First ride with the thermometer inside.
Very interesting! Outside temps were 65-70 F and the ride, the usual 15 miles home, about 1000 ft of uphill and 300 ft downhill vertical along the way, no wind.
Cover temperatures and temperatures measured on the hub body, where the magnets are maxed out at 90 F. But inside on the windings where the thermocouple is, went up to 155! That seemed to be the max for todays weather. Because it was cool, I tried climbing the big hill, 500 feet in a mile, no pedaling at all. Temps at the bottom were around 117, and a few minuites later, at the top, 148. After the hill, comes 5 miles of mostly uphill, with very light grade, almost flat. Eventually the temp climbed to 155, but at a rate of about a degree per mile.
At the very start of the ride, with the hub at about 60 F, temperatures climbed quickly to about 100, in about 4 miles. 130 by about 6 miles, and then it sorta stalled there, reaching 134 by 9 miles and the start of the hill. I took a shopping break in Kmart, and resumed the ride with a temp of 117.
After arriving home, the hub cooled to 130 pretty quick, in about 15 minuites. When I rode another 3 miles, on nearly flat ground, the temp gradually returned to 145 by the time I rode three more miles.
A few conclusions become evident from a single test like this.
1 Cover temperature is much less than the interior temperatures, at least in moderate weather. 65 degrees hotter inside than outside in this test! So if you are feeling for a warm hub, if it feels hot, it is very hot inside. Interesting, since my brushed hub often runs with a cover temp of 140, Is it really 200 F inside? !!! No wonder I melt a brushed hub in this climate! If hub cover temps are getting up to 120 or more, the inside may be getting too hot to continue without risking damage, assuming it's 170F or so inside.
2 At some point, the hub seems to reach an equilibrium, where cooling is getting close to keeping up with heat from inside. I suspect this is very affected by weather, with the point where the hub starts to slow it's temperature rise going up with hotter weather and lower humidity.
3 Continued riding at full throttle may cause a nearly infinite rise in temperature. Even if the climb is slow, the hub seems to keep getting hotter for the entire ride, at least for a ride of 15 miles. There may be, for each hub, a definite maximum full throttle ride length, which varies with the weather.
4 Stops at stop lights show a definite cooling effect. A long enough stop light can cool the hub 5 degrees. So intermittent use of full throttle should help keep the motor cool. On the section where the ride home goes up and down short rolling hills, the hub temp climbed very little, but where the grade was shallow but steady uphill, the temperature would climb steadily. So pausing to peadle some, or coasting down a hill, can help cool the hub. On really long rides, a few 15 minuite breaks should help.
It will be very interesting to see just how hot this hub gets when I ride this June. But all last summer, in the hottest weather, I had no problems with my second brushed hub as long as I kept the ride under 10 miles. The first brushed hub, that I rode 15 miles at a time, melted in 400 miles. So anybody worrying that lives in the desert, can stop fretting about it if thier ride is less than 10 miles. I think what happens is the epoxy on magnets gets gooey and continuing to ride past that point is where the magnets start moving around the motor, so damage is dependent on how much time is spent at hot temperatures. As soon as you stop, the hub cools, and epoxy gets hard again. Hopefully by summer I will have definite safe ranges for different ambient temperatures so we can ride along knowing if it's 95, we can ride this far, and just how much less if it is 100, and so on. I know from others experiences that as long as the hub is not too hot to the touch you can keep riding. But some ballpark ideas of what is a safe ride and what may not be in the summer will help, so we don't have to worry till a certain point in the ride, and then we can check the temp and decide to continue or rest a bit.
