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Old 13-09-2020, 10:40 AM   #11
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I sincerely hope it's not a street car - I'd not wish to be on the same roads as that suspension. It's a near-perfect example (in terms of engineering/materials loading) of how not to do it. Truly scary - a little knowledge is a dangerous thing...
It was a drag car as is the new one. To be fair, once he was done he could lift the front of the car one handed it was so light.
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Old 23-09-2020, 04:37 PM   #12
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looks similar to the mustang type setups you can buy in the states , abeit narrow version, i have looked at these for my bug to copy. my only comment looks like from the pics only 4 fixing bolts at the bottom? , in close proximity in the center.
i would have had it boxed completely not open nor any lightening holes in the main carrier tho ok for strip use which i think the car does.
i like the look and its a nicely made bit of kit.


im not a suspension guy or engineer so i can only guess he has done all calcs and made it to suit those specs for its purpose.
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Old 23-09-2020, 06:26 PM   #13
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looks similar to the mustang type setups you can buy in the states , abeit narrow version, i have looked at these for my bug to copy. my only comment looks like from the pics only 4 fixing bolts at the bottom? , in close proximity in the center.
i would have had it boxed completely not open nor any lightening holes in the main carrier tho ok for strip use which i think the car does.
i like the look and its a nicely made bit of kit.


im not a suspension guy or engineer so i can only guess he has done all calcs and made it to suit those specs for its purpose.
There are much, much better examples of suspension design online, the trick is learning enough about engineering to spot them. Sadly, '...nicely made...' does not equal nicely designed or fit for purpose. It is extremely unlikely that that the designer had sufficient knowledge to enable a stress analysis, and even more unlikely that it went through destructive testing. Fatigue testing? Forget it... Remember that one's own life and others' are on the line if you get it wrong.

A few golden rules; look at the designs mentioned here and see if they break any or all of them:

1. Never introduce loads into the middle of a tube.
2. Never bend tubing.
3. Never load a fastener in single shear.
4. Never load a safety-critical fastener in single shear.
5. Always think in triangles, tetrahedra, or monocoques - these are the essence of elegant engineering.

Now of course if one takes the NASCAR route and makes everything of proportions more applicable to a railway bridge then nothing will break, but it remains a horribly inelegant, wasteful (of materials), and heavy solution.

Take care, Carl.
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Old 23-09-2020, 08:59 PM   #14
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looks similar to the mustang type setups you can buy in the states , abeit narrow version, i have looked at these for my bug to copy. my only comment looks like from the pics only 4 fixing bolts at the bottom?
Yep, thatís what it reminds me of. Also are the four mount points the same as the stock bug beam?
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Old 23-09-2020, 09:02 PM   #15
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A few golden rules; look at the designs mentioned here and see if they break any or all of them:

1. Never introduce loads into the middle of a tube.
2. Never bend tubing.
3. Never load a fastener in single shear.
4. Never load a safety-critical fastener in single shear.
5. Always think in triangles, tetrahedra, or monocoques - these are the essence of elegant engineering.
Fair points.
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Old 24-09-2020, 08:36 AM   #16
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Yep, thatís what it reminds me of. Also are the four mount points the same as the stock bug beam?
It's like the Americans never moved on from 50's hot rods.
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Old Yesterday, 04:57 PM   #17
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I'm confused, never bend tubing? in all situations or just certain ones?
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Old Yesterday, 06:15 PM   #18
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I'm confused, never bend tubing? in all situations or just certain ones?
In a perfect world, never. Never ever. A bent tube becomes a rather poor spring.

Research 'Euler Column Strength' and 'Euler Buckling Theory' to see how dramatically the stiffness of any structural member, not just hollow members, is reduced when they deviate from being perfectly straight, even by seemingly insignificant amounts. Column strength also varies with the end fixation or condition. (ie. a welded join or a hinged joint at any given end). For example a tube welded into a structure at both ends can withstand a higher force before buckling than than an identical piece of tube with a Rose joint at each end. The slenderness ratio and wall thickness to tube diameter ratio clearly also have dramatic effects on the stiffness and load capacity of a tube whether straight or bent - the latter also known as 'Pre-Failed' in some engineering circles...

Try this revealing experiment: take a paperclip and cut two dead straight pieces out of it as long as possible, and of equal length. Take one of them and put a slight bend in the middle of it over your thumbnail, say 3mm deflection from straight. Place the ends of the straight piece on the pads of your thumb and index finger and try to fold it double simply by pressing square onto the ends. Do the same with the bent piece. It's the same with tubes which would you rather have?

This partly explains why, on true space frames, loads are always fed into the structure at its nodes, and not in the middle of an unsupported tube, which is then placed in a bending mode, rather than pure tension or compression modes which define a space frame.

Check out the engine mounts on this 3/4 ton 1700bhp engine. At 6g that's 4.1/2 tons load shared by those little straight tubes! Aviation engineering is a fantastic source of how to build things light and stiff!
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Old Today, 05:22 PM   #19
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Oh right, ok.
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