Hi,

I am nearly at the point of finishing my subframe and sending it for welding. The one are that needs resolving it the lower control arm mount to allow adjustment.

I have been looking at this for ages and the best way to acheive what I want looks like making new lower control arms for my car and leaving the frame as is.

Welding them up could be done but they would need x-raying to pass engineering.
Expensive, but maybe not as expensive as what I'd rather do which is have them machined up. These would pass cause they aren't welded.

I've very roughly drawn them up in sketchup in a bid to see if any more knowledgeable engineering types may be able to offer advice. The adjustable bit in the first photo is an off-the-shelf item. $36 with both nuts. It's 3/4 inch, not sure of the thread.

Alternatively does anyone know where I can do a machining course and make them up myself? In Melbourne?

What faults are there with my basic design? (bear in mind it is very rough and not to proper dimensions)
Are we talking ridiculous money to get them made?
Would they be strong enough?
Would mild steel be best?
Would there be advantages to doing a run of them if anyone else want adjustable arms for there Morris 1100??









Thanks
Madmorrie[/img]

A 3/4" thread made from mild steel will not be strong enough for that application.
I know that the after market adjustable arms for minis are constructed similar or a thread thru a sleve , BUT has any-one actually thought about the forces applied to a L/H - R/H threaded rod in that application. Consider the turning force from the radius arm as the bottom control arm moves up and down.
Time to think out side the square and look at other cars and see how they are set-up for adjustment for a SINGLE control arm.
The first thing is to calculate what the total increase of length is required to get the required camber. Then look at alternatives, like cam adjusters either top or bottom arms etc.etc. I am sure you will figure something out.

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David, thanks for your input.



Obviously I was thinking of basing the design on this type of thing? Has anyone had these fail in service? Going to a spherical rod end in the inner end may simplify it a bit but I was hoping to avoid that.

Was planning on sourcing the adjustable bits from here.
http://www.mcdonaldbrosracing.com.au/tubeadaptors.html
They make them for drag car suspension so I figured the bits would be strong enough. However I am not an engineer.

I worked out I only need to move the pivot by 3.2mm per degree, so an eccentric should be able to achieve this. My difficulty lies in incorporating the slotted holes accurately into my frame to allow an eccentic bolt to work, and reliably hold its setting, and be strong enough. (Note that I plan to box the lower mount in once I sort it out)


Cant see it in this pic but it shows the mounts. The rear hole is 3/4 and the pivot bolt is to be 1/2 inch. I did think I could drill out the front one to 3/4 as well and run an eccentric stepped washer in each hole, then mig them in place once adjusted, however this means the bush inside does not run on a flat, or even concentric surface, which would probably not help their service lives.

I still need to do another run around the wreckers but most I've looked at seem to have the same system with bolts like this.


Please note I am not trying to dismiss your suggestion, I certainly value the views of someone like yourself on this. I keep swaying between the two options and would really like to find a solution so I can get on with the bloody thing...

Madmorrie

By the looks of things the drag racing threaded inserts don't look all that great. Have to ask them what they were designed for, ie hard cornering forces and a drive force from a fwd car.

Good luck with the problem, its definitely a tricky one.

_________________
Simplify and add lightness

Transport will NOT allow spherico rod ends. The std ones the plain sperical brg is only pressed into the outer housing and can come out very easily.
The type used on race cars have the brg pressed in and held in position by a shoulder on one side and a circlip on the other.
The problem with a L/H, R/H thread is that as the radius arm tries to twist the control arm either one of the threads is trying to un-screw.
I have come across a couple of minis that this has happened to. The nuts may not have been tightened up corectly, but??????? they were loose.
As for a cam type arangement have you thought about setting it up on the top arm instead.
On minis there is one large hole in the subframe for the pin/washer, and a 1/2" hole at the back. If the rearhole was opened up to the same diameter as the front then you could use a stepped washer with a off set 1/2" hole drilled in it.The other washer needs a 1/2"unf thread so it can screw onto the pin and tighten up. This will allow the pin/washer to be rotated and then this will create a cam effect. The whole lot can then be tighted up as per original set-up. The top arm has needle brgs and the arm will rotate around the shaft with less turning force that the bottom pin/ rubber bush

Just an idea,but!!!!!!

_________________
Research is the difference between speculation and investment. Anyone who copys some one else will always be second
www.minisprintgt.com

Hello
Do you actually need it to be adjustable? If you make it the right length, would you need to ever adjust it again? I ask because a way of doing it might be to weld up the balljoint hole and have it redrilled and reamed further out on the arm. I know officially its not allowed but it still has all the original surronding material and it not visible if done properly. It was an old trick for group N racers who were not allowed adjustable arms. Its only a matter of a few millimetres that the hole needs to be moved. You could make up some basic adjustable ones to put on wheel alignment machine and then copy the length over to the fixed ones.
Corey

Hi,

Yeah, I don't actually NEED it to be adjustable. But my engineer agreed that it would be a good idea, especially given the mods to the frame, to allow some adjustability to get it handling well. While nothing should have moved far, and in some cases may not have been that accurate from the factory, I'd like the chance to set it up right.

David, I like your thinking about moving the top arm. Much easier to implement on the frame due to better access, however the on car adjustment may prove trickier. Still, you only need to adjust it once. Also I wonder if a misalignment with the suspension unit of a few mm would cause problems. I spose it already has to allow for movement so may not be an issue. I'll look into it.

Thanks all
Madmorrie