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oh -- I see what you mean.



That is particularly nasty. Like you pointed out there are loads being introduced mid-span on that tube and the tube in front of it. The way that he did this is bad for 3 reasons

1) The trailing arm of the a-arm will get compression loads going through it during acceleration, and more importantly during cornering, and there is nothing behind that point to take these compression loads. To a lesser degree there will be tension loads on that point during braking.

2) Even nastier is that he attached the bracket holding the a-arm pivots by a bolt through the tube. So right there he's taken away at least a 3rd of the tube's strength by drilling a hole in it. He's also compromised the tube by putting compression forces on the diameter of the tube, which can cause the tube to flatten after the bolt is tightened, weakening the tube even more.

3) If you are going to attach something by bolting it, the bolt needs to be in double-sheer, or in extreme situations single-sheer with a larger bolt.

If he tries to drive that car in anger, it's quite likely that those tubes holding the rear suspension will fail, with potentially catastrophic consequences if it occurs at speed. If you look at this picture of a real 917/10's rear suspension you can see that the rear upper "a-arm" is really a trailing link from the bulkhead which is loaded in compression/tension under acceleration and braking, and a lateral link that goes to a mount at a junction of tubes (although it is not real clear in the image) that handles the lateral loads.



Here's a close up from what I think is a 906 chassis of where the lateral link ties into a frame bracket. The point in question is in the center of the image. I'm pretty sure that the execution was pretty much the same on all of Porsche's tube-frame chassis prototype chassis.



Note how it is boxed in, and tied to the "bulkhead" tube in the background that goes to the other side of the chassis. Also note that the bolt through the lateral link's rod-end is supported on both-ends of the rod-end by the bracket. While not perfect or elegant, it's a far superior design.
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Last edited by jluetjen; 10-03-2011 at 08:23 AM..
Old 10-03-2011, 08:16 AM
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Hats off to this fellows project. Others need to chill on this board as this is just ones idea that he's obviously proud of and enjoys Porsches... like all of us. Good for him. Done right or wrong, I hope he accomplishes it.

I'm not going into what should be done or whatever but thought I'd share some pics I took of this icon. All of you experts should recognize this aluminum chassis with titanium springs, mag crankcases, yada, yada. By the way, the chassis was pressurized with gas to detect any cracks or fractures (and no, it wasn't helium to make it any lighter... 93lbs ; )

Cheers, Scott









Old 10-03-2011, 09:11 AM
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Originally Posted by jluetjen View Post
oh -- I see what you mean....

That is particularly nasty.
I think you get my point now. There is no sound engineering in that chassis and not even any decent redneck engineering. It's potentially hazardous to anybody that drives it. It make you wonder what other choices he made in tubing size/alloy, in how the engines are bolted together and a bunch of other things. The sad thing is the guy spent a lot of time, and probably a fair bit of money, and the end product is grossly flawed. A little guidance from a pro, or a weekend spent reading the endless books available to armchair race engineers, or to the experimental aircraft crowd, would have resulted in something that could have been used and enjoyed.

I'm not trying to knock the guy just for the hell of it.

JR

Last edited by javadog; 10-03-2011 at 09:16 AM..
Old 10-03-2011, 09:14 AM
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Hats off to this fellows project. Others need to chill on this board as this is just ones idea that he's obviously proud of and enjoys Porsches... like all of us. Good for him. Done right or wrong, I hope he accomplishes it.
Hat's off to this guy's enthusiasm but he intends to sell the car, if I heard him correctly in his video. I'm a little concerned for the future owner.

Not that I have a dog in this fight...

JR
Old 10-03-2011, 09:19 AM
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I think you get my point now. There is no sound engineering in that chassis and not even any decent redneck engineering. It's potentially hazardous to anybody that drives it. It make you wonder what other choices he made in tubing size/alloy, in how the engines are bolted together and a bunch of other things. The sad thing is the guy spent a lot of time, and probably a fair bit of money, and the end product is grossly flawed. A little guidance from a pro, or a weekend spent reading the endless books available to armchair race engineers, or to the experimental aircraft crowd, would have resulted in something that could have been used and enjoyed.

I'm not trying to knock the guy just for the hell of it.

JR

OK, I see what your talking about. I didn't even notice at first. I looked at pictures of race cars I have owned and they all have a common theme to suspension mounting. This car should be easy enough to fix though.
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Old 10-03-2011, 09:32 AM
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For example, a fairly simple (but kludgy) solution would be to make diagonals from where the through-bolts are for the A-arm up to a central point under the oil cooler. He'd also need to re-engineer the way that the bolts attach to the frame there by cutting the tube and welding in a short tube going through frame tube, which would be bushed for the bolt. So basically rather than 1 longer tube with a bolt hole in it, it would be two tube welded to short tube mounted 90 degrees from the longer tube (pointed to the center of the car. Weld the diagonal to that short tube for the through-bolt. Kind of like this...



I've also drawn in one of the left side tubes.
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Old 10-03-2011, 11:15 AM
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No worries it looks better then mine.........I still give him a "A"
most here can not weld let a lone make , loft, scale, fabricate, spile, locate.
He is doing GREAT !
Old 10-18-2011, 08:36 AM
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Old 10-18-2011, 07:08 PM
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I've been following this. and while I do respect what he's doing.............

in my view it means more to do a less ambitious project very well than a more ambitious project poorly.

if he is looking to sell it in the future, a prospective purchaser would be more impressed with a high quality job than one with obvious failings. the flaws are going to leap out at him. the person that would be interested in a car like this won't be able to live with the obvious issues. which means going back in and fixing them.

IMHO.
Old 10-18-2011, 08:27 PM
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I have been a welder for yrs. I would rather see a hot messy weld then a cold weld..
Lots a stuff here criticized will never break. It could be dropped 5 feet....will bend but not fail.
Most here,= and I do mean MOST have never welded pipe or tube. It is quite the challenge for the person doing it the first time.
Even when lots a pros get done its ground to smooth and pretty. Looks like he skiped that part. No big deal.
The only prob I see is the rear upper "A" frame brackets. I have no clue what Porsche did there..
..Looks a tad wrong...but a EZ fix.
If one looks around in the back ground there they will see lots of other cars.....my guess is he will work it all out.
Hats off to him.!
Old 10-19-2011, 03:15 AM
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Has anyone with the knowledge of what is wrong tried contacting this guy? Seems like a pretty cool and down to earth 'car-guy' to me. That would be the obvious step.
Old 10-19-2011, 07:30 AM
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I have been a welder for yrs. I would rather see a hot messy weld then a cold weld..
Lots a stuff here criticized will never break. Most here,= and I do mean MOST have never welded pipe or tube. It is quite the challenge for the person doing it the first time.
Even when lots a pros get done its ground to smooth and pretty. Looks like he skiped that part. No big deal.

Afterburn, glad you put that out there. I'm always amazed at many of the critical points made on this forum by those who have only... well, read about it, or "heard from a friend who," or knows somebody that did, etc.. yet posses no real world hands on experience with the the activity at hand!

I'm just say'n..
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Old 10-19-2011, 11:12 AM
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I agree with Haycait911. Seems this guy could have built an amazing Super7 instead of a 'questionable' 917. Then again maybe he already has...


I do find the difference in tone between this thread and the Beck 904 threads interesting. Maybe the purists are still making their way back from Rennsport?

Not that I am a purist. I am not against kit cars, I just dont exactly see what direction he's going for. There is some very nice attention to detail coupled with some odd choices. The slushbox in particular kills it for me. It would be cool to see it on the street though. Hope it all comes together for him.
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Old 10-19-2011, 11:46 AM
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Thanks jluetjen. It was like doing the Rubik's cube with my elbows. You have to be able to think in three dimensions when designing the car so everything works and can be maintained.
Old 10-15-2017, 02:42 PM
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You have to take your hat off to this guy, the creative problem solving to building this on a budget and fabrication effort is pretty incredible!





I really wish I had the ability to do something like this for a 906 replica.
Thanks jluetjen. It was like doing the Rubik's cube with my elbows. You have to be able to think in three dimensions when designing the cars so everything works and can be maintained.
Old 10-15-2017, 02:44 PM
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This should be interesting to see come together... excellent fabrication skills, wonder what he does full time?
Thanks onboost. I'm 66 and was in construction all my life. I spent the last 18 years of my career supervising commercial construction. I'm a MacGyver type. I like to build things and take on projects.

Jack
Old 10-15-2017, 02:48 PM
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Corvette suspension and brakes? Two Subaru engines bolted together? Its an interesting thing he's created, but I certainly wouldn't call it a 917 replica.
What would You call it? Is there another 917 replica out there with a 12 cylinder Boxer engine and that has the Details MY car does?
Old 10-15-2017, 02:51 PM
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Automatic?!?
I installed the automatic because it came with the engine so therefore, it would work with the engine. I would have had to figure out how to shift a manual with it's controls on the left side of the box from the right side of the cockpit.

I had to design Every part of this car. I did Everything myself. I didn't want to take on another mystery to figure out. I knew there were companies that made controllers for autos but later found out no one made one for this box.

I found out how to do the shifter and cables so I put in a 5 speed box with Tilton pedals.
Old 10-15-2017, 02:57 PM
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"I am hoping to have it all done and auctioned off by the end of the year"
I am on the 8th electrician and third computer company that Said They Could Do IT! It took 7 years for a company to make a computer that I Know can run these engines. I also have found an electrician that sounds like he can wire it.

When you have to depend on Other people to do what they say they can, you had better not hold your breath.
Old 10-15-2017, 03:01 PM
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Certainly a lot of hard work, clean work, and ingenuity involved. But I'm a little less fond of guys who point out their own craftsmanship.




To each his own. For him, I guess it's the journey, not the end product.
If people don't point out their accomplishments, no one will do it for them. Also, no one would be sharing Their creations, so it would be a boring world. I thought That was what we are supposed to be doing here.

Have an Accomplishments You want to share? I, won't think less of You for doing it.
Old 10-15-2017, 03:05 PM
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