to later discs. Another donor might be the 1950's Ford range, as the early Consul seems to share the existing front brake shoes with the later Javelins?

However, before we get worried about this, and bearing in mind the possible need for proportioning valves between front and rears when using discs, as has already been mentioned, it may be worth thinking about the relative advantages of either going for a full disc brake conversion for the front brakes or keeeping the existing drums all round and installing a servo on the existing system? I have no idea on the relative effectiveness between a drums/servo set-up and front discs/drums? I also suspect that adding a servo to a front disc set-up would result in a system that was severely over-braked? I am guessing here, but we might improve things by, say, a 30% improvement on a servo/drums set-up and compare this with, say, a 40% improvement using front discs, relative to the existing system.

Thinking about adding a servo to the existing system then looks to me to be a preferable choice, as this keeps so much the same but may well go a long way towards achieving the goal of better brakes? Might be worth considering and probably much cheaper than going for front discs, that might only give us a 10% relative improvement over the servo mix? You can purchase independant servos that sit in the existing hydraulic brake lines for around £120 and I would be anxious to hear from anyone who has done this conversion on a Javelin/Jupiter existing drum set-up?

I am very encouraged by the enthusiasium in this thread, and the earlier one about swapping engines, and it shows that we are not prepared to sit on our hands and keep things the same, just because that is what we have! Jowett's were at the forefront of development in the late 1940's and early 1950's and would have soon pushed ahead themselves with new ideas, had they still been in business! Disc brakes only arrived just as Jowett's production ceased and I am sure the factory would have been delighted to grab the chance to use them. ( Perhaps they did on the R1/2/x racing cars, and we never saw the results?? )

Please keep the ideas flowing, as we need to be a innovative club, adaptable to new ideas and responsive to fresh challenges. Indeed, it might be an idea to start a list of those more modern developments that help to keep our cars on the road. I can offer the use of polyurethane bushes in the later Javelin/Jupiter front suspension lower swivel pin bushes. The stock ones in rubber get soaked in grease and only seem to last a year before going 'squishy' and resulting in an MoT fail. Changing mine to poly ones from a MGB set is a direct replacement and they are still there in excellent condition five years later!

I hope these rambles help and best of luck in the search for continued development! Keep it coming!

David

[David Morris]

Hi there,

In the way of an update on my post above. my guess on the costs of a remote servo was too high! ( unusual these days! ) They seem plentyful on eBay and I have just seen a sample one going on a 'buy it now' basis for £82.50p, brand new, plus P&P! The eBay item number is 150470827318, if you are interested. Has anyone any experience of using such a system?

All the best,

David

[TedAllen]

Some interesting points there,David. Particularly in respect of front hubs and discs to fit our stub axles.
I would be interested to know where the calipers would bolt on.
I'm not for a change on my car now, I find the brakes very adequate for the motoring I do in it, but all power to anyone who works out and fits a different system.

Ted

[Jack]

Thanks all for your input.

Discussions while picking up a wheel and hub for the alloy wheel manufacturer lead down the route of servos for the brakes.

I think this is entirely feasible and a good idea, keeping the look of the car fairly original - and also cost effective - plus for lower powered engine conversions it seems to be adequate stopping power.

The project is likely to be approx 100bhp and 120 lb ft of torque, so not exactly earth shattering, more to modernise the car a little to help it keep up with modern traffic. On that basis, I am fairly confident that the servo will give us plenty enough stopping power, and should be an easy modification which can also be easily undone in future if required.

We will try and find some discs or a car which we can use brake parts from, however it may not be utilised for this project.

The other factor affecting my thinking is the need to then have hubs manufactured with the Jowett wheel spacing and setup, certainly seems to be different to almost every other car out there, so the chances of us finding brake discs on another car with a hub that will fit seem very limited - this would also add significantly to the cost, and also the time and effort involved in fitting such a thing.

Jack.

[Chris Spencer]

Jack - Please do not write off the front disc conversion just on hearsay - this is sortable and would be top of the list on any rodders list of improvements - it's pointless just doing a engine swop if you can not balance the braking system against the output of the engine - it just needs some research and a little thought.

[Moises Jr.]

I take a fotograph to the brakes of R1 in Cannon Hall, rear and front.

jowett 383.JPG

jowett 388.JPG

[Chris Spencer]

So the R1 ran with drum brakes all round but alloy drums with fins to help with the cooling.

[David Morris]

Hi everyone,

Yes, I expect Jowett's would have used disc brakes on the R1 had they been available? I have copied this from Wikipedia :-

'Reliable modern disc brakes were developed in the UK by Dunlop and first appeared in 1953 on the Jaguar C-Type racing car. The Citroën DS of 1955, with powered inboard front disc brakes, and the 1956 Triumph TR3 were the first European production cars to feature modern disc brakes.'

So, back in 1949/50, Jowett's had to use drums, although as you point out Chris, with alloy fins for cooling. I find my Javelin's drum brakes start to lose efficiency due to heat after going down a steep local hill that is about 3/4 mile long.

I am not suggesting that we should abandon the search for a suitable disc braked donor vehicle or even new fabrication, but we do, I believe, need to evaluate the relative improvement we might achieve with front discs over drums and then with drums with servo assistance. With an engine transplant, probably giving around 100% power enhancement, we would need to take brake improvements very seriously, as these would be essential.

Perhaps the single line hydraulic system we have at the moment should also be considered for a more modern split line master cylinder? The single line system is not really ideal if we use a replacement engine with around 100bhp on tap?

Hope this helps,

David

[Forumadmin]

Jenny' s Javelin has had servo brakes since the early 60s. Very good they are too, as Sir Stirling commented on last year. See picture http://jowett.org/jowettnet/dt/tech/mods/mods.htm

I do not think brakes are the problem on the Javelin; even when you fit sticky wider tyres. After all extra braking is not needed with a more powerful engine; it is only about weight and speed. You actually will not be going any faster with a more powerful engine; just getting there more quickly. After all, you will not be taking the car on the track. What is important is brake fade; and hence we fitted competition linings for competition. Thus the ducting through the back plate and fins on the drum in the pictures in this post.

Not to be forgotten is that fitting lighter 15" aly wheels will reduce the rolling inertia, and thus improve braking. Fitting lighter tyres also helps. Truck/taxi tyres are almost 50% heavier than the originals.

Also going on a diet would help Jack!

[Jack]

Jenny' s Javelin has had servo brakes since the early 60s. Very good they are too, as Sir Stirling commented on last year. See picture http://jowett.org/jowettnet/dt/tech/mods/mods.htm

I do not think brakes are the problem on the Javelin; even when you fit sticky wider tyres. After all extra braking is not needed with a more powerful engine; it is only about weight and speed. You actually will not be going any faster with a more powerful engine; just getting there more quickly. After all, you will not be taking the car on the track. What is important is brake fade; and hence we fitted competition linings for competition. Thus the ducting through the back plate and fins on the drum in the pictures in this post.

Not to be forgotten is that fitting lighter 15" aly wheels will reduce the rolling inertia, and thus improve braking. Fitting lighter tyres also helps. Truck/taxi tyres are almost 50% heavier than the originals.

Also going on a diet would help Jack!

I could alternatively refuse to take passengers The tyres will be modern 15" tyres that should be fairly light by comparison to the older style tyres, and the alloys are under investigation at Compomotive next week, looking very positive at the moment.

Having now bought what was going to be the donor car, frankly it is way too good to nick the engine and gearbox out of. That means that we can look to some alternative engine and gearbox setups, perhaps something a little more pedestrian, but still likely to be around 100bhp.

As Keith says, the aim is not to produce a car for race or rally, it is simply to have a car that can be driven every day (I know, you can drive a Javelin every day, but without significant time having to be spent on maintenance) and that will comfortably sit at 70mph on the motorway.

We should continue the search to see what we can find on the disc brake options, but it won't be necessary for this project if we use a servo instead. I doubt the car is going to be used in such a way that brake fade will be a major problem, as long as it can stop in an emergency I am happy, plus with a modern manual gearbox engine braking should be easily employed to avoid overheating the brakes.

Jack.

[Chris Spencer]

Jack - You are quickly becoming a lightweight - if you are going to do a engine swop at least make it worth the effort - whats the point of removing a 60 BHP orginal equipment engine which can be tuned to 90 BHP to replace it with something else of a 100 BHP - stick to your orginal plans - the donor vehicle has cost you peanuts. If you just want the Jav to be capable of overtaking the spoty kids Citroen Saxo on the A41 leave the original engine in and bolt a nitros kit to it.