Lotus Elan

SOME SAGE ADVICE

PostPost by: twincamman » Tue Jan 18, 2011 8:15 pm

its useless to apply the brakes when the car is in the air ---just so you know - :roll: -ed---now would any one care to discuss the superior heat transference of heat by the standard brass /tin rad as opposed to the whim whammy newer aluminium rads???? ed
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PostPost by: garyeanderson » Tue Jan 18, 2011 8:40 pm

Brass is a superior metal for its heat transfer properties, that said, it heavy too. If you really want a brass radiator then I sure you will pay a premium for one. Brass is two to three times the price by weight to Aluminum. And the brass radiator will certainly weigh more. Just call Griffin and get one made.

elan-f14/griffin-scirocco-radiator-install-t15346.html

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PostPost by: alexblack13 » Tue Jan 18, 2011 8:49 pm

Hey Ed, If you are wanting to slow down whilst airborn your going to need flaps mate.. And in my experience the Elan has without doubt the worst elevators I have ever flown with. Just useless!!

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PostPost by: twincamman » Tue Jan 18, 2011 8:59 pm

Hi Gary well Im referring to my super fat rad that came with my car ,it works a treat and I cant see where the weight saved and poorer transfer of BTUs with an aluminium rad would overcome the heat transferred and cooler running of the tin rad --ed
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PostPost by: garyeanderson » Tue Jan 18, 2011 9:11 pm

Brass may be a superior metal for heat transfer but its not going to save you any weight as it ain't that superior to Aluminum at least with the thicknesses that have been used in the past. I have all of my origianal Marsden radiators but they are heavy and are in storage. Use what you like, I do. I don't know anything ya know, I just know how to find crap...

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PostPost by: Famous Frank » Tue Jan 18, 2011 9:26 pm

If you left or installed the brass radiator, wouldn't that lower the height of the nose when airborne? I prefer nose up, it's a lot less stress on the landings.
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PostPost by: elansprint71 » Tue Jan 18, 2011 9:26 pm

Brass is not a better conductor of heat than ally- copper is a better conductor than ally but is heavier.
http://www.engineeringtoolbox.com/thermal-conductivity-d_429.html

Presumably Gary you intended to say copper. Usually only the header and bottom tanks are made from brass, for superior mechanical strength, copper is used for the rest.

I have never seen a radiator with brass conducting surfaces (as far as I can remember, which is not very far). :roll:

There were two thicknesses of Ally radiator for the 26/R- thick and very thick (tech terms). Lots of period photos exist in books and I've read the homolgation papers but can't remember what they say. :twisted:
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PostPost by: garyeanderson » Tue Jan 18, 2011 9:42 pm

Brass is composed of copper and zinc, mostly copper. Both brass and copper both have a better coiffient of termo-condutivity than aluminum but not enough to save any weight over aluminum. I think that today folks are making some very thin copper and brass alloys used in radiators. But I think what we are talking about is a 45-year-old brass and copper unit that Ed has, opposed to the newer aluminum radiators that my link went to. Of cource I am just guessing as I don't know what Ed is up to really.
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PostPost by: twincamman » Tue Jan 18, 2011 11:20 pm

well the old rad is getting a bit thin and springs a leak once in a while but I have a rad shop in town who can duplicate either one -----so for originality[ that I know works ] or new fangled whim whammy ---and better flight characteristics --aye theres the rub -ed
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PostPost by: cabc26b » Tue Jan 18, 2011 11:33 pm

Get the nice whim-wammy radiator, its a life time piece especially if as frank says you land nose up ( and compared to the $200 brake pads quite a deal.)

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PostPost by: elansprint71 » Wed Jan 19, 2011 8:50 am

garyeanderson wrote:............... Both brass and copper both have a better coiffient of termo-condutivity than aluminum but not enough to save any weight over aluminum. .........


Guess you did not believe my previous link; here is a quote from my old metallurgy text-book re thermal conductivity:

Aluminum 247 W/m-K
Aluminum (6061) 171 W/m-K
Aluminum (6063) 193 W/m-K
Aluminum (7075-T6) 130 W/m-K
Brass (70Cu-30Zn) 115 W/m-K
Copper 398 W/m-K

As for the weight issue- can you tell me the last racing car built with a copper (or brass!) radiator? Also, given the relative difficulty of soldering/welding very thin alluminium compared to copper alloys I'm astounded that all those car-designers have made such fundamental errors. :roll:
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PostPost by: garyeanderson » Wed Jan 19, 2011 9:02 am

Thanks Pete

I love being proved wrong as I know someone else had to do some work to look things up. I did a quick search and came up with some sites that had Delta's and theda's and a bunch of engineering terms so I flushed them and just went with my gut. That the luminum ones are lighter...

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PostPost by: rgh0 » Wed Jan 19, 2011 11:27 am

Heat transfer coefficients for the metal used in construction do not determine how well a radiator performs its heat transfer duty. The critical element is air fin surface area primarily and then some more minor details around fins size and length and water side flow tube design and Reynolds numbers and .. and .. and. This is because the transfer of the heat from the metal fins to the cooling air is the overwhelming dominant factor in the heat transfer capability.

Aluminium is preferred in modern race cars and road cars as you can get the required fin surface area in a lighter over all design if you do it right. Most after market radiator designs I see are fairly poor attempts at this and it is not the aluminium that makes them good just more fin area and the fact that they are clean and new compared to the old radiator they are replacing.

The most elegant radiator design for an Elan I have seen is in fact the last small design radiator in the S4's and sprints which is much maligned but is in practice the lightest and most efficient design possible for the orginal Elan. But like most Chapman stuff it needed to be maintained and kept in peak condition to work and not be pushed beyond its limits. Adding lightness saved money and aided performance which were ACBC's aim but it meant the surplus to compensate for age and poor maintenance was removed as it is in many other areas and what made the Elan the classic it is.

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PostPost by: twincamman » Wed Jan 19, 2011 11:40 am

I understand there are two construction methods in aluminum rads--1-- bonded --2--welded ---and that the bonded example does not conduct as well as the welded model -----is this true ??? ed
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PostPost by: rgh0 » Wed Jan 19, 2011 11:56 am

I presume you are talking about how the fins are attached to the tubes. Welded fins will have better long term heat transfer compared to bonded fins. When new the difference will be small but over time corrosion under the bonded fins will reduce the fins efficiency somewhat. However overall this effect will be small compared to fin size and how well you keep them clean unless you have catatrophic corrossion between a bonded fin and the tube it is attached to.

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