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Help Needed
hicost - 19/12/10 at 02:12 PM

Hi all, merry xmas to you all.

I am playing with the front end of my car at the moment, in fact I have cut off all the suspension brackets and converted the last of the bushes on the lower wishbones to rose joints, so that means the complete car is now metal to metal. Anyway I have enclosed a small video of the help I require.

http://www.youtube.com/watch?v=Z6vN1cGR6I0

Please find a picture of turntables that look like if the wheel was on them then the distance could be say 30 to 40 mm on either toe in or out, its the distance when measuring it from nearly centre I am looking for as per the video.

http://www.langs.co.uk/images/SEAGA44.png

Looking forward to any answers.


James

interestedparty - 19/12/10 at 02:24 PM

If you tell me how far the rod is from the centre of rotation, I can do a quick CAD drawing and measure the distance at whatever degrees you want. (so can anyone else who has CAD, who needs trigonometry?)

hicost - 19/12/10 at 02:31 PM

quote:
Originally posted by interestedparty
If you tell me how far the rod is from the centre of rotation, I can do a quick CAD drawing and measure the distance at whatever degrees you want. (so can anyone else who has CAD, who needs trigonometry?)


Okay I have just measured it now from the centre of the shaft to the out edge of the disc, not quite as it appeared in the video, as I am going to have to move it in and out for the adjustment.

The answer is 145mm and I need to arrive at 20 degrees toe in and out so a sweep of 40 I guess.

Thanks for the help.

James

steve m - 19/12/10 at 02:35 PM

James

I cant help with the original question, but that shock looks a tad stiff for my likeing

Steve

robocog - 19/12/10 at 02:42 PM

http://www.ground-control-store.com/toe-out.htm

Regards
Rob

interestedparty - 19/12/10 at 02:43 PM

Well, the distance in a straight line from a point on the circumference of the circle (of 145mm radius) to a point on the same circumference after 20 degrees of rotation is 50.48mm (approximately)

And from that point to a point 20 degrees in from there is 99.42


You would be ok on the first measurement, because you only need to measure the gap between the witness point in the disc, and the end of the rod where it is now. Once you move the rod, it's all going to go wrong unless you move it in such a way the the end follows the circumference of the circle (as opposed to straight in, perpendicular to the chassis centre line.

interestedparty - 19/12/10 at 02:46 PM

What you really need is to cut a piece of curved material like a crescent that is just outside the path of the edge of the disc as it turns, fix it to the chassis, then we can easily plot the degree points on to it.

You say you've set the toe relative to the rear, but is the rear track the same as the front, or have you allowed for it if it isn't?

hicost - 19/12/10 at 03:12 PM

quote:
Originally posted by interestedparty
What you really need is to cut a piece of curved material like a crescent that is just outside the path of the edge of the disc as it turns, fix it to the chassis, then we can easily plot the degree points on to it.

You say you've set the toe relative to the rear, but is the rear track the same as the front, or have you allowed for it if it isn't?


As regards the track being the same or not, all I have done is used the centre of the tyre as it sits on the car at the back at this point in time. I am just using it as fixed point. I think I understand what you are thinking, but all I am trying to do at this stage is weld the brackets on and allow for the largest variable adjustment aroun 5 to 6 degrees of castor. I will get the car squared once complete again.

Thanks for the help so far, I did not think it was going to be that large an amout but hey hoe.

James

robocog - 19/12/10 at 03:14 PM

Not sure if it will work could someone please test and confirm :-)
clicky/

Regards
Rob

[Edited on 19/12/10 by robocog]

interestedparty - 19/12/10 at 03:21 PM

I can't open xls files, so can't say. I think Hicost's problem is that he can't put the wheel and tyre on, because of the caster gauge.

hicost - 19/12/10 at 03:24 PM

Hi Rob

Looks useful but I am working with one side of the car at a time at the moment.

I love these tricky ones, I bet the other side is quicker, its been like this for two weeks as I have not had much time to think or sort it out.

James

robocog - 19/12/10 at 03:25 PM

Doesn't matter about lack of tyre or wheel as it can be measured off the disk's diameter

Not sure if I can convert it to open office format...will give it a go

Regards
Rob

robocog - 19/12/10 at 03:29 PM

Ref only doing one side at a time...
Measure to the centerline of the car and double the distance results for the 2 yellow boxes

It shouldn't matter
the one side /should/ mirror the other if going in a straight line is intended once done :-p

Regards
Rob

[Edited on 19/12/10 by robocog]

[Edited on 19/12/10 by robocog]

robocog - 19/12/10 at 03:34 PM

And for completeness .... chose the version you want :-)
http://www.robocog.dyndns.org/locostbuilders/

Can anyone please confirm the maths is correct ?


Regards
Rob


[Edited on 19/12/10 by robocog]

[Edited on 19/12/10 by robocog]

hicost - 19/12/10 at 04:10 PM

Well using the measurements provided I bent a bit of rod in a rough radios around the total 40 degree swoop of the disc, and the suspension brackets are spaced apart from the bottom ones via a fixed gap spacer and it all seems to look okay and the reading is within the tolerance I had mentally set to 5 /6 degrees castor. I knew I needed more castor and could not achieve it with the brackets where they were so cutting it all off has proved correct. If allot of work.

I recommend one of those Sealey gauges, works it all out great.

Thanks all for your help.

hicost - 19/12/10 at 04:14 PM

quote:
Originally posted by steve m
James

I cant help with the original question, but that shock looks a tad stiff for my likeing

Steve


Sure does Steve, hey reading your post about computers, I can sort you out another base unit with good size hd and windows XP in exchange to a liitle modifications to my nose cone. I have quite a few systems in at the moment some less than 24 months old.

James

bob - 17/1/11 at 08:35 PM

Have you sorted this yet James