Board logo

Coolant through chassis
coyoteboy - 30/8/10 at 03:23 PM

So in my planning of chassis design I'm considering using a pair, maybe 4 fairly thin-wall ~2" tubes as the main structure (a little atom-esque in a sense) and so the thought came to me that it would make sense to use these to reduce my packaging problems (I believe lotus had a similar idea a while back) and route coolant round the lower set and charge air through the other set. Seeing as I don't expect to see materially significant temps in either route (100Cish max) I'm guessing my only real problems will come from corrosion in the coolant run (minimised by use of decent coolant) and possibly scalding on an impact but that's possible with flexible hoses too.

I'm sure others have attempted this, so does anyone have any links to evidence regarding the extend of the problems with corrosion?

designer - 30/8/10 at 03:41 PM

It's a good idea, been done many times. Coolant should have antifreeze/inhibitor all the time anyway.

BUT, is it OK for SVA?

coyoteboy - 30/8/10 at 03:44 PM

Can't imagine why the IVA would have a problem with how you route your coolant. though I suppose they could be worried about invisible corrosion problems weakening the main members, fair point. Maybe it'd have to be lined with a flexible hose instead, but that adds weight and pointless leak possibilities.

MikeR - 30/8/10 at 04:32 PM

Its banned in motorsport - its a good idea but you can't tell how much the chassis tube is rusting till .... it rusts through. Hence they banned it on safety grounds (or something like that).

iank - 30/8/10 at 06:04 PM

Also an otherwise minor shunt can crack a tube and spray boiling water onto the driver.

The Lotus 23 was one of the first to use it - typical Colin Chapman type of idea to save weight.

bi22le - 30/8/10 at 06:21 PM

Please forgive my stupidity but unless you have the engine at one end and the rad with good air flow at the other why bother?

Also surely (if that is the case) it would be better to keep the rad in the same area as the engine to keep the pipework short. This would then cut down the amount of water needed to fill your cooling system and probably save you weight!?!

coyoteboy - 30/8/10 at 07:28 PM

quote:
Please forgive my stupidity but unless you have the engine at one end and the rad with good air flow at the other why bother?


That's my plan.
quote:

Also surely (if that is the case) it would be better to keep the rad in the same area as the engine to keep the pipework short. This would then cut down the amount of water needed to fill your cooling system and probably save you weight!?!


Loads less weight. OK, maybe 3 or 4kg. But evenly distributed across the car, not all lumped around the back with the car engine and box which already weigh a lot. Not having to be packaged with special ducting to deal with the fact that it's in my "shadow", or placed high, and providing free heating down the passenger tunnel.

While I'd originally mentally played down the thought of a cracked tube scalding me, I then considered possible passengers and think it might be an unpleasantry for them. However any hose can be, and very easily are, severed in a small shunt, so I'm not sure it's much different. Other than the rust issue.

There is of course the minor possible problem of chassis distortion - at 100C a 2m tube would be 2.2mm ish longer than a cold tube - I wonder how much this might mess up the geometry.

[Edited on 30/8/10 by coyoteboy]

bi22le - 30/8/10 at 08:56 PM

Ok I think I get it a bit more.

Your engine will be in the back and your rad will be in the front so you want to try and save the weight for getting the water from the back to the front (and return).

I think really its just the case of wanting to risk the whole scalding risk. Also your chassiss welder better be good as you may be chasing water leaks all over the place.

depending on you tube dia inside could you sleeve the inside with a Samco hoose?

Best of luck with it.

bi22le - 30/8/10 at 08:56 PM

Ok I think I get it a bit more.

Your engine will be in the back and your rad will be in the front so you want to try and save the weight for getting the water from the back to the front (and return).

I think really its just the case of wanting to risk the whole scalding risk. Also your chassiss welder better be good as you may be chasing water leaks all over the place.

depending on you tube dia inside could you sleeve the inside with a Samco hoose?

Best of luck with it.

coyoteboy - 30/8/10 at 09:06 PM

I was thinking the main beams would be either bent and single piece or at least pressure tested when complete - nothing would be more soul destroying than to find a leak in that sort of setup! Yes, lining it with some other hose would probably be the safe option but then adding weight so another neg. I need to speak to a vosa friend and see what they consider I guess. Seeing as large diam thin-wall steel is fairly cheap, mega-stiff and not too difficult to weld it's a reasonable option for the build. I'm currently at the stage of having decided on a powerplant and general suspension layout (not the fine details) but trying to hold all the bits with a not too ugly frame. Solidworks is my friend as I have no ability with pencils!

Cheers for your thoughts on the matter, duly noted.

Ninehigh - 30/8/10 at 11:16 PM

Maybe you could pour some sort of heavy duty paint down the inside of the tube, just to give it a lining so it won't rust.

coyoteboy - 31/8/10 at 12:08 AM

Tis an interesting point, though I doubt that I could guarantee a coating. Unless I got maybe a 5ltr container, capped the ends and rolled it around for a while, then emptied it out for drying. Good points.

Ivan - 31/8/10 at 06:36 AM

Lining it should not add too much weight as the hose will weigh pretty much the same as the water it replaces/displaces so my recommendation is to line it.

I think the benefits in accident safety and longevity far exceed the very minor weight penalty (in fact if you select a liner that is less dense than water their might be a weight reduction)

MikeR - 31/8/10 at 07:20 AM

bear in mind, once lined you can't do any welding to that tube - i'd also argue you can't rivet anything to the tube.

Seeing as you've lined it, why not run a long rubber hose? It will weigh similar to the lining and be a lot safer.

(sorry whilst i do like the idea and was rather impressed when I heard about it, for practical repeated road car use i'm not convinced of it).

coyoteboy - 31/8/10 at 08:39 AM

Lining with a hose would makes sense and as Ivan says, if it's replacing some quantity of water (assuming the chassis tube is sized mechanically rather than for the fluid flow) you're lighter anyway if the hose is more dense than water. Fair point there too.

Once lined with a hose you can't modify it, but that's no major problem, if you wanted to modify the tube you'd just pull out the hose, weld, re-insert hose.

I think that may be the way forward, providing I could find a hose that fits fairly closely so I didnt have a hose rattling about in the tubes.

procomp - 31/8/10 at 09:01 AM

Hi

Whats wrong with doing it as per the majority of race cars with this setup. 1 1/4" Id alloy tube either down the out side of the chassis or if you really so desire through the chassis. Any bigger in Id and you will have all sorts of circulation problems.

Cheers Matt

coyoteboy - 31/8/10 at 10:07 AM

Alloy tube in/touching/connected to a steel frame is not a good idea for long lifespan in road conditions, as any peugeot with air conditioning will tell you, the galvanic corrosion problems are a pain. But again I suppose you could coat one fairly well with a lick of paint.

Can you explain to me the reasoning behind the circulation problems with larger pipework, I'm curious.