rolling road dyno ventilation question

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Belgian1979
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rolling road dyno ventilation question

Post by Belgian1979 »

A while back I talked about a rolling road project based on a Telma retarder that I had been working on.
I'm wondering how much air flow is needed to get rid of the engine/exhaust heat, how much airflow in front of the car to keep it from overheating and how much airflow is need to cool the retarder.
Maybe someone has a rough idea
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Re: rolling road dyno ventilation question

Post by Caprimaniac »

A large fan...
How to turn GURU in an instant.....
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Re: rolling road dyno ventilation question

Post by Rick! »

https://superflow.com/wp-content/themes ... ev3-20.pdf

Make up air is going to take considerable effort if extended running is the goal.
Blowing air on the retarder is going to take serious air.

If just making power runs is the goal, the effort is lessened considerably.
I ran chassis dynos in the basement floor of an office building and in multi-bay shops.
Using an large exhaust fan to pull on the floor exhaust system worked real well.
Turbo engines are a challenge as they heat up oil real quick and even fans in front of the radiator don't buy much running time.
It goes without saying, running an oil cooled Porsche is a real challenge. I've done a lower end Ruf once and one needs to keep clear of the flames out the exhaust on decel... :)

Claytons used a water brake so dyno heat was kept in check.
I've watched stupid people burn up Eddy current axle dynos running them too hard too long.
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Re: rolling road dyno ventilation question

Post by Belgian1979 »

Yes, the goal is to tune the ignition, so I expect it to do some steady state running.
I understand the difficulty in keeping things cool, which is why I'm asking.

I was thinking about a 4500 m³ fan in front of the car (possibly 2). One of ca. similar size on the brake and then a similar one to generally draw the air out of the garage. Door of the garage will stay open all the time.
I will route the exhaust outside via pipes.

I had the car on a rolling road dyno in the area (not to tune, but for a couple of runs. The guy complained that it got really hot in there quick. Knowing a C3 Corvette, I can only imagine that :(
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Re: rolling road dyno ventilation question

Post by barnym17 »

Since a telma is just a series of electro magnets cooling it shouldn't be to tough they live in a pretty low airflow environment on my busses.
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Re: rolling road dyno ventilation question

Post by Belgian1979 »

The magnets needs some cooling and part of it comes from the vanes on the rotors. However if the coils heat up too much they tend to lose some magnetic field, which reduces the holding power, which is not really wanted.
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Re: rolling road dyno ventilation question

Post by barnym17 »

A blower off an old furnace may provide enough airflow to cool the telma.
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Re: rolling road dyno ventilation question

Post by barnym17 »

What would really be neat is to control each magnet separately instead of just the normal 4 stages that would a lot of flexibility to your project. Then If we can find a math genius to figure out how to calculate the shaft horsepower.
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Re: rolling road dyno ventilation question

Post by Truckedup »

I get my bikes done at the shop doing only bikes and snowmobiles ...the dyno room is about 20 ×20 with one 10 x 10 overhead door. Some of the stuff tested is air cooled.... a 12 inch duct from a roof top blower is used for engine coolng and fresh air...It's a huge volume of high speed air.There is an additional 30 inch portable fan at waist level blowing toward the door For air exhaust the overhead door is opened....Cars have more exhaust flow.....
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Re: rolling road dyno ventilation question

Post by Belgian1979 »

barnym17 wrote: Thu Dec 31, 2020 4:53 am What would really be neat is to control each magnet separately instead of just the normal 4 stages that would a lot of flexibility to your project. Then If we can find a math genius to figure out how to calculate the shaft horsepower.
I have that one figured out. 16 coils with 0.6 ohms resistance at 12 v. When you put them in series they can be regulated as one single unit. Voltage then is 192VDC. The current is around 20A at full power.
I'm in the process of acquiring my acquisition system and power regulator through here:
https://yourdyno.com/the-yourdyno-instrumentation-kit/

All control of the brake is done with PID control (rpm setpoint) and through laptop. The neat thing is that it can output 0-5V based on the torque measured by the brake. I can input this into my megasquirt EFI from where I can irl analyse the data and adjust timing in a sweep per cell.

The only problem is that tuning is limited to a maximum of about 10 minutes in a row. The brakes according to the Norwegian's get quite hot and the braking power trails off to about 50% after 20 minutes.

So yes I need huge amounts of cooling to be able to do longer tests. That is not counting the air needed to coil the SBC and get rid of the exhaust heat (which is also tremendous)
Just need to figure out how to get the brake test bench with rollers, the telma (heavy piece) and all of the fans into my back shed and still be able to fit the car onto it :lol:
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Re: rolling road dyno ventilation question

Post by barnym17 »

what do you already have?
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Re: rolling road dyno ventilation question

Post by Belgian1979 »

The bench with rollers, the telma and a couple of air extractors. Going to buy the daq and power supply soon.
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Re: rolling road dyno ventilation question

Post by Kevin Johnson »

Don't forget to get some advice about suppressing the sound so you do not get complaints.

I know some people direct the sound straight up into the air but depending on the weather conditions, sound waves can reflect downwards and be heard some miles/kilometres away. That happened ~40 years ago when my classmates took a very powerful stereo system into the woods in Michigan and got complaints from miles away.
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Re: rolling road dyno ventilation question

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Re: rolling road dyno ventilation question

Post by Belgian1979 »

Yes, sound reduction is also a concern. I still have to tackle that, but I think of using a big drum in which the exhaust ends with some intermediate baffles towards the outlet.
Testing will be limited to 10-15 minutes before cool down, so it's not like I can constantly run it anyway.

As the guy in the thread says the amount of friction created by the rollers is key. I have an old brake bench to work with. Everything there. It has the advantage that the rollers are coated with some very good friction material and it has 2 rollers coupled with a chain per tire. About 8" in diameter. The disadvantage though is that the rollers are quite small in diameter. As I will not be able to test for a very long time I don't think this will pose much risk on tire explosions.
I'm also not trying to test very high rpm/high power situations. The main goal is that I want to set the ignition timing in the low to midrange rpm mostly and maybe a short power run to measure total amount of torque/power.

The advantage is that I have the biggest brake that Telma had, the CC300 (3000 Nm braking torque), which is basically needed as the torque holding trails off with increased temperature and I need some reserve. 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.
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