Thread: Corovelo
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Old 12-10-2017, 03:57 PM   #27 (permalink)
The Toecutter
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Rebellion - '16 KMX Framekit Custom electric velomobile
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I came across this a few days ago:

Eternal Cycle Works - Info

I might do a second build inspired by v2.0 after I finish my initial installation. Mine would still be open-wheeled and narrow shelled unlike the designs in the link above, but use a lot of the same build-techniques and styling ques for the shell. Ecky, for your build, you could copy it outright or make your own tweaks to it. I remember reading somewhere that v1 allowed its rider a 19-20 mph average speed(including stops, hills, traffic, ect), fully human powered.

Quote:
Originally Posted by Ecky View Post
How do you feel about adding a few tablespoons of oil to the motor housing, to help with transferring heat from the stator? It seems preferable to me to cutting vents, given that I'll be riding in salt and grit.
You could try it. I haven't powered this motor yet myself and I would first investigate where it was generating the heat. What kind of oil, how many kJ can that volume of the oil handle before it changes state, and how many J worth of cooling will it have per unit of time at given speeds?

If I were going to go through all of that trouble to concern myself with heat tolerance instead of just using it stock, I would install ferrofluid for purposes of heat transfer and absorption capability at the cost of a very tiny efficiency loss(if it's even noticeable). Then I would later drill holes and vents and install fans in all the necessary places(shown in that ES topic pertaining to this motor) so I could load more power into it without damaging or destroying it. This motor has been pushed to 10 kW for seconds at a time by third parties on that site, and that potential for peak power output is probably the biggest advantage to modifying this motor. It makes a lot less heat than a MAC if what I've read is correct. I will eventually know first hand what kind of heat it makes under load when I get my pack installed(it won't be for at least a few more months as the body is still in progress).

Otherwise, I'd leave it alone. From the experiences of others, it appears to be reliable for 1-1.5 kW for the duration of the pack discharge depending on ambient temperature, and 4 kW for a few seconds at a time. Will that little bit of oil on the case make a difference in that? With a high enough phase current limit set by whatever controller you have, 4 kW could possibly move you like a sport bike from 0-10 mph, haul ass like a decent performing car from 10-20, and still perform like a slow, out-of-tune car from 20 to top speed. If you need any more performance than that, you might as well go all out and rebuild the motor for it if you're going to be worrying about excess heat at all.

10 kW is perfect for a few seconds at a time when/if you get your motor capable of tolerating it. Before it's ready to overheat after taking off from a stop, you're at the max vehicle speed limited by gearing, voltage, and/or rpm. Then you're load is whatever is necessary to retain cruise at that speed which may be at or under the motor's continuous power rating if you get the aerodynamics right(unless you're going uphill, in which case you have to pay more attention to heat).

Quote:
Originally Posted by jjackstone View Post
For clarification, does this mean you believe that power to the drive wheel is about .75 x 630w = 472 w? Just wondering because for a normal unfaired upright or even an unfaired tadpole it can take 650-700 watts to hit 30 mph.
JJ
The power to drive the rear wheel is whatever it is. Ecky gave us preliminary power versus speed figures. 75% electrical to mechanical power conversion is probably a close guess to its actual real-world operating point at Ecky's quoted speeds. Coast-down tests can be used to get Crr and CdA numbers, and the computer used can provide more data pertaining to motor/battery energy consumption(as long as it is properly calibrated).

472w is a good guess for rear wheel power requirements based on his numbers. In contrast, the leafbike motor plus controller/battery should be around 85% efficient combined for the same operating point, meaning 550w or so would be the new estimate for power consumption. The estimate is crude and doesn't account for increased inertia losses or different bearings or the fact that the MAC can be mechanically decoupled whereas this Leafbike motor cannot. Nor does it account for any accessory loads that could also be draining rhe traction pack.

However, with a sufficiently aerodynamic faring, much greater efficiency is possible than what Ecky is quoting. There exist electric velomobiles that can cruise at 30 mph on flat ground for under 10 wh/mi.

Last edited by The Toecutter; 12-10-2017 at 04:21 PM..
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