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GTM Coupe Special
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Author:  derek hambly [ Sun Jul 16, 2017 1:23 pm ]
Post subject:  Re: GTM Coupe Special
Looking good.
For the water pipes aluminium pipe is easier to get and the ends can easily be swaged.
In the past I used 28 mm copper pipe for this as lots of end fittings are available and it can be bent with normal plumbing tools.
Derek Hambly
Author:  Pantera2075 [ Sun Jul 16, 2017 2:53 pm ]
Post subject:  Re: GTM Coupe Special
If you can find a mk1 mr2 in a breakers they have stainless front to rear heater pipes that can be cut down.
Author:  dodo_z [ Sun Jul 16, 2017 6:09 pm ]
Post subject:  Re: GTM Coupe Special
derek hambly wrote:
Looking good.
For the water pipes aluminium pipe is easier to get and the ends can easily be swaged.
In the past I used 28 mm copper pipe for this as lots of end fittings are available and it can be bent with normal plumbing tools.
Derek Hambly


Carbon fibre together with aluminium is problematic in terms of contact corrosion. Copper is really heavy irrespective of the fact, that a diameter of 28mm will be way too tiny for the engine concept.

As far as I remember are the pipes from the MR2 bended several times. I'll have to look if the MG F/TF Pipes will fit, I think they have the desired diameter and are available in stainless steel.
Author:  sanzomat [ Sun Jul 16, 2017 8:51 pm ]
Post subject:  Re: GTM Coupe Special
I'll be removing some stainless coolant pipes soon from the TF I'm currently harvesting bits from. Happy to take some dims for you. Or even let you have them before they get listed on ebay! Might be too long to post easily - you anywhere near Bristol?
Author:  turbocox [ Mon Jul 17, 2017 7:12 am ]
Post subject:  Re: GTM Coupe Special
dodo_z wrote:

Carbon fibre together with aluminium is problematic in terms of contact corrosion.





Can you please explain this statement.

Where did you find this information, and over what time period does it start having problems. :?:
Also what aluminium preparation are you using :?:
Author:  dodo_z [ Mon Jul 17, 2017 1:00 pm ]
Post subject:  Re: GTM Coupe Special
turbocox wrote:
dodo_z wrote:

Carbon fibre together with aluminium is problematic in terms of contact corrosion.





Can you please explain this statement.

Where did you find this information, and over what time period does it start having problems. :?:
Also what aluminium preparation are you using :?:


Of course there are some methods of modifying the surface of aluminium like anodizing which avoid this kind of corrosion, but in the long term the only possibillity is a special ceramic coating which is commonly used for aviation, unsurprisingly it's really expensive ;)

So it's cheaper buying some special stainless steel tubes for sure.


@sanzomat: Bristol is about 1120km from where I live ;)
Author:  sanzomat [ Mon Jul 17, 2017 1:23 pm ]
Post subject:  Re: GTM Coupe Special
dodo_z wrote:
turbocox wrote:
dodo_z wrote:

@sanzomat: Bristol is about 1120km from where I live ;)


I should have checked your avatar box!
Author:  grizzler73 [ Mon Jul 17, 2017 1:41 pm ]
Post subject:  Re: GTM Coupe Special
Quote:
Looking good.
For the water pipes aluminium pipe is easier to get and the ends can easily be swaged.
In the past I used 28 mm copper pipe for this as lots of end fittings are available and it can be bent with normal plumbing tools.
Derek Hambly


I have fitted 25mm o/d tubes on my tub, I am fairly certain a Mk3 Golf rad should fit then. Anything from 22mm to 30mm tube should be fine on a GTM, you don't want to have too much flow, you need resistance as well.
Simon
Author:  dodo_z [ Mon Jul 17, 2017 3:12 pm ]
Post subject:  Re: GTM Coupe Special
grizzler73 wrote:
Quote:
Looking good.
For the water pipes aluminium pipe is easier to get and the ends can easily be swaged.
In the past I used 28 mm copper pipe for this as lots of end fittings are available and it can be bent with normal plumbing tools.
Derek Hambly


I have fitted 25mm o/d tubes on my tub, I am fairly certain a Mk3 Golf rad should fit then. Anything from 22mm to 30mm tube should be fine on a GTM, you don't want to have too much flow, you need resistance as well.
Simon


That depends on the maximum power output the engine has, I think you have a pretty much standard 1275cc engine - I'll go for a 1430cc crossflow engine with approximately something beyond 140DIN PS.
Author:  grizzler73 [ Mon Jul 17, 2017 6:26 pm ]
Post subject:  Re: GTM Coupe Special
Quote:
That depends on the maximum power output the engine has, I think you have a pretty much standard 1275cc engine - I'll go for a 1430cc crossflow engine with approximately something beyond 140DIN PS.

I will have a maximum of 120 bhp if I'm lucky so should be ok, plus i will duct my oil cooler also which should help. The trouble is not so much the pipe size but the combination of the engine is in the back and the size of your radiator, there isn't a lot of room to put a big rad in and then you have to try and get rid of the hot air efficiently. It's a tricky balancing act!
Author:  turbocox [ Mon Jul 17, 2017 9:45 pm ]
Post subject:  Re: GTM Coupe Special
dodo_z wrote:
turbocox wrote:
dodo_z wrote:

Carbon fibre together with aluminium is problematic in terms of contact corrosion.





Can you please explain this statement.

Where did you find this information, and over what time period does it start having problems. :?:
Also what aluminium preparation are you using :?:


Of course there are some methods of modifying the surface of aluminium like anodizing which avoid this kind of corrosion, but in the long term the only possibillity is a special ceramic coating which is commonly used for aviation, unsurprisingly it's really expensive ;)

So it's cheaper buying some special stainless steel tubes for sure




Sorry chap I think I might be misunderstanding something here......

Why does, carbon fibre, cause aluminium pipes, to corrode, due to contact :?:


I have experience of carbon fibre chassis construction, and haven't seen or heard this before. :?:


(this isn't a forum argument i'm just trying to understand)
Author:  sanzomat [ Tue Jul 18, 2017 7:13 am ]
Post subject:  Re: GTM Coupe Special
https://www.corrosionpedia.com/galvanic-corrosion-of-metals-connected-to-carbon-fiber-reinforced-polymers/2/1556

This interested me too so did a quick google - attached link discusses the issues. It seems to be due to galvanic corrosion due to electrolysis. This is common where dissimilar metals are in electrical contact - if you've ever fastened stainless steel with normal steel screws you'll see the stainless will rust really badly (as long as it gets wet from time to time). In that case electrically insulating isolation washers prevent that. Presumably the same would be true for carbon composites and aluminium?

One of the reasons why cars changed from positive to negative earth was that the direction of the DC current caused accelerated corrosion due to electrolysis! The opposite is true where buried steel pipes are protected by cathodic protection/sacrificial anodes.
Author:  turbocox [ Tue Jul 18, 2017 9:54 am ]
Post subject:  Re: GTM Coupe Special
I've gone back and re-read this thread...

So is it your concerned with your water cooling pipes touching your CF chassis and coroding :?:

Can you not mount the pipes so they don't touch the carbon :?:

Can you not use silicone pipes in the areas that may be close to touching the tub :?:


I understand electrolysis between dissimilar metals, but assumed you were talking about aluminium inserts or aluminium honeycomb core,
'inside' of (sealed/no oxygen) the CF laminate.

I work for a blue and silver coloured race team, but we don't use any special coatings on our aluminium inserts for our tubs inside the laminate. But we do alter the surface roughness, as a (key).




Cooling pipe sizes....

My Cox puts out 170bhp (172.4 ps) it uses 25mm cooling pipes and stays cool.

My other Gtm coupe is around 270ish bhp and uses 28mm pipes and hasn't over heated yet. :wink:
Author:  Gottbold [ Mon Oct 30, 2017 9:32 am ]
Post subject:  Re: GTM Coupe Special
crashtestdufmmy wrote:
This interested me too so did a quick google - attached link discusses the issues. It seems to be due to galvanic corrosion due to electrolysis. This is common where dissimilar metals are in electrical contact - if you've ever fastened stainless steel with normal steel screws you'll see the stainless will rust really badly (as long as it gets wet from time to time). In that case electrically insulating isolation washers prevent that. Presumably the same would be true for carbon composites and aluminium?

One of the reasons why cars changed from positive to negative earth was that the direction of the DC current caused accelerated corrosion due to electrolysis! The opposite is true where buried steel pipes are protected by cathodic protection/sacrificial anodes.


That looks pretty good Dodo! Keep up the great work and keep us posted.
Author:  crashtestdummy [ Fri Dec 22, 2017 12:24 pm ]
Post subject:  Re: GTM Coupe Special
Hi. Really like some of your restyling ideas. Love the Elan style nose, in my opinion the original didn't seem quite right. Have had similar ideas for my old coupe, but to make it more 'dinoesque.' As much as I like the original roof line, I do think a rounding of front and rear corners would enhance the shape. I quite fancied curving the rear buttresses\ pillars ( like the Dino), however not sure whether this would effect rear visibility? What do you think? Anyway it's looking great so far, keep up the good work.
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