Cross-sectional Heatsink?

[Juggular]

Are there heatsinks that the fins don't line up with the length of the motor?  

Most heatsinks have fins going the lengthwise. But many motors mount latitudinally. 

I only found a couple of cross-sectional heatsinks, but they are like $20 each including shipping. 

When the Sport Tuned motor costs $15, it makes no sense for me to spend $20 on these.  Has anybody found anything cheaper?  

[RichieRich]

I swear, I always see these in the bargain bins at random hobby shops. That's how I found the one on my Blackfoot Xtreme. That's what you're looking for, right?

[Otis311]

Just semantics but, I would refer to this as a transverse mounted motor. I think the abundance of longitudinal fins mostly comes down to the manufacturing process in which heat sinks are just cut off of lengths of extruded aluminum stock. It would stand to reason that your desire for the fins to align with the direction of flow would produce more efficient heat transfer. With passive heat sinks I like to think the turbulent air, especially at the rear of the car, still moves through the fins. The large fins also emit infrared radiation.

All that said, I have no advice on particular products that meet your needs.

[Juggular]

20 minutes ago, Otis311 said:

Just semantics but, I would refer to this as a transverse mounted motor.

Actually, that makes sense. Transverse is cross-sectional, isn't it?  That's simpler. Ooh, I should've said "cross-sectional."  That's easier to picture in my head.  I'm going to change the title. 

 

[Juggular]

10 minutes ago, RichieRich said:

I swear, I always see these in the bargain bins at random hobby shops. That's how I found the one on my Blackfoot Xtreme. That's what you're looking for, right?

Yes, that!  I did find some cheap ebay deal 7-8 years ago.  But no more. 

I'd say most of the first 150 Tamiya chassis have motors mounted latitudinally. 

The Grasshopper, Lunchbox, Frog, FAV, Hotshot, TA01, M-chassis... even modern chassis like MF01X, XV01, Durga, DT02, DT-3, DT-4 too. 

Is turning 90 degrees while machining so difficult? 

 

[MadAnt]

Yeah it can make a difference passively or having air flow through them in the correct direction. It's just science. Also a little bit of thermal paste under the contact surface might help.

Some brushless motors have fins cut into the case as well.

[OoALEJOoO]

@Juggular There are some relatively low-cost thin heatsinks like the purple one on your picture available at AsiaTees. Also in purple. I hope it's not heatsink designers believe purple cools better .

I guesstimate that the airflow that a chassis gets under its body is perhaps not very significant. My though it is that the air passing on the body skirt creates some sort of turbulence inside the body with just minor general inflow & outflow. Assuming that's the case, fin orientation might not be that important. Much more effect would have the airflow created by an adjacent fan, which at that point the fan direction can be optimized to the fin's orientation.

For open chassis where the heatsink is outside the body, then I think running airflow could have measurable impact on the fin's orientation.

Some time ago I was considering cutting a touring body some holes to allow air getting in. I finally desisted because letting air in might actually create some upthrust by filling the body with air, even if the air is let go at the back. It was just a thought, I never did it.