Isetta steering worms.

[AndyL]

Happened to see these two steering worms on ebay. What I found interesting is that the thread style is different, with one having a v-style thread and the other a square thread profile. I am guessing the square thread was the later profile which would lower friction a bit

[Bob Purton]

Hi Andy. MIne is a 1959 car and has the V profile steering worm but I was told the square cut thread is better so I managed to get hold of one along with its matching nut last year. I still havnt got around to fitting it. I don't know if the square cut ones are latter but it will be interesting to see if it makes any difference in the feel of the steering.

[AndyL]

In theory a square thread for the same lead angle should give about 15-20% less friction than a V-thread.

I'm pretty sure replacing the silentbloc bushes in the steering linkages with plastic polyurethane items would help a lot too. Greg Hahs does a kit, but it's far from cheap.

I remember years ago foolishly agreeing to change the silent blocks on the lower front suspension arms of a members car. Club had got a bad batch and lots of them were failing. I got a phone call from someone local after the IOC published members details. He asked if I could help, although I soon found out that it really meant fix my car because I don't have a clue!

The chaps entire tool kit seemed to consist of a Black and Decker electric screwdriver. I did fix his car, which was far from an easy task as it involved stripping the car suspension apart in a unelectrified lock-up in the wintertime, plus the club were out of stock on the silentblocks.

The chap was supposed to be there to assist, but always seemed to be called away to an urgent meeting whenever I went around. 

I'm older and wiser now.

[Bob Purton]

Yes, I changed all my silentblocks for new when I got the car but next time around I think I will use rod ends on the link/track rod and polyurethane bushes everywhere else.

I do wonder why BMW use an acme thread on the steering worm in the first place. I guess a square worm may be harder or more expensive to produce.

[AndyL]

The V-thread may have been an attempt to cut down or remove shimmying caused by the single rod actuation of the steering mechanism. That's eliminated with the fitting of a steering damper, but not all cars had one fitted, mine include, although the bracket on the chassis is there for one to be added later. Was probably an optional extra, and shouldn't really be needed until the steering developed some wear and tear

[Bob Purton]

Mine has never suffered with the shakes and I dont have a steering damper. I wonder if my radial tyres help in that area? Although I replaced all the silent blocks and the front shaft bronze bushes I think I need to do the outer bush again. I think I reamed a little too much material out and there is some play there now. I pump it full of grease and it firms up but only for a few hundred miles.  What tyres are you running on?

[AndyL]

My car isn't roadworthy yet, still being rebuilt.

The car still has its original Dunlop goldseal tyres, although they're knackered.

I will probably go for Falken radials when I get to that stage, Terry Parkin runs those and says they fit well on the rims and don't require spacers to clear the shock/spring towers.

[Bob Purton]

Terry is correct, that's what I'm running on, excellent tyres and not too dear either.

[AndyL]

I think the original crossplies look more appropriate as they sit on the rim better, however if you intend to really use the car I think radials are a much better option.

[AndyL]

Got my steering box top off today, I have the square style thread on my car. So interesting, I think they fitted whatever they had available.

[AndyL]

Next job is to pop the steering wheel of the shaft. Going to make a puller, and  think a bit of heat may help. Anyone got any good tips to pass on?

[Big Al]

Only that tension, plus shock from a mallet, is more efficient than whanging on mega pressure to break the taper. But you know that. The tool made will fit a number of other vehicles, so its handy. I have an original Goggo one, made out of parts of the rear shaft puller set as intended, very neat. So far it only did not fit the Schmitt, which has an awkward and offset angle. Really you need both a nut and handlebar puller to make a neat job of that installation. I have the puller available, now I have Russell's stock, but its a bit of a sledge hammer to crack a nut on anything else, £30.

[Jim Janecek]

Next job is to pop the steering wheel of the shaft. Going to make a puller, and  think a bit of heat may help. Anyone got any good tips to pass on?

I gave up on pullers and whacking it with a mallet after I discovered that a small 12-ton press works great.
The wheel and shaft fit nicely into the confines of the press, then it is a simple matter of pressing the shaft out, rather than pulling the wheel off.
The most stubborn wheels just pop off with very little effort, no heat needed, and certainly no damage.  (unless you screw it up somehow...)
I bought a very small 12 ton press 10 years ago for around $100USD. It takes up very little room and I have used it for all sorts of things over the years.

If you don't have a press, find a friend that does.  That's what friends are for.   

[AndyL]

I know exactly what you're talking about, but I don't really have the space for a tool like that- I've seen the size of the garages you folks have in the US.

I do have a couple of small bottle jacks, not 12 ton, but probably good for a ton at least, I would think that would suffice to pull the wheel off, so I could put something together that will get the job done.

There is also a hydraulic press I can access at work, so I might give that a go. I take it you pressed against the bottom of the aluminium hub?

[Big Al]

Tight on the hub and protect the threads on the column. If pressure is not square and controlled it can either turn or bell the end of the shaft. Most shafts are made of surprisingly soft metal. If anything touches the plasticised and caste in parts the damage is done before you notice. So be certain the area is clear. With a correct puller I have never had a failure other than when Mr Botch has stepped forward. Like welding the wheel on etc.
Hydraulic press is really useful but its the box of handy scrap used as dollies that gets in the way! I have about 3 bakers trays of them, now I have manufacturing tooling. Comes with the territory.