ecosse
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| posted on 15/3/07 at 10:34 PM |
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Trailing arms from solid bar
Any reason why not?
Was thinking about using bright bar or silver steel bar to make my trailing arms (maybe 16mm dia?), I reckon I can drill at least 4" in either
side, so weight wise it won't be much more than cds tube (if at all) and it's cheaper 
Any thoughts, daft, pointless, complete overkill, or just use erw and get on with it? 
While I can't come up with a good reason not to, that usually means I have missed something obvious, so does anyone feel like pointing out the
error of my ways to me?
Cheers
Alex
BTW
one end will be rosejointed so it would save making up inserts if nothing else 
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3GEComponents
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| posted on 15/3/07 at 10:50 PM |
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Hi Alex,
Any good engineering tool suppliers can supply drills in long series (5xD even 10xD), so, if you go this route you could drill all the way through.
Remember, all the best driveshafts get gun drilled!
ATB
John
[Edited on 15/3/07 by jroberts]
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flak monkey
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| posted on 15/3/07 at 10:59 PM |
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Just use erw and be done with it! 
David
Sera
http://www.motosera.com
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andyharding
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| posted on 15/3/07 at 10:59 PM |
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Or just use 3/4" ERW tube.
Are you a Mac user or a retard?
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ecosse
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| posted on 15/3/07 at 11:01 PM |
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Yup, fair point, but my lathe might be the limiting factor there John, lets just say it was at the back of the Q when the long beds were getting
handed out
Although I am glad to see no one has any points against to make.
Still not sure why solid bar is cheaper than tube though, more work in making tube I suppose!
No one else done this before? Why don't I believe that
Cheers
Alex
PS
I know drive shafts are generally (always?) hollow, but I don't think I've ever seen a reason why though?
PPS
LOL...you just had to didn't you FM 
Andy too!
[Edited on 15/3/07 by ecosse]
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ecosse
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| posted on 15/3/07 at 11:04 PM |
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Anyway I thought ERW was a no no for trailing arms, not up to the job?
And while we are on the subject (well i am anyway ) does a sierra rear with dedion put more stress on the trailing arms than a live axle or less?
Go on you know you want to tell me
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flak monkey
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| posted on 15/3/07 at 11:05 PM |
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quote:
Originally posted by ecosse
PS
I know drive shafts are generally (always?) hollow, but I don't think I've ever seen a reason why though?
Heres a very brief why for you, because i am off to bed:
Making them hollow obviously reduces their weight, but it also doesnt affect their torque transmitting ability assuming you dotn make them too
thin.
Similarly as with bending, the outside edge of the tube carries most of the torque when applying a twisting moment. So the best way to increase the
torque carrying capacity of a shaft is to increase its outer diameter.
Both bending and torsion calculations take into account the second moment of area (moment of inertia) which increases with the distance of the amount
of mass from the neutral axis of the 'beam'.
That do you?
Dave
[Edited on 15/3/07 by flak monkey]
Sera
http://www.motosera.com
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flak monkey
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| posted on 15/3/07 at 11:09 PM |
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Mine, and all the GTS (along with several other manufacturers) trailing arms are all ERW, more than man enough for the job. Would go for no thinner
than 16g if i were making them, perhaps 14g if you are worried at all.
David
Sera
http://www.motosera.com
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ecosse
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| posted on 15/3/07 at 11:29 PM |
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quote:
Originally posted by flak monkey
That do you?
Dave
[Edited on 15/3/07 by flak monkey]
You just shattered the remnants of my O level applied mechanics knowledge
But thanks anyway 
Alex
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gazza285
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| posted on 15/3/07 at 11:33 PM |
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quote]Originally posted by ecosse
Any reason why not?
Was thinking about using bright bar or silver steel bar to make my trailing arms (maybe 16mm dia?), I reckon I can drill at least 4" in either
side, so weight wise it won't be much more than cds tube (if at all) and it's cheaper
Any thoughts
Don't bother drilling to thread for a male Rose joint, just thread it for a female joint.
No twisting moments are applied through to a trailing arm. Strictly compression and tension my friend.
DO NOT PUT ON KNOB OR BOLLOCKS!
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blakep82
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| posted on 15/3/07 at 11:45 PM |
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I've done mine in solid 1" bar (each one nearly 1 meter long...) and i'm considering re-doing with seamless tube. I'm told
tube is actually less likely to bend. don't know really.
seen some racing cars use aluminium tube for trailing arms. interesting.
________________________
IVA manual link http://www.businesslink.gov.uk/bdotg/action/detail?type=RESOURCES&itemId=1081997083
don't write OT on a new thread title, you're creating the topic, everything you write is very much ON topic!
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ecosse
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| posted on 15/3/07 at 11:57 PM |
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Interesting, if I use a female rose joint I could use thinner bar nice 1 Gazza, that might just be the way to go, some 1/2 bar machined down
for 1/2 unf rose joint.
1" bar a meter long must a be a fair weight although as not on a seven (pickup?) possibly of no consequence?
Cheers guys
Alex
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blakep82
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| posted on 16/3/07 at 12:10 AM |
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trailing links
thats them in orange/white/unpainted. they are heavy, but for suspension i'd prefer to over do it, than have it all fall apart. like you say
though, very heavy so i'll probably re-do them with seamless tube, threaded 5/8" inserts from rally design and 5/8" rose joints. got
1/2" on there, which i'm not happy with. using 5/8" up front you see
here's what i'm doing
________________________
IVA manual link http://www.businesslink.gov.uk/bdotg/action/detail?type=RESOURCES&itemId=1081997083
don't write OT on a new thread title, you're creating the topic, everything you write is very much ON topic!
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gazza285
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| posted on 16/3/07 at 12:17 AM |
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Not sure I'd use as thin as 1/2" though, you still need to stop it flexing under compression. Mine are seamless Hydrolic pipe.
DO NOT PUT ON KNOB OR BOLLOCKS!
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Mal
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| posted on 16/3/07 at 08:05 AM |
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Solid Bar
Don't use silver steel it will harden when you weld it, and may lead to cracking.
My choice would be to buy some cds tube from a local hydraulics company. It is available in various diameters and wall thicknesses.
Mal
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NS Dev
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| posted on 16/3/07 at 08:52 AM |
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Exactly as Mal says, just buy some 3/4" steel hydraulic tubing, cheap enough (certainly cheaper than bar!!!! )
ERW will be fine for trailing arms though.
Retro RWD is the way forward...........automotive fabrication, car restoration, sheetmetal work, engine conversion
retro car restoration and tuning
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gazza285
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| posted on 16/3/07 at 09:10 AM |
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It might harden if you weld it, but why would he be welding it?
DO NOT PUT ON KNOB OR BOLLOCKS!
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12a RX-7
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| posted on 16/3/07 at 01:02 PM |
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trailing arms should not be subject to any (or very little) bending loads anyway. If they are subject to bending they must be binding.
You should be more concerned with the buckling load which is also dependant on the 2nd moment of area of the links rather than the cross sectional
area which is basically what was eluded to above with the bending comment.
Watch out just basing material selection on strength though, how rigid the material is, is also a factor. link are no good if they move and flex under
the load even if they don't break! This is apparent in structures that use chromoly tubes for example, it is strong but the rigidity
doesn't increase that much so the tube will take the load but it will deflect more than a heavier thicker tube.
All the above is only in my opinion and should only be taken as that ... please check it out for yourself before taking any of it as fact LoL
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flak monkey
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| posted on 16/3/07 at 01:45 PM |
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Who said anything about cross sectional area and bending? . I answered a question about driveshafts which was slightly off topic, but still a valid
question. And thats all about second moment of areas (moment of inertia if you like) which comes into all buckling strength, beam stiffness and
torsion calculations.
Once again heavier thicker tubes do not necessarily increase stiffness! They increase the tensile strength of a member.
The advantages of using CrMo tube over mild steel is that it has a much higher strength, so will yeild at a much higher force. There is absolutely no
stiffness variation across any of the steels, regardless of what alloy you care to mention.
David
[Edited on 16/3/07 by flak monkey]
Sera
http://www.motosera.com
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ecosse
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| posted on 16/3/07 at 02:55 PM |
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As per other post, would this stuff, ASTM A106 grade B, cold drawn seamless do the job?
Trailing arms and panhard?
Okay trailing arms seem less important than the panhard but I can get this stuff for a couple of quid a meter so the trailing arms would get a dose of
it as well
Cheers
Alex
[Edited on 16/3/07 by ecosse]
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flak monkey
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| posted on 16/3/07 at 03:08 PM |
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CDS is the standard seamless tube. Will be perfectly ok.
David
Sera
http://www.motosera.com
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ecosse
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| posted on 16/3/07 at 03:28 PM |
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At last, a local supplier at a good price and with the right stuff, I was begining to think it was not possible 
Thanks David (and everyone else too ) much appreciated
Cheers
Alex
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12a RX-7
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| posted on 16/3/07 at 05:30 PM |
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quote:
Originally posted by flak monkey
Who said anything about cross sectional area and bending? . I answered a question about driveshafts which was slightly off topic, but still a valid
question. And thats all about second moment of areas (moment of inertia if you like) which comes into all buckling strength, beam stiffness and
torsion calculations.
Once again heavier thicker tubes do not necessarily increase stiffness! They increase the tensile strength of a member.
The advantages of using CrMo tube over mild steel is that it has a much higher strength, so will yeild at a much higher force. There is absolutely no
stiffness variation across any of the steels, regardless of what alloy you care to mention.
David
[Edited on 16/3/07 by flak monkey]
I think you missed my point.
Reason for using material with higher tensile strength = reduce the section of the material and make it lighter while taking the same loads.
Problem - smaller sections have smaller values for second moment of area and as you said the value for youngs modulus does not change much for any
steel. circa 200GPa
so take for example a beam in simple bending with a point load at it's centre
deflection is given as (PxL^3 ) divided by (48 x Youngs modulus x 2nd moment of area)
I've already said that Youngs modulus can almost be taken as a constant for steels so we can eliminate that for comparison puproses and assuming
we are comparing the same structure the load and the length can be eliminated as well.
so that deflection is inversly proportional to the 2nd moment of area.
(ie. change in deflection for a given structure = 1/I)
SO assuming the only reason to use a higher strenth material is to save weight and all steels are roughly the same density you will probably be
reducing the value of I to to lower the weight and take advantage of the materials higher yield strength.
if you get my point (It's hard to put across in a few words)
[Edited on 16/3/07 by 12a RX-7]
[Edited on 16/3/07 by 12a RX-7]
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flak monkey
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| posted on 16/3/07 at 05:43 PM |
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OK i think I know what you are trying to say. But using a stronger material in a structure of any kind doesnt increase its stiffness, only the load it
can take to failure.
By reducing I you are reducing the bending/torsional STIFFNESS of the beam regardless of what material you use, whether its stronger or not. The
strength of the material you are using doesnt enter into the equation at all until you want to calculate the buckling load.
There is a distinct difference between stiffness and strength.
In short if you want a stiff structure, then you need to use beams with a high second moment of area/polar moment of inertia. The effect of the
strength of these beams has no effect on the overall stiffness of the structure. If you want a strong struture as well you also need to use something
like CrMo steel which has a higher yeild point.
Another point, reducing the second moment of area doesnt necessarily reduce weight. Quite the contrary infact. You can increase the stiffness of a
chassis, and reduce its weight by choosing the right beam sections to use.
David
[Edited on 16/3/07 by flak monkey]
Sera
http://www.motosera.com
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Alex B
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| posted on 16/3/07 at 06:54 PM |
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Alex did you try Hydrasun at Cambuslang . They have seamless hydraulic........was reasonable when I bought from them.
Alex
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