Okrasa Special

[johnM]

Wow even that piece of scrap really gives you a great hint at what the special will look like, really cool.
Great thread keep the up dates coming.

Kind regards

[911hillclimber]

Ha!
So good to see the action starting!
I had thought yopu had both started ages ago and were hiding the first bits from us...

Steep learning did nobody too much damage. I would keep that first roll pinned on the wall for posterity.

how often do you need to anneal the alloy to get those depths of bowl?

Keep going!

Graham.

[steve wright]

Graham, that's a great idea, although I think Barry has already put his knee through it!

[hot66]

fantastic work Barry

Steve, bet your really chuffed now you can see the special coming together ?

[steve wright]

very chuffed although I'm not sure on how aerodynamic the wooden bits will be on the back straight!

[Barry]

Ha!
So good to see the action starting!
I had thought yopu had both started ages ago and were hiding the first bits from us...

Steep learning did nobody too much damage. I would keep that first roll pinned on the wall for posterity.

how often do you need to anneal the alloy to get those depths of bowl?

Keep going!

Graham.

Graham, no annealing at all, believe it or not. In fact you can go quite a bit further using just the wheel.

This does give the advantage of ending up with a fairly hard panel, which is no bad thing given how easy denting full-soft aluminium is. Where it gets welded will be pretty soft though, although the planishing afterwards would part-harden it again I guess.

Had a conversation with Rod (my metalwork mentor), and it seems that my .002" might at well be 1/2", so back to the drawing board.

When I finished on John's car for the day, I returned to Steve's workshop for another look. Turns out that the runout is actually down to the shaft rather than the wheel. As the wheel isn't super-tight on the shaft, I did try the trick of centre popping the appropriate side of the shaft, and mounting the wheel in the best position relative to the pops. That lost another .0005 of so.

So, new plan. I'm going to machine up a holder for the diamond lap that will mount where the bottom wheels go. I'll also make up some sort of socket to go between a low-geared drill and the shaft. With the addition of a moat of some sort around the lap to hold some cutting fluid, this method should deal with any shaft and wheel run-out for good. We'll see: at least it's a plan.

There is an alternative, and that's to machine a new radius onto the shaft, and then convert the top wheel to ball races. It's a common mod, as the main shaft now becomes dead, and the rotation is dealt with the top wheel's new bearings.

The reason it's sometimes done is less about accuracy, and more about inertia: the combination of the top wheel and the shaft tots up to quite a mass. Obviously each wheeling of a panel requires 100's of forward and reverse strokes, all at a less than ideal height from a shoulder's perspective. Therefore some people favour a lighter stroke.

Personally, I rather like the weight of the top wheel and shaft, and that's how I'd prefer to keep it .

An update (warts and all if appropriate) to follow soon ....

P.S. I've mailed Hoosier's in the States (suppliers of very good top and bottom wheels) to see at what point run-out becomes a problem.

[Macaulay]

Wow, that piece of "scrap" realy got me excited!
This car is going to be great, I can feel it!
Great work Barry.

[Barry]

Thank you: Steve and I have go to be very good and concentrate on making the buck as good as possible, which will be another month at least I would think.

Mind you, it might be hard to resist having a little go at a few bits, purely for scientific purposes of course ....

Might have come up with a better way of driving the E/W for it's top wheel re-shaping. Update after the weekend.

[steve wright]

Cor, after this weekend I have to say I've never seen a man so in love with a bit of machinery. In fact my wife commented after we left that if ever a man represented the image of a pig in muck Barry was it! I'm sure Barry will post photos and details, but it's hard to convey the amount of enthusiasm he has in words and pictures. I don't often stop to think about what an extraordinary bit of fortune it was to persuade Barry to do the Special bodywork, but I'm damn lucky he said yes. GO BARRY!

[Mike Smith]

Steve,

Don't forget to change that VW Steering box for a ZF Unit

Mike

[steve wright]

hmmm, go to a Porsche unit you think? how much better will steering be improved do you think Mike?

[Mike Smith]

Yes without question - a much nicer box although a RHD Version is not a cheap option

The drop arms are different to LHD and more difficult to find

[Barry]

I seem to be getting un-healthily obsessed with this wheel .

Lets say you had .002" run-out in the top wheel, and the same in the bottom. As you wheel a piece of sheet back and forth, the top and bottom wheels are behaving like very slight eccentrics (not unlike me then).

So, as the metal goes through, at some points it may be that the two tolerances complement each other, giving no effective run-out. At other points R/O might not be too bad, and at the worst point, you'd have an extra 'squeeze' of 004". This doesn't sound too bad, but thats a big percentage of, say, 24 gauge sheet (which is only .022" itself).

The other issue is that once introduced to the wheels, the panel doesn't slip. Therefore if you have a loose part of the rotation in one place, and a tight part in another, you'll repeat that all the way along the panel. This starts to produce a bulge in the panel. The bigger the panel, the more apparent the distortion.

This is one of those rare cases where there is no minimum tolerance really: one thou seems to be the point where even on a stiff wheel, problems are unlikely. Trouble is, wheeling is not overly scientific, i.e. a lot comes down to feel. If you know you have run-out, it's going to be there at the back of your mind ready to pounce as soon as you get a problem panel. Is it me? Is it the metal? Of course, there's always that run-out I could never get rid of ....

You get the jist.

Anyway, with the above in mind, and as hinted at earlier, I decided the best way of getting round this was to turn the whole English Wheel into it's own lathe. Rather than using a cutting tool as such, I'd re-use the diamond lap from before, but in a machined holder that would fit where the bottom wheel lives.

I routered out a big MDF pulley (which was a real success, very useful to know if you ever need to quickly gear a motor right down for a one-off job), and set up as shown below. My little lap holder had a small reservior built in for the suds (Fairly Liquid and water), and has a jack at the rear for holding the lap steay on the wheel.

The motor and gearing gave around 120 rpm, which was perfect: fast enough to do the job, but not so fast to produce a rooster-tail of grubby lube over Steve's 911.

Anyway, to a point, the setup worked very well indeed. Straight away, and with the motor in action, it became apparent that the main shaft was badly bent, hence the problem at the 'nose' of the shaft where the wheel mounts. With this in mind, it's just as well I didn't go for a new (hardened) wheel, as there's no way I'd have been able to lap that out. With my setup though, the bent shaft becomes irrelevant as the whole assembly is being turned as one (which was the whole point of course).

Quite quickly I halved the problem down to one thou, so technically within acceptable limits. I wanted more though (don't we all). Bottom line was that the wheel didn't want to give any more. I reckon I ran the rig for twelve hours in total (I said I was obsessed), moving the lap position a tiny bit left to right every few seconds (otherwise it just started rubbing: you could hear the difference quite easily).

In the end, it just wouldn't go down past the 001" whatever I did. I concluded that the new problem was that the ball bearing race in the front of the frame probably had a little corrosion / wear / chatter in the races and balls. I'm guessing that this could easily jiggle the top wheel by plenty enough to give this error.

New bearing now on way (new old stock), the orginal BTW was dated by the bearing supplier as being 'probably pre-second world war' because if the maker's name, which changed just after the war . As I said to Steve, I think that being the case, I can forgive it a slight error. If the new one lasts another 65-70 years, it'll be good value.





All of this messing about did, I'm afraid, mean no progress on the Special itself this week I'm afraid, but hopefully will catch up this coming weekend.

BTW, New ball race due in a day or so, and I'm hoping to pop up one evening to try it out .

[Barry]

Cor, after this weekend I have to say I've never seen a man so in love with a bit of machinery. In fact my wife commented after we left that if ever a man represented the image of a pig in muck Barry was it! I'm sure Barry will post photos and details, but it's hard to convey the amount of enthusiasm he has in words and pictures. I don't often stop to think about what an extraordinary bit of fortune it was to persuade Barry to do the Special bodywork, but I'm damn lucky he said yes. GO BARRY!

Sorry, just seen this: thanks Steve, I think that's the nicest way I've ever been called a sad git .

Seriously, I'm really enjoying the whole excercise, from the first piece of wire, and gradually seeing a 'car' albeit a mock-up coming out of the wire-n-paper. Now with a bit of woodworking (which is always nice anyway) we're getting closer to the moment when Phase I will be officially complete, and the sheet-metalwork (dare I say, panelbeating) can begin.

If the wheel is also as close to possible to being perfect by then as well, I can at least be happy in the knowledge that any problems that arise thereafter are going to be of my own making, and hopefully therefore be resolvable given time and patience.

Good times .

[Gary71]

Where is that round of applause smiley when you need it!!

Obsessive? Not our Barry

Love the motor set up, you should have popped some metal through whilst it was running and checked how far across the workshop it went!