rolling road dyno ventilation question

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Kevin Johnson
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Re: rolling road dyno ventilation question

Post by Kevin Johnson »

Belgian1979 wrote: Mon Jan 04, 2021 5:07 am ... The brake however had a serious problem in the sense that one side of the attachment of the brake to the chassis broke off. All chunks were there and I basically disassembled the coils, welded everything back up and meggered for isolation. All fine now. Now I only need to rebuild the axle with new bearings and so on.
While you (hopefully) still have easy access to the part, it would probably be a good idea to create a diagram/blueprint/drawing on how to replicate it so that if you find that the welded (or opposing side) starts to crack/fail you can have someone fabricate a replacement.

An aside: you will probably become a(n even more) popular guy with your dyno. Make sure your sound suppression system can be adapted for larger/smaller pipes.
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Re: rolling road dyno ventilation question

Post by Belgian1979 »

Well, the classic car scene took a serious hit here, so not so sure about the last one.
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Anielytra
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Re: rolling road dyno ventilation question

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Have you noticed that it gets hotter and hotter every year? Today you can not do without air conditioning. It is especially problematic that they work worse and often fail.
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Re: rolling road dyno ventilation question

Post by donforeman »

I do a chassis dyno service as a part time job here in Oregon. The best fan I have had so far was actually made for fighting fires. They are called PPV fans. The thing just worked and kept the IAT temps in check. Its not like an 8hp, three phase fan, but for the circuits you normally find doing mobile dyno work it did OK. The problem was the fan did not look like anything the magazines show. I had customers insist that I needed to use the big fans they saw in the magazines over and over. It happened so often that one day I just got tired of the the discussion over and over with different "know it all" customers and I ordered the big one they see in the magazines. Now not a word about cooling. It sucks compared to the PPV fan, but the customers stay happy. I need another fan as the big one does so little, so will probably buy a few squirrel cage fans to go with the big one. My thinking is since the small fan and the big one are rated at the same cfm, the smaller fan directed more of it into the engine compartment while the big fan that most chassis dyno places sell has a lot of air going around the car.

This is the small Unifire PPV fan made out of Spokane WA. Its a much better fan for a mobile dyno. Funny story, when I upgraded I did not have the room or the budget to keep both so I sold the smaller fan. I advertised it for what it was, a fire fighting fan. No takers for 6 months even at a very low price. One day I changed the description to say it was a portable green house fan for pot growers and doubled the price. It sold within a day and the guy called me back wanting a lot more fans. Like I said the thing just put out the air for the size.

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Here is the fan I have now. Its made in the USA by Patterson and you can buy the same fan through most chassis dyno suppliers, but I am not impressed. Customer don't give me a hard time any more though about a "tiny" fan.
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Re: rolling road dyno ventilation question

Post by Racer71 »

Would it be possible to make a coil for the retarder and make it water cooled as well? Not familiar with how they are made but seems maybe wrap some tubing around it and a small electric pump and heat exchanger?
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Re: rolling road dyno ventilation question

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Hello. I understand your problem very well. I also had a problem last year. There was a fan malfunction, there was a high noise from work, I wanted to fix it myself, but it only got worse. I looked for help on various forums, but found nothing. Asked "what to do?" from friends and acquaintances, described the situation. A friend recommended these guys to me https://www.airconservicingsingapore.com/chemical-wash/ the guys were very helpful, and they charged me inexpensively. I do not know what I would have done if I had not turned to them, I would probably have spent a lot of money.
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Re: rolling road dyno ventilation question

Post by Belgian1979 »

Racer71 wrote: Fri Jul 09, 2021 6:27 pm Would it be possible to make a coil for the retarder and make it water cooled as well? Not familiar with how they are made but seems maybe wrap some tubing around it and a small electric pump and heat exchanger?
No not possible. The coils are viritually mounted against eachother.
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Re: rolling road dyno ventilation question

Post by BCjohnny »

Racer71 wrote:Would it be possible to make a coil for the retarder and make it water cooled as well?
My first rolling road was made by Danish company H P Anderson (HPA)

The 'coils' were part of the driven rotating assembly that reacted against an annular housing, which was watercooled

Quite a neat set up, discounting the possibly eventual centrifugal effects on the windings
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Re: rolling road dyno ventilation question

Post by Ant180 »

The heat in the retarder has virtually nothing to do with the current dissipated by the coils. It is in the form of magnetically induced eddy currents in the rotor. Effectively the rotor acts just like a giant disk brake would. The same amount of heat as holding the engine against a friction disk brake.
Think about it, if you are making 500hp, that horsepower has to go somewhere. I have had my rotor glow red on my Dyno more than once.
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Re: rolling road dyno ventilation question

Post by BCjohnny »

I don't think anyone's disputing that the large paired vented 'discs' either side of the retarder dissipate the bulk of the energy absorbed, but the coils themselves can suffer significant heat soak, affecting their performance and subsequently retardation irrespective of 'disc' temperature

As the whole of the retarder gets warmer ...... not just the 'discs', and yes I've had 'em glow too ...... efficiency drops

'Telma' coils, or at least all the one's I've had apart, are wound out of Aluminium not Copper high temp insulated conductor, similar to that used in welding sets

Why do you think that is so ?
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Re: rolling road dyno ventilation question

Post by Belgian1979 »

My coils are copper.

The Telma's do loose holding power when heating up. The dyno controls account for that, so if the brake is strong enough it should hold it. However, you definately need cooling.
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Re: rolling road dyno ventilation question

Post by Ant180 »

Sorry, I really thought people were worried about the couple of kw heat from the coils.
Of course, electromagnets taper off when hot, but given plenty of airflow and reasonable duration of runs, it is rarely a problem.
Anybody running that close to maxing out a big retarder on a chassis dyno has got bigger scarier things to worry about, and real heat management to think about from the car.
And if in that case it is still a problem, a second retarder is the best way to do it, rather than mucking around trying to get the last 5% out of a single unit.

I don’t envy anyone who is regularly tuning 1000hp cars on a chassis dyno.
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Re: rolling road dyno ventilation question

Post by BCjohnny »

My coils are copper

While not wanting to argue, I'd say that's unusual ......

A typical Telma coil (one of sixteen) consists of 380 turns of 2mm aluminium wire .......

On another site ...... I believe a member from here

Interesting discussion, and relevant to this

Edit : Don't confuse the flexible copper tails that are spot welded onto the main aluminium windings as the whole core being copper ......
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