Louis M
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| posted on 3/6/04 at 06:29 PM |
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Thicker Steel?
Wouldn't thicker steel make a stronger chassis? Also, it 12swg, 8swg or 4swg able to be arc welded? I'm trying to get a sense of all the
welding equiptment b/c i'm gonna learn on this one... anyway is this too thick for mig, or... i really don't know what i'm talking
about  simply put: can i arc weld 12, 8 or 4? and would this make the chassis stronger?
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Chris_R
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| posted on 3/6/04 at 06:53 PM |
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Thicker steel will make a stronger chassis, but it'll also make it very much heavier. Check previous posts about chassis strength and
you'll find the suggestion that it's better to add more cross braces than to increase wall thickness, if it is strength that you're
looking for.
If your decision to ark weld is motivated by cost, you'll prolly find that, although initially the equipment is cheaper, you will spend more on
consumables and spend more time cleaning up your welds. There are some decent MIG's available for little more than the cost of a stick welder
and you'll find it easier to learn using a MIG.
The thread I was refering to is at http://locostbuilders.co.uk/viewthread.php?tid=1738
[Edited on 3/6/04 by Chris_R]
A bit of slapstick never hurt anyone.
http://www.chris.renney.dsl.pipex.com/
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Mark Allanson
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| posted on 3/6/04 at 08:02 PM |
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You can weld 16g with an arc welder, but it is a bit of a skill - it is much easier with a DC inverter. Use 2.5mm Satinex 6013 rods and the slag will
just fall of a good weld. These rods produce a near perfect 45 degree flat fillet and significantly stronger than mig, and prettier.
If you can keep you head, whilst all others around you are losing theirs, you are not fully aware of the situation
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Louis M
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| posted on 3/6/04 at 09:26 PM |
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cost is an issue, but not really a big one... i've always thought that arc welds are supposidely the best looking out of all the welds, so...
also, since the book is 1" and that holds around 300hp (i believe thats the largest i've heard of), what would 1.5" hold?, i'd
say its around 625hp? (1x1=1, 1.5x1.5=2.25)
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JoelP
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| posted on 3/6/04 at 09:33 PM |
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i dont think the relationship is that linear. Plus one gentleman has been running 460bhp in his own chassis, though i dont know how similar to the
book it is.
i would concentrate on understanding the chassis, and work out where the strength is needed.
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blueshift
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| posted on 3/6/04 at 09:57 PM |
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Alternatively wheedle cymtriks into understanding the chassis for you and answering all the important questions
*gives cymtriks a hug*
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stephen_gusterson
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| posted on 3/6/04 at 10:06 PM |
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I know next to bugger all about welding, but what I do know is arc welding is basically shorting bits of rod on the work. Gives lots of slag and a
roughth looking result.
On the other hand, mig if used right, gives a pretty weld, and tig a thing of beauty.
Building a car is an expensive process, of which buying a hobby mig isnt a massive cost when set against the total. On the other hand, if you build a
crap chassis from the start, your whole car may be trash.
atb
steve
quote:
Originally posted by Louis M
cost is an issue, but not really a big one... i've always thought that arc welds are supposidely the best looking out of all the welds, so...
also, since the book is 1" and that holds around 300hp (i believe thats the largest i've heard of), what would 1.5" hold?, i'd
say its around 625hp? (1x1=1, 1.5x1.5=2.25)
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Mark Allanson
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| posted on 3/6/04 at 10:20 PM |
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Steve, arc welding produces the finest, cleanest weld of all
If you can keep you head, whilst all others around you are losing theirs, you are not fully aware of the situation
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Hugh Paterson
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| posted on 3/6/04 at 10:41 PM |
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Steve, arc welding is far superior than Mig
in the hands of someone that knows what there doing. But it is unusual for someone to choose to use that method on thin walled tube with the
availability of cheap mig equipment
Shug
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crbrlfrost
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| posted on 3/6/04 at 10:47 PM |
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Seems to me that the "cleanest" weld would be produced by a TIG process due to a lack of flux coatings or inclusions. I'm cetainly
not a elding master, but can hold my own most of the time. Not meaning to trample on arc welding, especially on thicker material where nothing else
would do the trick, and in the right hands does produce a beautiful weld. But to each their own. Afterall, we're just talking about
"casting in place!" Cheers!
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Hugh Paterson
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| posted on 3/6/04 at 11:23 PM |
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Yup each to their own, Not everyone has the patience for Tig, I think the attraction with Mig is its a pull of a trigger, if u can master the settings
and get the torch in the right position its fast n clean. Gimme Tig any day though.
Shug.
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rash
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| posted on 4/6/04 at 05:48 PM |
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i used 25x25x3 box section for the chassis and arc welded it its still not going to weigh as much as an escort or sierra if your not racing i dont see
the point in cutting everything back to the bone?
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stephen_gusterson
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| posted on 4/6/04 at 06:30 PM |
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told you I knew nothing.
Am I understanding that is the type where you dab a rod against the work, and basically create sparks?
atb
steve
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Alan B
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| posted on 4/6/04 at 07:19 PM |
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Correct Steve.
Obviously a little more to it than that, but that is basically it.
Louis, yes thicker wall tube is stronger, but it is a very inefficient way of adding strength. If strength and stiffness is a worry then increasing
the section is a FAR better return on the weight increase than increasing the wall thickness.
But, of course that would involve significant re-design.
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crbrlfrost
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| posted on 4/6/04 at 10:24 PM |
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I wouldn't exactly describe the typical locost as "cut to the bone." They are typically light weight, but could be more so if you
tried. Besides, light weight contributes to better accel, braking, and fuel economy (which is one I'm feeling right now). Cheers!
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stephen_gusterson
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| posted on 4/6/04 at 10:31 PM |
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I would....
what else could you leave out and still make a4 wheeled car?
atb
steve
quote:
Originally posted by crbrlfrost
I wouldn't exactly describe the typical locost as "cut to the bone." They are typically light weight, but could be more so if you
tried. Besides, light weight contributes to better accel, braking, and fuel economy (which is one I'm feeling right now). Cheers!
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Louis M
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| posted on 5/6/04 at 02:58 AM |
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quote:
Originally posted by Alan B
Correct Steve.
Obviously a little more to it than that, but that is basically it.
Louis, yes thicker wall tube is stronger, but it is a very inefficient way of adding strength. If strength and stiffness is a worry then increasing
the section is a FAR better return on the weight increase than increasing the wall thickness.
But, of course that would involve significant re-design.
two questions:
1) using cymantic's advise on where to add more pieces, then what else can i do?
2) using what rchapman said, the chassis weighs about 40 lbs when fully complete... assuming i went w/ 1.5", then the total weight would be 60
lbs, which i would be willing (i want to save weight but i'm not going to care about 20 lbs here and there) to give up (i got this by saying
that a 1x1 piece has a total of 4" circum. while a 1.5x1.5 piece has a total of 6" circum... so therefore the weight shouldn't be
THAT large
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Cita
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| posted on 5/6/04 at 06:31 AM |
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Hi Louis,
it all depends on what you gonna use the car for.If it's just day to day driving than i wouldn't care much about a few pounds extra weigth
but bare in mind that weigth adds up quickly!
If you're not an expert welder,like most of us!,than going for thicker wall section will probably ease the job of welding and will add a little
strenght without redesigning the whole frame as you should with larger section tubing.
From what i have been reading though the book frame is plenty strong.
good luck!
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flak monkey
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| posted on 5/6/04 at 06:49 AM |
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Louis M
The weight given in the book of 40lb is very wrong! The whole chassis weighs more like 90kg, 180lb! That chassis he is holding up is aluminium,
I'd like to see yu try it with a steel one.
I have a mechanics exam this morning, if not i would sit and work out what steel you would need to make your chassis out of. I would say (without
doing any maths) that 1"x1"x3mm would be strong enough, with extra bracing. Though I cant do FEA....
Attached is a pic of the book chassis wieght, complete with extra bracing, wishbones, a steel transmission tunnel (no tubes just 16g steel!), this was
modelled in CAD. Just so you dont get you hopes up for being able to pick it up when its finished 
Cheers,
David.gif)
Sera
http://www.motosera.com
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Cita
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| posted on 5/6/04 at 07:31 AM |
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The best of luck with your exam!!!
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flak monkey
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| posted on 5/6/04 at 07:33 AM |
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Thanks Cita 
Sera
http://www.motosera.com
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JoelP
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| posted on 5/6/04 at 08:41 AM |
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the weakest area in my humble opinion in a book chassis is the point at the bottom of the scuttle, where the sides kink inwards without any
triangulation. if i did one i would be tempted to straighten the sides out, and make them slope gradually inwards along their total length, rather
than being parallel at the back.
3mm sounds like overkill to me, surely that would double the weight of the chassis? isnt 16g about 1.5m?
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rash
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| posted on 5/6/04 at 04:40 PM |
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i cant understand this big obsession with weight saving the biggest saving i can see is the drivers own bodyweight or maybe its just me not thinking
along the same lines as everyone???
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Mark Allanson
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| posted on 5/6/04 at 05:15 PM |
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The additional work using 1/8" steel would be very time consuming. All the welded faces would have to be bevelled or you would have about 1
1/16" penetration, - that would give you a chassis twice as heavy and the same strength, but with awful stress risers on the reverse side of
every weld. I know you could turn up the amps to compensate, but then you would have very high profile welds compared to the cross section of the
tubes used.
If you can keep you head, whilst all others around you are losing theirs, you are not fully aware of the situation
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britishtrident
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| posted on 5/6/04 at 07:52 PM |
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quote:
Originally posted by flak monkey
Louis M
The weight given in the book of 40lb is very wrong! The whole chassis weighs more like 90kg, 180lb! That chassis he is holding up is aluminium,
I'd like to see yu try it with a steel one.
I have a mechanics exam this morning, if not i would sit and work out what steel you would need to make your chassis out of. I would say (without
doing any maths) that 1"x1"x3mm would be strong enough, with extra bracing. Though I cant do FEA....
Attached is a pic of the book chassis wieght, complete with extra bracing, wishbones, a steel transmission tunnel (no tubes just 16g steel!), this was
modelled in CAD. Just so you dont get you hopes up for being able to pick it up when its finished
Cheers,
David
Original Lotus 7 S2 Chassis weighs about 40 pounds --- but it was 1.2 mm round tube and a very sparse space frame.
Unpaneled bare book chassis without seatbelt mounts rack and engine mounts is about 75 pounds, mine is creeping towards 90 because of lots extra
diagonal bracing.
1.5 or 1.6 mm is easy to weld with MIG and it has one hidden advantage over thicker steel in the hands of a novice welder --- any deffects in welds
are much more likely to be visible not hidden sub surface.
1.5/1.6 also cuts very easily -- 1.2 needs very fine pitch blades while anything thicker is a lot more work.
[Edited on 5/6/04 by britishtrident]
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