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PostPosted: June 19, 2015, 12:27 pm 
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I don't want to muddle the conversation but I'd like to include what I have done for Car9. Hopefully we can discuss this too. Ideally I'd like these tabs to be totally robust and yet tear away at the right amount of stress just before the vertical frame tubes are ripped out instead. Also they are intended to allow the suspension to be adjusted until I/we understand wants wanted for a persons car.

In this picture the bolt should be closer to the centerline of the tube a bit, the drawing needs to be adjusted. The bolts go thru sleeves welded into the vertical tube. I'm intending to use a 1/8" wall tube for the sleeve, weld around it and have the sleeve about 1/8" proud of the vertical tube. Some people might prefer to grind the sleeve flush...

Material and thickness of the tabs is an open question, but the nice thing about bolt on stuff is you can change your mind. The picture shows washers welded or brazed where the bolt holes are and I'm not sure that would happen in real life, sometimes I just get carried away with drawing...


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PostPosted: June 19, 2015, 12:53 pm 
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horizenjob wrote:
I've taken a few wheels off my formula car rapidly. I've even managed four at once :rofl:. I could go looking but I remember rod ends bent 90 degrees in the threaded region but don't recollect any that broke apart in the threads. I guess it would depend on high a grade steel you use in the shank. For wear reasons you want rod ends or sphehrical bearings with large balls ( I guess it's the opposite with drivers... ). So I think good rod ends made of more normal steel make sense, then they won't break?


like this??

Attachment:
BIT-XIsCQAA22Ib.jpg


Attachment:
RTEmagicC_image3_01.jpg.jpg


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PostPosted: June 19, 2015, 1:09 pm 
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horizenjob wrote:
I don't want to muddle the conversation but I'd like to include what I have done for Car9. Hopefully we can discuss this too. Ideally I'd like these tabs to be totally robust and yet tear away at the right amount of stress just before the vertical frame tubes are ripped out instead. Also they are intended to allow the suspension to be adjusted until I/we understand wants wanted for a persons car.


Marcus, i don't see how these tabs are adjustable. Wouldn't you also prefer the arms to bend rather than the tabs breaking? I would think you would want this method of failure, Arms, tabs, chassis... no? Maybe you already looked at this...

why add a boss instead of using just a regular washer or a thicker tab?

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PostPosted: June 19, 2015, 1:44 pm 
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The tabs themselves aren't adjustable but you can easily change then out for a pair with a different hole location. The bosses increase the bearing area and the resistance to tear out. Washers wouldn't do that but a thicker tab would. The only advantage of bosses would be less weight.

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PostPosted: June 22, 2015, 5:28 pm 
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mjalaly wrote:

like this??

Attachment:
BIT-XIsCQAA22Ib.jpg


Attachment:
RTEmagicC_image3_01.jpg.jpg


If the design is good and the rod-ends are set up correctly, there is not enough bending load to be concern with. You want the axis of the threads to be in line with the tube and you want the tube to point as close to the center of the ball joint as possible. This will result in all loads being reacted as tension and compression instead of bending. The only load you can't really control is the shock attachment but as long as it is close to the ball joint, the resulting bending is very minimal.

I'm guessing the broken rod-end on the push rod resulted from a bearing that didn't have sufficient travel and the broken rod-end in the second picture is because the threads are not in line with the arm. If you're going to use this design to adjust camber, you're safer doing it on the uppers since they see much less load.

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PostPosted: June 23, 2015, 8:59 pm 
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@mjalaly do you have any way of adjusting your camber or did you just go for set it and forget it?

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PostPosted: June 24, 2015, 11:59 am 
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Caster I did set and forget @ 5° but camber is adjustable. I have designed in 2° in the front and 3° in the rear. From there i can add shims to adjust to exact specifications.


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PostPosted: June 24, 2015, 6:41 pm 
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Very nice, that is a really cool design..
3° seems a lot in the rear but if it works it works. I have about 1.75° in the front and about 1.25° in the rear. If I go higher in the rear it increases wheelspin dramatically. I would like to dial in more dynamic camber though as it could use more in the turns.

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PostPosted: June 24, 2015, 8:13 pm 
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I would like to dial in more dynamic camber though as it could use more in the turns.


In the endless circle of compromises - then you land up with wheelspin again when the car squats under acceleration. High power cars ( lots of cars compared to the 50-60 HP in the old days ) have more trouble with their compromises or maybe more accurately give up more just to put the power down...

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PostPosted: June 24, 2015, 8:16 pm 
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It looks in the picture above with the broken rod ends that they are just too small. I understand something has to break, but one does worry a bit about stress in the threads - so a step up in size there seems a good idea. The strength goes up rapidly and I don't see why someone would save an ounce or two there when they are also landing up with smaller bearings that could wear out quicker.

I did pull out some broken parts to show an arm whee the tubing failed first - it's not hard to do. My table is pile a foot deep in electronic parts for my ECU project now so I was too embarrassed to take a picture until I shovel that stuff off to the side a bit.

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PostPosted: June 24, 2015, 11:29 pm 
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wrightcomputing wrote:
3° seems a lot in the rear but if it works it works.


Shims like that can only reduce negative camber, so the upright needs to be designed to cause too much negative camber so that it can be shimmed back to something more reasonable. -3° isn't what he's running, it's the far end of his adjustment range.


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PostPosted: June 25, 2015, 12:55 am 
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mjalaly wrote:
Ummm yeah the bolt thing.... it is installed correctly because the bolt wont go in the other way! its a design issue that i missed. I can alleviate the issue by adding a retention wire or cotter pin in case the bolt loosens. On that note... every bolt and nut should be makred so that during inspection you can tell if they have moved. So many people don't do this!
So that covers the upper bolts...Now what's your excuse for the lowers? :mrgreen:

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PostPosted: June 25, 2015, 7:27 am 
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gregk wrote:
wrightcomputing wrote:
3° seems a lot in the rear but if it works it works.


Shims like that can only reduce negative camber, so the upright needs to be designed to cause too much negative camber so that it can be shimmed back to something more reasonable. -3° isn't what he's running, it's the far end of his adjustment range.

Thanks Greg that makes perfect sense. I was thinking it was adding -ve camber. Up to -3° sounds perfect.

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PostPosted: June 25, 2015, 10:11 am 
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Driven5 wrote:
mjalaly wrote:
Ummm yeah the bolt thing.... it is installed correctly because the bolt wont go in the other way! its a design issue that i missed. I can alleviate the issue by adding a retention wire or cotter pin in case the bolt loosens. On that note... every bolt and nut should be makred so that during inspection you can tell if they have moved. So many people don't do this!
So that covers the upper bolts...Now what's your excuse for the lowers? :mrgreen:


I put them in wrong.... I corrected a while back... that pic is old :cheers:

And BEFORE you look at the new pic... no I didn't have the nut on or tightened in this pic


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Last edited by mjalaly on June 25, 2015, 10:19 am, edited 1 time in total.

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PostPosted: June 25, 2015, 10:15 am 
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gregk wrote:

Shims like that can only reduce negative camber, so the upright needs to be designed to cause too much negative camber so that it can be shimmed back to something more reasonable. -3° isn't what he's running, it's the far end of his adjustment range.


Correct... I will probably end up with something around 2° in the front and 1° in the rear.

I can also machine more off the upright if i need even more... but i doubt it.

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