Adjustable A frames

[alexblack13]

Hello Guys..

I see...Said the blind man. I understand now. Internal diameters of the 'A'frame bush mountings. Big ones and small ones.

Got it now... Hic'... Sorry Brian...Your question now appears answered though.

I broke a flamming big Vice trying to push out one of the larger inner bushes. Bugger! Had to go and retrieve my spare which is now sat on my bench. Set up my hydraulic press this morning and pressed out all the bushes on 4 frames in jig time. Now why did I not do that to start with.... Doh!! Dingbat!

Cheers guys.

[bcmc33]

Paddy,

John knew exactly what I was asking for - it was just his usual stiring engineering humour getting the better of him.

[alexblack13]

Yep!! Guilty as charged !!

I was just plain dopey! Didnt think the thing thro' Sorry...

John had it answered anyway.... I'm just going back to sleep!

Alex...

[alexblack13]

Hi Guys,
Finished the 'project'. Not too expensive or time consuming really. Pic's below will let you see how I ended up doing it. Following on from the previous set. The only thing I could not live with was just plain butt welds via the mig. I ended up with a re-enforcing 'tube' (I split it to allow a weld along the length attaching it to the tube below) I also ended up with a 'plug weld' on the end of each piece down into the tube below. I think they are well strong enough now.

See what you think. I will be keeping a close eye on them for a while never the less & I will advise of any issues found.

For a starting position I 'centered' the adjusters.Turning them 'till there was freeplay. IE the tube was neither in tension or compression, then I wound on (extending the length) 1 turn on the turnbuckle. This, I estimated would push past the original setting and also provide a small amount of toe in more than original. Gotta start somewhere. I will line up with more care when I have the car re assembled. I'm then taking it for full setup / alignment check.

Here are the final pic's. These A frames going back down to Geoff (thecyclist!) who kindly sent me 4 off for trial purposed. 2 off which were usable. You will have these back soon Geoff.. Thanks for your help..

[Jas]

Hi All

Now I have done my A-frames too.
Thanks for the turnbuckles Alex.

I made an smaller diameter tube to go into the A-frames where I welded it back together to reinforce the joint. Also the threaded bushing was TIG welded around the edge to stop water from getting in that way.
It took some double checking before cutting the A-frames and also a lot of additional measurements under ways, but I pleased with the end result and they adjust nice and easy.

Using the M12 thread it should adjust the toe about 2? for one full turn of the turnbuckle.

So now it out with the old bushes and of to the sandblaster before painting.

Thanks to everybody for the help on the way.

[alexblack13]

Lookin good Jas! Just need to set it up now. Easy!

Alex B

[spanner]

Nice work gentlemen.

This information (AC 43-13) on welding, splicing, rosette spacing, etc. of aircraft tubing might be of interest. Scroll down to around page 4-68.

http://rgl.faa.gov/REGULATORY_AND_GUIDA ... r%2004.pdf

Spanner

[alexblack13]

Great bit of info' that. Thanks.... I hesitate to call you spanner but I have no choice, sorry.

Very useful in many respects and will help anyone else doing a similar job. (Pay attention you lot!)

Thanks from us all...

Alex B...

[elansprint71]

Coming to this a bit late but might be of use to others in the future. Did you try heating the "stuck area" with a torch and then trying to move the turnbuckle? Usually works wonders.

I am a Mech Eng and have always believed that if you don't have a big enough hammer, it's time to get the torch out.

[alexblack13]

I didn't Pete. But boy was it stuck. When I cut it out I cut thru the joint and freed the turnbuckle off just to have a look-see. It would not have freed off I don't think. (I too am a mech eng)

The Mk 2 method is still the way to go as described above. You really need to remove some pipe and replace with the modified parts.

Anyone need some turnbuckles to do this job? I still have a few pairs left with the lock nuts. Just a small cost + postage to you guys.

Alex B....

[billwill]

I'm not really inclined to do this to mine. Wheels seem to be lined up OK for road use (If I ever get a new head ) but looking at your work it looks as if it is a brass turnbuckle in steel bushes is that right?

If I were designing it I would be more inclined to using a steel turnbuckle with brass bushes. Two alternative fixings come to mind.

(a) Is the tubing thick enough to tap a fine-ish thread on the inside then screw the brass bushes in and prevent from unscrewing with grubscrews? But maybe the gap would have to be too big to enable the turnbuckle to be fitted in, I suspect you would have to turn the turnbuckle while screwing in the bushes so that it ends up central. H.. using the same thread pitch for bush-to-tube as turnbuckle-to-bush would help there..

(b) using a high temperature brass for the bushes, they could be brazed or silver-soldered in, using through-tube- holes like you have done.

(c) even maybe soft soldered in with lead solder, but I'm not sure if that would be strong enough. or corrosion proof.

[gerrym]

Bill, tubing is too thin and probably not perfectly round - don't think tapping would work at all. It would also be tricky to align the tap with tube.

Regards

[alexblack13]

No Bill. They are not Brass Turnbuckles! They are plated steel. The adjustable A frames are more or less a direct copy of the commercially available items from a couple of well respected sources. Only one uses ones own original A frame parts.

Answers to your questions..


A) = No..

B) = Use steel. NOT brass and WELD OR Braze the components into place.

C) = I personally would not drive my car with soldered suspension parts. Are you serious or leg pulling here?

Lotus rear suspension alignment IS an issue. Hence Spyder / Kelvdon and others designing this adjustable component. We have only copied it & they cost peanuts to modify your existing A frames. I thought much better than forking out over ?200 a pair from Spyder for E.G. The Spyder and others products are superb by the way and worth the money in my humble. I just chose the diy route me being me and having the kit to make them.


Alex B....

[billwill]

>C) = I personally would not drive my car with soldered suspension parts. Are you serious or leg pulling here?

Leg pulling to see if everyone is awake, though if a brass insert was about 4 to 6 inches long and soldered on all the interfacing surfaces it might be OK. but harder to do than the other methoids anyway.

I suggested brass (or bronze) for the bushes as they would be unlikely to seize together as your first try did. Same reason we have brass nuts on the exhaust studs and bronze as the trunnions.

[Elanintheforest]

Ken Myres was showing folks at the Malvern show an adjustable offset pin that he'd had developed for adjusting the rear toe-in. Looked like a very simple solution to me and just replaces the outer A Frame bolts.

But I am confused with all these fabulous engineering solutions. Surely the cars were set up correctly when new, and now if they are not right, wouldn't it be better to address the source of the problem rather than mask it with a workaround? Or am I missing something really basic here! I can understand the need for adjustment on racing suspension for the track...but for a road car??

Mark