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Smokey's JW4 Formula Four Rebuild Thread


Mark (smokey mow)

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XTR2Turbo

Top work.  You remind me I need to get my powder coat kit out of deep storage ..

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Final picture for the day before I zipped the car back in its Carcoon .  

Or is it… About a year ago I posted on this thread that I was hoping to have my car completed and running in time for the 50th Anniversary of that first race, and I’m sure many of you may now be wond

Only a small update as I've been back on the DIY for the last couple of weeks.   There's not much left to do now but one of the jobs was to fit the chain.  This was on the list to do a few w

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looking good Mark - how long until the "casting stage"? looking forward to seeing the results of that :d

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Mark (smokey mow)

looking good Mark - how long until the "casting stage"? looking forward to seeing the results of that :d

Just for you Dave i shall skip ahead for a moment.

As i mentioned earlier on the rear axle from the car had been stolen, and as my quest to find past owners has been less than easy, the search for spare parts languishing in garages has been equally difficult so the axle is one area where I'm going to be forced to break slightly from originality.

One choice i made early on in the restoration is that I would only use parts and upgrades that may have been used or carried out "in period", In the case of the rear axle this means I've chosen to use a Mk1 mini differential which will be converted to chain drive and with shortened shafts.

Reconstructing the rear uprights is going to be one of the most costly a difficult parts of the build as originally they were cast magnesium and the long term plan is to sand cast a pair of replacements. Before I could even think about the uprights the first hurdle to overcome was establishing the original geometry for the rear suspension and the wishbone lengths. This took a bit longer than planned as it's needed quite a bit of drawing work doing, but ultimately from the known data of ride-height, rear track width, shock length and a few photos it's been possible to establish the original wishbone lengths.

No pictures yet I'm afraid but first off I needed to purchase all the components needed (axles, diff, hubs, bearings etc) so i could take the necessary measurements needed to draw them.

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Expect to see some 3D models soon :d The provisional sketches i've made so far for the uprights suggest it's not going to be possible to cast them in a 2 piece mould, and more likely I'll either need a 3-piece mould or 2 wax pattens, both of which will push up the tooling and casting costs.

With so much money involved, the current plan is to mock up the rear suspension using the mini front uprights i have but with some appropriate bracketry made to lock them in the straight ahead position and also recreate the JW4 geometry. Here's a teaser for now.

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Using the mini uprights I can tweak and prove the design at a cost of only a few hundred pounds before committing several thousand for the new cast uprights.

For this Allan Stainforth's book "High Speed Low Cost" has been very helpful as has Rob Macknay who collaborated with Allan on the republishing of the book. Rob has kindly sent various photographs and technical information on the rear suspension of the Terrapin which uses a very similar suspension design to what i propose to uses for my initial build. A similar system was also adopted on the Mini Twini (a twin engined prototype car with one in the rear and the other at the front) this one conveniently just up the road from me at JD classics.

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This is pretty much the stage I'm at right now, and once I'm happy with the rear uprights I can then finish the manufacturing drawings for the rear wishbones so i can get them made. The plan at the moment is to have the car rolling on it's own wheels by spring, but I'll see how that goes :)

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  • 2 weeks later...
Mark (smokey mow)

So to bring this thread right up to date this is the progress as of today.

In a effort to try and get the car rolling I've been busily working on drawings for the rear wishbones and axle. The rear dampers and the lower wishbone share a common mounting point on the upright so it's been easy for me to work out the length of the lower wishbone based on that.

I was fairly confident in my measuring and drawing but as a double check, i fully assembled the front of the car to confirm the width and ride heights were correct in my drawings. Which they were :d

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At he same time also needed to confirm the position of the diff as it will need to be offset in the chassis to align with the engines drive sprocket, so I loosely fitted the engine into the chassis. As it turns out there's plenty of room in the engine bay for the little 500 twin. Once I've finished the drawings for the bearing carriers I'll then be able to order all the parts for the chain drive diff conversion

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Aside from the axle the only other area of the car where I shall be breaking from period is the location of the fuel tank. The tank would have originally been located in the nose of car ahead of the steering rack. As if it's not enough to already have my feet hung way out the front and my toes as the only crumple zone, the thought of 2-1/2 gallons of fuel above my ankles frightens me a bit. Assuming they'll be enough room, the plan is instead to put the new fuel tank in a much safer place in the centre of the car behind the seat ahead of the engine.

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Mark (smokey mow)

Apologies that some of the pictures may have gone missing :oops: I appear to have maxed out my Photobucket account and need to upgrade :down:

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Hey Mark, that's quite a teaser without the pics  ;)

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alexander72

I cant see the pics eaither - says I have to upgrade for extra bandwidth

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Norman Verona

James, it's not you that needs to upgrade - It's Mark. But you know that, don't you :)

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Tom (T3OMF) - Cotswolds AO

Apologies that some of the pictures may have gone missing :oops: I appear to have maxed out my Photobucket account and need to upgrade :down:

 

Mark, just open another account with a different email address

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Mark (smokey mow)

Mark, just open another account with a different email address

that wont work :down: the issue is not the quantity of photos but rather the amount of people that are viewing my images :oops: don't worry folks I'm on the case and normal service shall be resumed shortly.
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alexander72

I didnt know that Norm - i cliked on the picture and it ssid upgrade - computers are not my strong point mate - great thread Smokey - well done mate 

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