rdodger
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| posted on 22/11/12 at 07:07 PM |
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Chassis. Which is best and why?
I have been reading the topic about removing a tube in the chassis to fit the engine and it got me thinking about the different chassis designs.
Lotus, Caterham, MK, MNR, MAC#1 etc and the book chassis. They all have similarities, but some are quite different in terms of bracing etc. Round or
square tube?
So... which is best?
Why?
How can they be improved?
What have you done?
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loggyboy
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| posted on 22/11/12 at 07:16 PM |
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String - how long is it?
Mistral Motorsport
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phelpsa
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| posted on 22/11/12 at 07:20 PM |
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Popcorn at the ready 
It depends what you want your car to do. None of them are very good off road.
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RK
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| posted on 22/11/12 at 08:04 PM |
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OK, I'll go! The real answer is "I don't know" but as usual, that won't stop me! Square is easier to weld (apparently),
than round, and makes fitting body work easier. I am fairly certain that as long as the required welding is done, and there are the requisite amounts
of bracing, round is no better than square. I think that the Aussie mods will give you a pretty stiff, safe chassis, so check what that is, exactly
and go from there. I don't see how you can go wrong with it anyways.
I am not an engineer!
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ReMan
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| posted on 22/11/12 at 08:18 PM |
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MK is the best chassis and I should know I've got one
 
Delight
www.plusnine.co.uk
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deezee
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| posted on 22/11/12 at 08:33 PM |
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Lets all guess until the loudest person wins. The Haynes Roadster is the best because science made it with maths and then magic took place and it was
promoted to the finest sports car. More torsional rigidity than a Mclaren F1 and aerodynamically better than a F14 Tomcat.
Hope this helps.
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mookaloid
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| posted on 22/11/12 at 08:54 PM |
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one day it's my ambition to build a live axle striker - or a caterham - either would be at the top of my list for "bestness"
"That thing you're thinking - it wont be that."
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big_l
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| posted on 22/11/12 at 09:28 PM |
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Surely the MNR is right up there the quality is Awsome and very nicely disigned but quality comes with a price tag !!
Check out my blog  mnrvortxhayabusa@blogspot.com
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Talon Motorsport
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| posted on 22/11/12 at 09:55 PM |
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The best chassis is one that does the job that you ask of it at the price that you can afford. And that is probably the most sensible thing I ever
said on here.
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daniel mason
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| posted on 22/11/12 at 09:58 PM |
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after driving loads of sevens. the caterham is by far the best balanced and well sorted. but very very small in comparison to the others mentioned.
could all be down to setup.but it really feels a well sorted chassis!
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JekRankin
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| posted on 22/11/12 at 10:08 PM |
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If I ever decide to own another kit, it'll be a used Caterham. I've discovered that I like well developed components and quality of fit
and finish too much to bother with many of the cheaper kits!
[Edited on 23/11/12 by JekRankin]
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daniel mason
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| posted on 22/11/12 at 10:34 PM |
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my s3 is a tight squeeze. im only 5 10" and 12 1/2 stone.
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hughpinder
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| posted on 23/11/12 at 09:42 AM |
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Ok, I'll also light the blue touchpaper -
Sylva J15, I believe one passed the aussie test unmodified, which I don't think anything else has with a standard chassis (of what I consider to
be a kit - cateringvans are too dear).
If you want the square tube vs round debate in summary - a 25mm *1.5mm square tube has the same nomimal bending strength as a 25mm*1.5 round tube, so
round is better as its would be lighter for the same strength, but a square tube has (4/3.14159...) times the weld area at each join and is easier to
attach panels to and also to make jigs to assemble it accurately, so square is better. A whole chassis in square comes in about 65kg painted, so I
guess a round tube chassis would be 12-15kg less. I wouldn't worry whick it is unless I was racing at the top end where the weight reduction of
round may be worthwhile. (next you should ask if aluminum tube is better or T45....)
DAX cars seem to be nicely made last time I looked properly.
Regards
Hugh
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franky
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| posted on 23/11/12 at 10:00 AM |
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I'd go for anything by Jeremy Phillips or caterham.
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mcerd1
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| posted on 23/11/12 at 10:34 AM |
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quote:
Originally posted by hughpinder
DAX cars seem to be nicely made last time I looked properly.
the chassis is nice 
and they are quite big/wide and the eingine sits a bit further back compaired to some, but they arn't quite as light
they also have quite alot of bracing:
 
Rush Chassis
maybe more bracing than it really needs but I don't think I'd be happy with a RH B2 chassis:
besides the dax must be the best as they are based on german engineering  (started out as a Mohr Rush)
{runs for cover  }
-
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phelpsa
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| posted on 23/11/12 at 11:33 AM |
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quote:
Originally posted by hughpinder
If you want the square tube vs round debate in summary - a 25mm *1.5mm square tube has the same nomimal bending strength as a 25mm*1.5 round tube, so
round is better as its would be lighter for the same strength
IIRC last time I checked you needed 28mm round tube to get the same 2nd moment of area as an equivalent walled 25mm square tube, giving you a weight
saving of 13% for round.
The difference of round vs square is negligible compared to actual chassis design and member placement.
[Edited on 23-11-12 by phelpsa]
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Hellfire
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| posted on 23/11/12 at 01:07 PM |
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Caterham.
Phil
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Alfa145
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| posted on 23/11/12 at 01:43 PM |
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Roadrunner SR2
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umgrybab
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| posted on 25/11/12 at 01:48 PM |
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quote:
Originally posted by phelpsa
quote:
Originally posted by hughpinder
If you want the square tube vs round debate in summary - a 25mm *1.5mm square tube has the same nomimal bending strength as a 25mm*1.5 round tube, so
round is better as its would be lighter for the same strength
IIRC last time I checked you needed 28mm round tube to get the same 2nd moment of area as an equivalent walled 25mm square tube, giving you a weight
saving of 13% for round.
The difference of round vs square is negligible compared to actual chassis design and member placement.
[Edited on 23-11-12 by phelpsa]
I always knew a square tube was way stiffer in bending and I just ran the calcs on this, and for the 25mm square tube with a 1.5mm wall thickness, the
equivalent round tube with a 1.5mm wall thickness would need to be 52.5mm in diameter. This does not answer everything as how often do you have a
member in pure bending? Hopefully never is the correct answer. Like said above, chassis design and member placement is much more important.
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phelpsa
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| posted on 25/11/12 at 07:34 PM |
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quote:
Originally posted by umgrybab
quote:
Originally posted by phelpsa
quote:
Originally posted by hughpinder
If you want the square tube vs round debate in summary - a 25mm *1.5mm square tube has the same nomimal bending strength as a 25mm*1.5 round tube, so
round is better as its would be lighter for the same strength
IIRC last time I checked you needed 28mm round tube to get the same 2nd moment of area as an equivalent walled 25mm square tube, giving you a weight
saving of 13% for round.
The difference of round vs square is negligible compared to actual chassis design and member placement.
[Edited on 23-11-12 by phelpsa]
I always knew a square tube was way stiffer in bending and I just ran the calcs on this, and for the 25mm square tube with a 1.5mm wall thickness, the
equivalent round tube with a 1.5mm wall thickness would need to be 52.5mm in diameter. This does not answer everything as how often do you have a
member in pure bending? Hopefully never is the correct answer. Like said above, chassis design and member placement is much more important.
I've just done the calcs and got 30mm OD for equivalent wall thickness.
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jossey
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| posted on 25/11/12 at 07:49 PM |
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Best chassis is the one you build yourself. :-)
Tiger chassis's are good cos everyone is slightly different lol
Thanks
David Johnson
Building my tiger avon slowly but surely.
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garybee
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| posted on 25/11/12 at 10:14 PM |
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I'm going to go the other way to everyone else and say...NOT a Ginetta G27
It is absolutely awful. It's so bad that I actually had to cut out the section between the rear suspension turrets and weld in something that I
would be happy to bolt my seat belts to (original was simply not safe). As for the rest of it, one day I will give the car a full roll cage and a
proper transmission tunnel to give it some shred of rigidity.
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scootz
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| posted on 27/8/13 at 09:44 PM |
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quote:
Originally posted by garybee
I'm going to go the other way to everyone else and say...NOT a Ginetta G27
It is absolutely awful. It's so bad that I actually had to cut out the section between the rear suspension turrets and weld in something that I
would be happy to bolt my seat belts to (original was simply not safe). As for the rest of it, one day I will give the car a full roll cage and a
proper transmission tunnel to give it some shred of rigidity.
Thread revival - I'm surprised to read that you think the Ginetta chassis is so sloppy as they have a strong heritage of building proper
racecars!
It's Evolution Baby!
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scootz
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| posted on 27/8/13 at 09:46 PM |
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PS - I found this thread when searching for 'torsional rigidity'.
I see the Quantum Xtreme (of which I have a renewed vested interest in) has a torsional stiffness in excess of 4000nm. What would be the norm for a
typical 7-style spaceframe?
It's Evolution Baby!
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britishtrident
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| posted on 27/8/13 at 09:59 PM |
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quote:
Originally posted by umgrybab
I always knew a square tube was way stiffer in bending and I just ran the calcs on this, and for the 25mm square tube with a 1.5mm wall thickness, the
equivalent round tube with a 1.5mm wall thickness would need to be 52.5mm in diameter. This does not answer everything as how often do you have a
member in pure bending? Hopefully never is the correct answer. Like said above, chassis design and member placement is much more important.
I think you need to check the maths again
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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