Cooling system help

[KevinRCCA]

I was wondering if you guys could point me in the right direction here. I am the Sr. Editor for Radio Control Car Action Magazine and I am building a radio controlled 1/5-scale trophy truck from scratch. It will be powered by a water cooled Zenoah engine (I would love to have a scale V8 but can’t afford it) and I am going to machine my own head for it so that it will have large fins and a larger area for water to circulate around. My questions are about cooling systems. Do you guys have any tips on cooling systems? I’m trying to figure out how the ones that are used for miniature engines work. I know I need a radiator and a way to circulate the water and fans to cool the radiator. But is there more that I’m thinking about? Are there companies out there who sell custom or premade radiators? I have a design for one and plan on making it out of aluminum but if I can find a more scale unit, that would be much better for my project. You can see the beginning of my trophy truck build on my blog. The link is below. Thanks for your help ahead of time.

Kevin Hetmanski

http://blogs-rccaraction.com/profile_blogs/Kevin_Hetmanski/&action=view&id=1577

 

[mu38&Bg#]

Take a look at liquid cooled computer gear.

http://cgi.ebay.com/Koolance-HX-CU1...High-Flow-/160465633579?pt=LH_DefaultDomain_0

 

[KevinRCCA]

I've looked into those but they won't work for this truck because they are all the wrong size. Thanks for the response!

 

[gbritnell]

Hi Kevin,
The first thing that you'll find is you can't use a scale radiator. It won't provide enough cooling. The second thing is that the radiator will need to be shrouded to provide enough air flow through it to pull the heat off. As far as making it out aluminum the problem arises when you have to make water tight joints. Unless you are a welding wizard with a TIG system there is no practical way to make it out of aluminum. A copper or brass based radiator will work as well and can be soldered together. If you are going to make it water cooled why would you go to the trouble of putting fins on it?
gbritnell

 

[stevehuckss396]

The idea of fins is good. Why not get some extra cooling.

Like G said, scale rads are not going to get the job done. I am currently working on a 1/5 (little bigger) V8 and the radiator will be made from brass. It will look like a mid 70's chevy style side tank. It works because these engines wont see the running time that an Rc truck will see. This thing could be shrouded and computer fans installed in the shroud. Dont know how well it would work but it "looks" to be scale. If you decide to build your own, you could do something like this.

http://www.homemodelenginemachinist.com/index.php?topic=9609.0

 

[KevinRCCA]

Thanks for the information guys. I totally didn’t think about making a shroud and I do plan on using computer fans on it. I’m not a wizard when it comes to welding aluminum but am getting pretty good at brazing aluminum. I’ll either do that or use some sort of epoxy to hold the pieces together on my aluminum radiator if I can’t find one.

Steven I’ve been following the progress on your engine and I am very impressed. I’d like to feature the engine in the magazine when you’re finished. Email me at [email protected] when you’re done!

 

[mu38&Bg#]

Are you putting radiator(s) behind the cab or in the front clip? I thought most had the in the back, but I'm not sure. What size is it going to be?

 

[KevinRCCA]

I'll have it in the front clip and I might have another in the rear.

 

[TroyO]

Hmmm, if you were planning to run a fan then presumably you have some decent amount of battery power available on it.

Maybe enough to "cheat" the cooling system using a peilter device? If you haven't run in to them, they are electronic devices that get hot on one side, cold on the other when you apply current.

That effect can be used to increase effeciency in a cooling system, effectively "pumping" the heat from one place to another.

You still need to get rid of the heat somewhere, but maybe you can sink to the frame and let the whole chasis be part of a "stealth" cooling system, and keep the radiator more scale-ish?

Edit: Forgot to add a link to some.
http://customthermoelectric.com/tecs_imax.html?gclid=CKreg5i8q6MCFUsJ2god9WtA3g
BTW, love the magazine!

 

[KevinRCCA]

That's very interesting. I'll have to look into that. Glad you like the mag!

 

[Longboy]

..........This is a tough one for you. A stationary engine has more latitude in liquid cooling where the restrictions for your model truck revolve around packaging within the body of the vehicle and the added weight of the cooling system and fluid may make your truck noncompetitive. Unlikely all this stuff is going under the hood. I see these trucks are like 25 inches long and if its a custom built chassis, you can custom build a body with wheelbase to accomodate the hardware. 1) I would make a stake bed body, hang two automotive transmission oil coolers from each side with twin 'putor fans drawing through each one and you might not need a reserve coolant tank or 2) if a pick-up bed, hang one cooler on the rollbar with the reserve tank (disguised like a pick-up truck tool box) in the bed too. ;D

 

[T70MkIII]

Given you are putting a radiator at the front, can I suggest using aluminium tubes to take water to and from the engine? It will heatsink a lot better than rubber or silicone hoses, and may compensate to some extent for the smaller size of radiator.

 

[Kermit]

Car heater cores. They are about the right size to be a 1/5 scale radiator.

http://www.google.com/products/cata...og_result&ct=result&resnum=3&ved=0CE4Q8wIwAg#


Just a thought,
Kermit

 

[steamer]

Hi Kevin,

How much power is the Zenoah putting out continuously? In Horsepower would be fine, but any unit of power you can get your hands on would help. Perhaps their website has and engine rating? From there you can do a rough size for the heatload..assuming some engine efficiency and from there assume a coolant flow rate. From there you will need to determine how much performance from a miniature water cooled head and radiator you can get, per unit cooling area, so you can size the radiator.....and hopefully it's not bigger than the back of the truck, in between the roll cages, where I see them on SC trucks.

Now, if you ask me, there is going to be too many assumptions here. Your going to need to measure something. If you have a water cooled head design in mind, you could build it, set the engine on a test stand, and measure the flow and temperature of the coolant into and out of the head such that the engine, under race conditions, stays cool. At least you will know. My guess is that is a big number on a high power density model truck engine.

A picture or a drawing would be useful too... ...and why water cool if the head is air-cooled already....just to be to scale? Does the water cooled system have to do all the cooling, you could it be just enough to puff a little steam/glycol out the overflow so it looks and smells like the real thing......you could do that with the exhaust heat at the tuned pipe. It would defintely be much lighter too...never a bad thing on a race truck.

Anyway....We still would like to see pictures!.... ;D

Best of luck to you, and if we can help I think we would be glad to!

Dave

 

[KevinRCCA]

The website for Zenoah doesn't list a horsepower for their engines and I see horsepower numbers all over the place for this type of engine. Let's go with 2.5 for argument sake. The truck is being built mainly for the cool factor. Performance is the last thing on the list. If it moves, I'll be happy. The reason why I am going with a air/water cooled head is for the "cool" factor. Basically, why not do it. I don't expect much air to reach the engine because it will be located behind the cab so the extra cooling that the water can provide will help.

 

[mu38&Bg#]

Water cooled RC boat engines have surprising small requirements for flow. But, they have an endless supply of cool water. When you make a closed loop system all of the cooling occurs in the radiator. The Zenoah G23 car engine is rated 2.15kW at 14kRPM in the manual. This means your radiator should be capable of dissipating 2-4kW of heat or more in the highest ambient temperature you expect to run in. Of course the hotter you run the coolant the more heat you can dissipate. http://www.thermatroneng.com/products/720/dc_series720.html The 2-4kW is a guess based on typical heat loss for engines. Efficiency for a small two stroke could be lower than estimated and heat losses greater than this.

The liquid PC guys started with heater cores. The thing is unless you're familiar with, or can look at a lot of heater cores, you have no idea what size they are.

 

[KevinRCCA]

Car heater cores. They are about the right size to be a 1/5 scale radiator.

http://www.google.com/products/cata...og_result&ct=result&resnum=3&ved=0CE4Q8wIwAg#


Just a thought,
Kermit

Sorry I didn't reply to this before. Didn't see it for some reason. Those heater cores look the part. Does anyone know the dimensions of these things?

 

[Longboy]

Looking on Ebay there are several thousand heater core listings. Some with dimensions.

 

[TroyO]

Transmission coolers might be another option.

http://www.jcwhitney.com/fin-and-pl.../p2000858.jcwx?filterid=j1#prodDetailTabPanel

And yet another might be an Air Conditioner condenser.

In short... LOL, I'd go shop at a junk yard,

 

[SAM in LA]

You might try your local auto parts shop. I have been allowed to go through there stock rack with my tape measure to find what I needed. Also, the manufactures may have an on-line catalogue with dimensions of there heat exchangers.

SAM