eCue said:
I want to mention that the hubsink fin length has me freaked out a bit due to air resistance at speed.
It would be easy to quantify the effect of increased air drag, at least to a first order, by just looking at the no load current draw of your motor at full throttle both with and without the hubsink fins attached. That will give a good idea of the additional losses in watts that you could expect, it's not exactly the same as the extra air drag from forward motion but it should get you in the ballpark.
basically a full time efficiency nut and am curious if the fins need to be so long ? More so if shortening them by say 1/2 would or would not raise the motors internal temperature
When we were doing the initial enclosure development for the Satiator we were playing around with a finned design to to improve the heat conductivity. I wanted them short for aesthetics, like 1cm tall, but it turned out in doing tests that this was barely any better than a flat surface (which is what we went with in the end, see
this post). To get good convective cooling through heatsink fins they needed to be surprisingly long, like over an inch.
In the case of hubsinks, there is forced airflow as a result of forwards vehicle movement and rotation so the situation is not exactly the same. I'd be curious of Sketch wants to chime in on why this initial length was chosen, if it was done from balancing various tradeoffs or just a guess of what felt right?
miunchy said:
Could you please explain why you adding 18 ml of statoraide?
That's easy. In the sequence of doing the tests I first do the incremental addition of Statorade 1 or 2 mL at a time until it's totally saturated to get the curve of conductivity vs. statorade fill levels. Then once I'm ready to move onto the experiments with hubsinks, the hub already has like 16 or 18mL of Statorade in it. So I just roll with that rather than opening up the motor, wiping it dry, resealing the side plates, and then adding a fresh quantity.
When you have QTY's like 5mL you'll get a reduced effect as the wheel spins at higher RPMs (say more than 300 rpm ~ 40 kph). Normally this is fine since most motor heating occurs with low speed high torque travel, but if you did want maximum cooling even at high speeds then you could add a few more mL. For an 8KW peak power hub I don't think you care about additional rolling drag, I'd go with more like 9 or 10mL in this case.