JonBowden
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| posted on 20/5/07 at 11:16 AM |
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Thanks folks. I haven't had a chance to have a good look but using rollers seems to be the way to go.
I have a few ideas I'd like to make one day. Using curved tubes might solve some issues.
Jon
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#Rotor
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| posted on 20/5/07 at 05:30 PM |
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our very first practice.....It was her first taste of racing and she loved it...
here are some of the pictures taken at Zwartkops Int.
She ran very very well, I was most impressed with her manners all round the track. pity about the rod-end failure that ruined an otherwhisely perfect
practice.
[Edited on 13/9/07 by #Rotor]
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geoffreyh
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| posted on 20/5/07 at 07:20 PM |
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Is it just the front shield or is it the whole car which is lower at his right side?
It looks really good. What was the problem you've written about?
Do you have some engine specs?
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kb58
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| posted on 20/5/07 at 11:19 PM |
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Now come on, we're all brothers here, you have to share the bad with the good; it's the only way we learn as a group. If you won't
share the video, a detailed explanation, with pictures, is expected!
That aside, was this the car's first outing... because it's really not a good idea to risk two people's lives when finding out if
something's going to break, at least for the initial shakedown tests. Don't pull a Mcbearen on me!
[Edited on 5/20/07 by kb58]
Mid-engine Locost - http://www.midlana.com
And the book - http://www.lulu.com/shop/kurt-bilinski/midlana/paperback/product-21330662.html
Kimini - a tube-frame, carbon shell, Honda Prelude VTEC mid-engine Mini: http://www.kimini.com
And its book -
http://www.lulu.com/shop/kurt-bilinski/kimini-how-to-design-and-build-a-mid-engine-sports-car-from-scratch/paperback/product-4858803.html
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#Rotor
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| posted on 21/5/07 at 06:46 AM |
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we have been driving the car for almost a week, so no not it's very first steps, but first real workout, I was more concerned with roadholding,
and engine reliability, than with a failure like this.
[Edited on 13/9/07 by #Rotor]
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kb58
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| posted on 21/5/07 at 01:44 PM |
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There HAS to be a large bending load applied to cause this. I'll have to go back and look at your suspension design to see what's going
on. This particular part looks like a one-time catastrophic failure, due to the granularity of the material. A stress failure OTOH has tiny beach
marks, like tree rings, part way across the shaft.
One sure way this can happen is if the rod-end was forced to move outside it's design range. It jams the shaft against the ball race, then
applies massive bending load. After it's all back together, I suggest moving the suspension through its full range of travel (without the shock
travel limit pads in place.) There's a very good chance that in a turn, a rod-end was already near its limit of motion, then you hit a bump
which forced the rod-end to jam the shaft against the bearing race. Carefully inspect all the broken rod-ends to see if any has a dent in the edge of
the bearing race.
Like you say, finding what happened first can be tough if the ensuing damage causes secondary failures. OTOH, if a defective rod-end was installed,
yeah, you're pretty much screwed. At least no one was hurt!
BTW, are those aluminum or steel rod-ends?
[Edited on 5/21/07 by kb58]
Mid-engine Locost - http://www.midlana.com
And the book - http://www.lulu.com/shop/kurt-bilinski/midlana/paperback/product-21330662.html
Kimini - a tube-frame, carbon shell, Honda Prelude VTEC mid-engine Mini: http://www.kimini.com
And its book -
http://www.lulu.com/shop/kurt-bilinski/kimini-how-to-design-and-build-a-mid-engine-sports-car-from-scratch/paperback/product-4858803.html
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#Rotor
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| posted on 21/5/07 at 02:42 PM |
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these are normal steel ones. We are actually now in the process of getting some proper Chromoly rod-ends...... 5 times as strong as these,
I did exactly that, and the joint that failed, could have been flexing the rod-end yes, That is the only explanation I can come up with, for it to
have failed.... other than just being a Dud, which with my luck, is also a possibly...
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kb58
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| posted on 21/5/07 at 02:52 PM |
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I just realized something else. Not only are you applying heavy suspension loads for the first time (at the track) but with a passenger, it's
going to move the suspension toward the ends of its range. Between the high cornering loads, a passenger, and hitting a bump, I'm guess that a
rod-end went beyond its limit. Or, like you said, you received a defective part. Are they high quality parts, like $25US apiece? There are some
low-priced ones on the market that are really bad.
Oh and it doesn't matter if you get really high quality rod-ends if you run them outside their motion limits, but you already know that.
[Edited on 5/21/07 by kb58]
Mid-engine Locost - http://www.midlana.com
And the book - http://www.lulu.com/shop/kurt-bilinski/midlana/paperback/product-21330662.html
Kimini - a tube-frame, carbon shell, Honda Prelude VTEC mid-engine Mini: http://www.kimini.com
And its book -
http://www.lulu.com/shop/kurt-bilinski/kimini-how-to-design-and-build-a-mid-engine-sports-car-from-scratch/paperback/product-4858803.html
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#Rotor
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| posted on 21/5/07 at 04:01 PM |
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I would not say they where cheap, but most definitely not extremely expensive,
obviously one should not flex a rod-end, that will make even the most expensive ones snap like a twig, no..... I just want to eliminate as much
potential for product failure.
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Fred W B
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| posted on 21/5/07 at 05:46 PM |
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Hi Rotor
Nice to see the car on the move. Re the rod ends, Some discussion here
atom rod ends
Cheers
Fred W B
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kb58
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| posted on 21/5/07 at 06:19 PM |
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Thanks for the link, Fred, very interesting.
If the rod-end is used purely to push and pull, as it should, I can't understand how that can happen. OTOH, if there's any bending load,
that's a different story. Maybe, and it's a big maybe, if the rod-end's not lined up perfectly with the forces involved, that could
do it. What I mean is, if the threaded portion of the rod isn't lined up with the centerline of the tube, then bending loads will affect it
right at the end of the stop-nut, which is what happened. Hmmmm.
[Edited on 5/21/07 by kb58]
Mid-engine Locost - http://www.midlana.com
And the book - http://www.lulu.com/shop/kurt-bilinski/midlana/paperback/product-21330662.html
Kimini - a tube-frame, carbon shell, Honda Prelude VTEC mid-engine Mini: http://www.kimini.com
And its book -
http://www.lulu.com/shop/kurt-bilinski/kimini-how-to-design-and-build-a-mid-engine-sports-car-from-scratch/paperback/product-4858803.html
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Chris Clarke
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| posted on 21/5/07 at 11:04 PM |
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Looks like a cast rod end housing to me. Even some of the industrial stuff (ie cheap) that we get from China is machined from round stock.
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Alan B
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| posted on 22/5/07 at 01:40 PM |
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Looks like a classic brittle failure to me....as kb says no evidence of beach marks to suggest fatigue.
That, along with the observation of no significant impact, would lead me to suggest poor material...either cast iron (which it does have a look of) or
improper heat treatment..insufficient temper and therefore too brittle.
Just IMO of course.
Alan B
[Edited on 22/5/07 by Alan B]
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#Rotor
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| posted on 24/5/07 at 04:31 PM |
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here I am building the new A-arms for the Rod-ends we are going to be using now, which will be Chromoly 1/2" and won't fit the existing
thread.
[Edited on 13/9/07 by #Rotor]
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kb58
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| posted on 24/5/07 at 05:08 PM |
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quote:
Originally posted by Alan B
Looks like a classic brittle failure to me....as kb says no evidence of beach marks to suggest fatigue.
That, along with the observation of no significant impact, would lead me to suggest poor material...either cast iron (which it does have a look of) or
improper heat treatment..insufficient temper and therefore too brittle.
Just IMO of course.
Alan B
[Edited on 22/5/07 by Alan B]
What's bugging me is that even if it's brittle, how can a rod-end fail in pure tension or compression. I can't help but wonder if it
got bent somehow; the classis reason being that the spherical bearing ran out of travel. OTOH, knowing how it's used, I can't see that
happening. It's strange that the "real" Atom has trouble in this same area. Have you calculated the compression/tension force in the
push/pull rod. I bet it's really high, but even smallish rod-ends are really strong. Pretty odd.
Mid-engine Locost - http://www.midlana.com
And the book - http://www.lulu.com/shop/kurt-bilinski/midlana/paperback/product-21330662.html
Kimini - a tube-frame, carbon shell, Honda Prelude VTEC mid-engine Mini: http://www.kimini.com
And its book -
http://www.lulu.com/shop/kurt-bilinski/kimini-how-to-design-and-build-a-mid-engine-sports-car-from-scratch/paperback/product-4858803.html
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gottabedone
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| posted on 27/5/07 at 04:50 PM |
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what would the fracture look like if the spherical part of the rod end was bottomed out and then the rod end was subjected to a further twisting load
along its length? i.e. transition from acceleration to braking etc
Steve
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#Rotor
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| posted on 27/5/07 at 06:29 PM |
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the more I think about these rod-end, the more I seem to start to realize, these where mighty expensive cheap shit...... pardon my French.
and by expensive, I am actually importing some Chromoly rod-ends, from the states at about 80% the cost of what I paid for these locally.... I can go
for the Kevlar lined Heims, with the same Chromoly body, but it's not the lining that is my problem, so I went for the normal ones in stead.
Will Probably have them Kevlar ones as an BLING option, for those customers. 
bin busy though, got done with all the suspension arms.... here is the rear arms, nicely welded up.
[Edited on 13/9/07 by #Rotor]
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thomas4age
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| posted on 28/5/07 at 01:44 PM |
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Intersting on the rod-ends are those the same as spherical bearings? (the names confuse me because english is not native to me)
the kit I'm currently looking into specifies enourmously expensive SKF Ampep series ones that cost 55pounds each, but the manufacturer of the
kit stated that he would dare to drive another car without these specific ones fitted?
any lead to the question Why?
grtz Thomas
edit: nice welding btw looks strong.
[Edited on 28/5/07 by thomas4age]
If Lucas made guns, Wars wouldn't start either.
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#Rotor
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| posted on 28/5/07 at 05:48 PM |
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quote:
Originally posted by thomas4age
Intersting on the rod-ends are those the same as spherical bearings? (the names confuse me because english is not native to me)
the kit I'm currently looking into specifies enourmously expensive SKF Ampep series ones that cost 55pounds each, but the manufacturer of the
kit stated that he would dare to drive another car without these specific ones fitted?
any lead to the question Why?
grtz Thomas
edit: nice welding btw looks strong.
[Edited on 28/5/07 by thomas4age]
a rodend is basically a spherical bearing in a housing that can be screwed into or over a rod's end, from there the name
"rodend"
I'm getting some shipped from QS Components, they have some seriously awesome stuff ...
http://stores.ebay.com/QS-Components_W0QQcolZ2QQdirZQ2d1QQfclZ3QQfsubZQ2d33QQftidZ2QQtZkm
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..::Nightfire::..
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| posted on 31/5/07 at 06:35 PM |
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Are they instead of brakes? 
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JoelP
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| posted on 31/5/07 at 06:50 PM |
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ive long loved the idea of moveable aerofoils - no drag on the straights and extra grip and braking into the corners. Great idea!
How well do you think the ecu will control it? Will it be able to sense forces or just work out what to do from engine inputs?
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#Rotor
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| posted on 31/5/07 at 07:06 PM |
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I don't know yet, The ECU has a couple of PWM GPO channels, hopefully I will be able to rig it up to work, else I will just build a little servo
driver for it, that will probably sense speed and brakes, and then from that alter the pitch accordingly, for instance, apply full tilt the moment
you touch the brakes, then gradually pull the wing back down, as the speed increases, or something like that....
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JoelP
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| posted on 31/5/07 at 07:09 PM |
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Theres several ways it could be done, from manual via a lever to getting a simple chip linked to a G meter. Might be an idea to link in a rear spoiler
too though, to maintain balance.
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..::Nightfire::..
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| posted on 31/5/07 at 10:25 PM |
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Try hooking it up to a pair of triple axis accelerometers. That combined with a speed sensor on each wheel will give the computer more than enough
information to work out when to apply force.
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#Rotor
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| posted on 1/6/07 at 05:34 AM |
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hell yeah.... I can even have them individaully controlled.... like up the inside side wing when turning........
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