Hot dip galvanising...
Discussion
quote:I agree entirely. If only chassis and wishbones were HGDed, it would add peanuts to the overall costs (relative to price of car) and save so much hassle (let alone money) on future fettling etc. and would be in keeping with an improvement in build quality of the cars.
I am a great fan of this, would be much better than the powder coating that they use which bubbles if you get chips and the rust travels underneath it.
MC
I don't know how Lotus actually make their chassis so I can't comment on them however with TVR the chassis are welded togeather in a jig while clamped in place, they are then I assume allowed to cool naturally before being released from the jig in order to minimise distortion. When these chassis are then powder coated they go through a low bake oven which raises the metal to a temp just that bit to hot to touch with bare hands but not really that hot they then cool again naturally and hence still minimal distortion or pulling on the welds. With hot dip galv the chassis would have to be effectively dipped in molten metal to be coated and raised considerably higher in temperature than powder coating, because the chassis is no longer in a jig the welds would be heated up again and as they cooled at a different rate to the tubular chassis would then pull and distort in all sorts of different directions giving and end result of a twisted chassis (even more twisted than they are any way 
).
). quote:Has anyone asked TVR to HDG their car's steelworks whilst being built?
pw loves to do things in house by the sounds of things
Powder coating is done at the factory in blackpool.
Galvanizing might be a diffent kettle of fish so perhaps thats why they don't do it.
quote:
With hot dip galv the chassis would have to be effectively dipped in molten metal to be coated and raised considerably higher in temperature than powder coating, because the chassis is no longer in a jig the welds would be heated up again and as they cooled at a different rate to the tubular chassis would then pull and distort in all sorts of different directions giving and end result of a twisted chassis
Construction steel can be HDGed in sections. Welding can be carried out after HDG after surface preparation then the welds painted with zinc paint. Anything has to be better than powder coating (might as well use fairy dust for the good that it does).
There's more than one way to crack a nut!
MC
>> Edited by MajorClanger on Thursday 22 August 11:14
Mel,
I disagree, the TVR chassis is made of bits of straight tube, galvaising wouldn't bend them or make them any longer or shorter. Once it's out of the jig it's not going to bend until it hits the armco
:waiting to be corrected:
Anyway, they galvanise some monocoque cars, shirley they're more susceptible to damage like this ??
I disagree, the TVR chassis is made of bits of straight tube, galvaising wouldn't bend them or make them any longer or shorter. Once it's out of the jig it's not going to bend until it hits the armco
:waiting to be corrected:
Anyway, they galvanise some monocoque cars, shirley they're more susceptible to damage like this ??
quote:
Construction steel can be HDGed in sections. Welding can be carried out after HDG after surface preparation then the welds painted with zinc paint. Anything has to be better than powder coating (might as well use fairy dust for the good that it does).
The problem with welding steel after Galvanising in a enclosed factory type environment as opposed to open air on site, is the noxious fumes issue (cyanide if I remember correctly) very few skilled light fabrication welders will entertain the idea, it also requires air feed hoods and visors, extensive extraction and creates numerous other Health and Safety issue which couldn't be accomodated in the cramped Blackpool environment. Powder coat is applied correctly and of the correct type, with a good etch prime under it should wear considerably better than it does so I do agree there is an issue just not neccesarill that HDG is the solution.
quote:
I disagree, the TVR chassis is made of bits of straight tube, galvaising wouldn't bend them or make them any longer or shorter. Once it's out of the jig it's not going to bend until it hits the armco
The issue is not in altering or distorting individual lengths of tube, but the points of union between tubes where the welds are, a union that is welding either squarely or at a determined angle in a jig will often pull one way or the other after HDG and cause the overall assembly to twist out of square, it is not an exact science, can never be exactly predicted and each time will vary in degree.
quote:Only if using an alkaline bath process. The older 'strip and wire' process is cyanide free. JPCL Document - See Page 9).
The problem with welding steel after Galvanising in a enclosed factory type environment as opposed to open air on site, is the noxious fumes issue (cyanide if I remember correctly)
Now don't get me wrong, I'm not saying that if you weld this you don't get toxic fumes (although generally it is advisable for any welding to be carried out indoors to have an extraction system), but it's just one alternative. Going through the JPCL publication I've linked there's allsorts available. Thermal Sprayed zinc for one.
Anything has to be better than the current system.
Maybe PW does like to keep things in house, maybe it's a cost thing, maybe they're happy with the way sales go... and maybe they just want to have car components that rust quicker than a 1980's Fiat!!!
MC
Cheers Majorclanger, very informative and interesting, my only guess if that sourcing a sub contractor for TVR might pose some problems, i.e with capacity and big enough facilities. Some of the processes listed were news to me and certainly not readily avaliable locally but I will bear them in mind. Even if only because I have a combined sub contract powder coating, electro plating and Galv spend of about £10K a month I need to know what else is avaliable and the pros and cons of each process.
I had the chassis on my M hot zinc sprayed by a company who galvanise lamposts. It cost me under £100 and that included having it shotblasted to clean it up beforehand.
I read somewhere that if they are going to dip it they need to make holes in the chassis to stop it bursting with the heat, but that could be bollocks.
I cannot believe that TVR do not do this, tightwads.
Cheers
D.
I read somewhere that if they are going to dip it they need to make holes in the chassis to stop it bursting with the heat, but that could be bollocks.
I cannot believe that TVR do not do this, tightwads.
Cheers
D.
The issue is not in altering or distorting individual lengths of tube, but the points of union between tubes where the welds are, a union that is welding either squarely or at a determined angle in a jig will often pull one way or the other after HDG and cause the overall assembly to twist out of square, it is not an exact science, can never be exactly predicted and each time will vary in degree.
Yeah, but as (nearly) all of the chassis sections are triangulated should (could) this happen ?? My point was that 3 setions of steel welded in a triangle will stay the same shape even if the joints are stressed slightly differently ?
Interesting thread though, don't usually learn this much at work
Why not try a different alloy? I heard rumours ages ago that the speed 12 would have a Stainless steel chassis. Stainless is more brittle than mild steel but you could compensate with the gauge of the tube and the chassis design. Or how about titanium, since the USSR broke up titanium is less than £10 per kg (lots of ex milatary scrap apparently), which is stronger tougher and lighter than steel and corrosion is prevented by a thin oxide skin. I believe it is a b&gger to weld and I know it is a b&gger to machine but I would be willing pay extra for a lifetime chassis.
Have to say that I'm a little cynical of anyone claiming they will keep a TVR for a lifetime. You'd have to get sick eventually... ;-)
Of course thay may mean the lifetime of the car, in which case take your pick from wet roundabout/ cow shit on bend/ enthusiastic trackday/ lent to a mate/ momentary lack of reason. :-)
As far as galvanising is concerned, I can say yes, it can be a pain to weld. I've done it a few times and usually take a light skim off the area with a grinder and weld outdoors if poss! Then some suitable primer etc.
But I'm not a welder, I'm an electronics engineer...;-)
I recall a magazine article years ago where the reporter visited the Lamborghini factory. The Countach uses a spaceframe made from straight tubes (like a TVR but goes up around the cabin as well, Cerberas do this I think?).
Anyway, they had a pic of two hefty Italians with a 20' scaffold pole passed through the spaceframe; they were jumping up and down on it to correct the twist in the frame once it was removed from the jig. Even simple fabrications twist: I've almost given up trying to be accurate when I fab something 'cos no matter how carefully I align the bits, they still come out skewed! Last time it was two dead simple brackets to hang my airconditioning on the outside of the bungalow: made from 40mm MS angle, they were more warped than Ian Huntley when I took the clamps off....
Ian
Of course thay may mean the lifetime of the car, in which case take your pick from wet roundabout/ cow shit on bend/ enthusiastic trackday/ lent to a mate/ momentary lack of reason. :-)
As far as galvanising is concerned, I can say yes, it can be a pain to weld. I've done it a few times and usually take a light skim off the area with a grinder and weld outdoors if poss! Then some suitable primer etc.
But I'm not a welder, I'm an electronics engineer...;-)
I recall a magazine article years ago where the reporter visited the Lamborghini factory. The Countach uses a spaceframe made from straight tubes (like a TVR but goes up around the cabin as well, Cerberas do this I think?).
Anyway, they had a pic of two hefty Italians with a 20' scaffold pole passed through the spaceframe; they were jumping up and down on it to correct the twist in the frame once it was removed from the jig. Even simple fabrications twist: I've almost given up trying to be accurate when I fab something 'cos no matter how carefully I align the bits, they still come out skewed! Last time it was two dead simple brackets to hang my airconditioning on the outside of the bungalow: made from 40mm MS angle, they were more warped than Ian Huntley when I took the clamps off....
Ian
As with every rule there are exceptions, I know of several TVR owners who have had the same car for over 20 years and a couple even longer than that:-
There is a one owner 2500 in Blackpool, 32 years old, daily driver!!!
Chris Slyfield Tuscan V6, bought from the factory in 1970, still with original owner.
And a customer of mine who has had an 1800S since 1968.
and don't forget Ian-Massey Crosse's Grantura, owned by him since 1975 and that car gets a lot of use.
Generally though some TVR fanatics add to their collection rather than replace so they can own cars for long periods of time.
Going back to the point though, I understood that a spaceframe chassis was prone to twist if hot dip galvanised, I had a M series chassis polyester powder coated in 1993 and when I sold the car earlier this year, 25,000 miles later the chassis was still in brilliant nick. I think that the problem with more modern TVRs lies with the quality (and preparation) of the powder coating done at the factory, after all they are under no obligation to make it last for a lifetime. Also if they made it last a lifetime, some of the long term TVR whingers would have to find something else to moan about, eg my pedal rubbers have worn out after 200,000 miles, etc!!
Also for you youngsters, TVR were the first company in the 70s to offer a 6 year corrosion warranty on chassis's.
TVRs generally are bought for their performance/price ratio and are significantly cheaper than other manufacturers. I know, you will say it still costs £40K, but show me a new Porsche/Ferrari you can buy at that price and match the performance.
davidy
There is a one owner 2500 in Blackpool, 32 years old, daily driver!!!
Chris Slyfield Tuscan V6, bought from the factory in 1970, still with original owner.
And a customer of mine who has had an 1800S since 1968.
and don't forget Ian-Massey Crosse's Grantura, owned by him since 1975 and that car gets a lot of use.
Generally though some TVR fanatics add to their collection rather than replace so they can own cars for long periods of time.
Going back to the point though, I understood that a spaceframe chassis was prone to twist if hot dip galvanised, I had a M series chassis polyester powder coated in 1993 and when I sold the car earlier this year, 25,000 miles later the chassis was still in brilliant nick. I think that the problem with more modern TVRs lies with the quality (and preparation) of the powder coating done at the factory, after all they are under no obligation to make it last for a lifetime. Also if they made it last a lifetime, some of the long term TVR whingers would have to find something else to moan about, eg my pedal rubbers have worn out after 200,000 miles, etc!!
Also for you youngsters, TVR were the first company in the 70s to offer a 6 year corrosion warranty on chassis's.
TVRs generally are bought for their performance/price ratio and are significantly cheaper than other manufacturers. I know, you will say it still costs £40K, but show me a new Porsche/Ferrari you can buy at that price and match the performance.
davidy
quote:
Yeah, but as (nearly) all of the chassis sections are triangulated should (could) this happen ?? My point was that 3 setions of steel welded in a triangle will stay the same shape even if the joints are stressed slightly differently ?
Interesting thread though, don't usually learn this much at work
Weld three bits of steel togeather and yes you may well get a nice triangle, now lay it on its side on a flat slab and watch the wobble where it's twisted. TVR chassis may well be generally triangulated but there not pyramid shaped.
quote:
Or how about titanium, since the USSR broke up titanium is less than £10 per kg (lots of ex milatary scrap apparently), which is stronger tougher and lighter than steel and corrosion is prevented by a thin oxide skin. I believe it is a b&gger to weld and I know it is a b&gger to machine but I would be willing pay extra for a lifetime chassis.
Once your set up it's no worse to weld than St/St the only difference being you need a trailing argon gas shield as a titanium weld needs to protected from oxygen not just during the welding process but also as it cools, hence you use a lot more gas hence more cost, very similar to purging st/st welds. Oh yes also TVR MIG weld most of the chassis which is reletively low skill "mig monkey" work (if you can put tooth paste on your brush you can mig weld) Titanium needs a higher skill TIG weld hence they'd have to pay the welders more
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