radiator design

[rjwoods77]

Anyone ever use an air cooled motor?

[jonno]

Rob,
I've seen pictures of what I beleive is an american team at one of the early Formula Student events. They used an air cooled honda v-twin, longitudinally mounted with a shaft output. I've sent you the pic (is there a way to post pictures without them already being on a website?)
I'd be concerned that sufficient airflow was behind the driver to cool the head, especially at the low fsae speeds

[David H.]

Hey Jonathan

I'm starting a FSAE program here at Virginia Commonwealth University (VCU) and i was talking w/ my friend about having our car air cooled. My friend said through his experience with FSAE in Cali their biggest problem was cooling and where to put the radiator so it didn't create much drag. Could you send me a few pics on the air cooled FSAE car you saw. Thanks

~David
formulavcu@gmail.com

[BeaverGuy]

If I was to use an aircooled engine I would probably do it the same way as water cooled engine. I would build ducting to blow air over the engine instead of a radiator. In addition I would probably see how a fan could help the cooling.

[jonno]

David
Hope you got the pic i emailed you of the air cooled car. I'd have concerns about getting sufficient cooling to the cylinder head with it being sat directly behind the driver. you'd more than likely need some impressive ducting to get it working well. If drag is your biggest concern, i'd have thought a water cooled system would minimise this. You don't need sidepods: you can eliminate them reducing frontal area. Brunel have run without sidepods for at least 4 years now

The rad is ground mounted infront of the engine: no sidepods, therefore reduced frontal area & reduced drag. The fan is quite essential however: this sucks air from underneath the car exploiting a nice loophole in the FSAE rules where fans may be used for cooling. Although not to the extent of Gordon Murray's Brabham BT46B, a side effect of this is that you are removing air from underneath the car, creating some downforce.

[alfordda]

Jonathan-

We ran our radiator in the same location for Detroit 04, but we had some cooling issues. Our radiator shroud was pretty poor, it only sucked air through about half of our radiator. Have you guys had any cooling problems?

[jonno]

none whatsoever, hottest the coolant has ever got is 84 degrees C so far: fine for the UK and Detroit. The pic is of BR-4, which is an inferior system to BR-5 - but there are no pictures of BR-5 on the internet yet. BR-5 uses the Davies Craig Booster Pump, not the much heavier - but more powerful - water pump, therefore our flowrates are real slow. However the newer system has minimal coolant side pressure drop, no bends in any of the hoses, cross flow heat exchanger etc. The key is the 200mm x 200mm x 19mm heat exchanger: 98fpd louvered fins (0.076mm gauge material) and similar gauge reformed tubes.
In terms of shrouding, i was particularly anal about getting the shroud airtight (critical) - i can't beleive how many teams "attach" a heat exchanger somewhere in an airstream and expect air to flow straight through it. Our shroud was manufactured from fiberglass. However, I filled the unit along all seams with silicone sealant (including the circle between the fan and the shroud). Also, the fins are extended to the headers: all the air that fan is sucking through has to pass through the fins.
Finally, you want to place your fan as far as you can from the heat exchanger, as there will be a "blind spot" behind the hub of the fan. This is well depicted on this cpu fan site
Hope that's all usefull

[ATOhoosier]

Hey David,
I wish I could help you out but unforunately, funding was pulled for our FSAE team and the equipment purchased or constructed was used for various senior design projects. Sorry i couldn't be of more help the only suggestion I have is try to keep it simple at first. We were going to place it behind the drive and have a fan either pushing or pulling air over the radiator coils. Good luck with the team, I hope you guys have more success than we did.

[David H.]

Wow that sucks that you got ur funding pulled... I'm really hoping that doesn't happen to my team. Thats my biggest fear right now, not finding enough sponsors, and not having VCU back me up. My second fear is aquiring all the technical info needed to build one of these cars. I've been reading the forums for a while and i get lost easily on all the terms u guys use. But thanks for the tips on radiators. I'm thinking of just going for either one or two bike radiators and putting them under the car w/ fans, that seems like the best and simplest idea to me.

[Barnard1425]

As I look at that picture, a few things come to mind. First, with the radiator in that position the exhaust header and muffler are moved to a higher location, thus raising the center of gravity of the car. It also looks like the radiator placement is forcing the team to choose between either a really long car or an unnecessarily upright driver position (again, raising the cg).

Is drag on sidepods really that big of an issue on the tight Detroit courses? Has anybody come across any data regarding drag over sidepods in slower speed racing conditions?