Power "Sag" when going up a long hill. But not overheating

[rberger]

He's already ordered the Pipe hangers anyway, they have about 357° of compression coverage and draw down without distorting the tube.

I meant to ask you, did you cut the inner lining so it could be put on the boom? (I haven't received them yet but they are on order) i could only get ones with and inner diameter of 1 7/8 and my boom is 1 3/4" I'm hopping I can just cut that inner lining material and have a small gap as well as use that to get them on the boom.

Also been playing with split collars on a PD pad. If the pad is lubed with ethanol just prior to snug & torque the distortion is minimal. No lube and it begins to oval on tightening up.

What's a PD Pad?

Cool Drawing!

Thanks!

 

[Triketech]

HPV uses 60mm tube so I used the 2-3/8 clamps and the fit nice.

PD was meant to be PU for polyurethane. You might take some 1/16 thick PU sheet and cut a 1 x 6 strip to use as a shim.

Teklectic is the other poster one of the most valued contributors to this forum. I believe he wrote the unofficial users guide for the CA3, an exceptional bit of work.

 

[rberger]

Teklectic is the other poster one of the most valued contributors to this forum. I believe he wrote the unofficial users guide for the CA3, an exceptional bit of work.

Yes, I knew, and I've studied that User Guide repeatedly! I REALLY appreciate all the amazing help from you, Teklectic and all the experienced folks on this forum. Both been an inspiration and a guide. Couldn't have done it without all the help!

So I McGyvered the whole thing together with Tie Wraps (my favorite thing right now) enough to test it out tomorrow. Fits pretty nicely. Though it does stick down a bit more than I would like. But it seem to still have plenty of clearance. We'll see tomorrow!

We'll see if this alone is enough to get me up the hill or not. If not, then I'll try the fan. (I don't have the 12V yet)

 

[teklektik]

Thanks for the kind words! (and yep, I did write the Guide as an ES member Back When, although these days I work with JLE as a CA developer...)

TT-
I do acknowledge the considerations in your fabrication work but believe that the projects are fundamentally dissimilar. Your problem is hanging a heavy battery pack (maybe 8-9lbs for a shark pack) from the boom with a moment arm of around 6" or so from battery center of gravity to rotation point on the boom. In the PR case, we are looking at mounting up a lightweight controller heatsink assembly with a very short moment arm. I would guess that the torque differences are in the order of an order of magnitude greater in your case. This is a very different problem.

In the end both of these clamping mechanisms are suboptimal in different ways and so it's a call which advantages or shortfalls to choose. The rigid clamp allows a mount with better heat conductivity while the cushioned clamp allows safe support of greater weight. My suggestion to go with the former was based on the idea that this particular problem centers on removing heat and in the absence of good test data I am a little uncomfortable giving up the direct heat conductive path to the frame.

...the quick summary is that with a heatsink as shown here at 30-40kph ebike speeds, the continuous phase current capability is about 70 amps, while if you just have the bare phaserunner strapped to a tube then it's more like 50 amps.
...
I actually was expecting the bolt on heatsink to make a more substantial difference than this in the time to reach thermal rollback, but results are results!

So looking at the available test results we have for Phaserunner phase amp capacity:

• Free air -- sole plate radiation/forced convection -- (untested - unknown)
• Frame mounted (50A)
• Frame mounted with large heatsink (70A)

Since the PR loses heat in the frame mounted case by radiation and forced convection via the relatively small area of the controller sole plate and by conduction via the smallish frame contact patch with the sole plate, and since the increase in amp capacity by attaching a very sizeable heatsink is a modest 40%, it seems the conductive cooling for the frame mount is likely a fairly large contributor. Although this reasoning may be flawed, it seems that foregoing the conductive heat path with the rubber mount may well have a substantial negative effect on cooling. This made the simple controller flat frame mount, saddle mount, or even a V-block mount look attractive from the limited test data we have in hand. Whether attachment was accomplished by u-bolt, band clamp, or even zip ties was not a primary concern due to low weight and short moment arm (little more than that of the PR mounted w/o heatsink).

Anyhow - valid or not, that was the thinking for the design choice. Shortly the OP will have some subjective results that may help clarify things, so looking on with interest....

 

[rberger]

Will have some results tonite. The current tie wrap configuration doesn't give optimal thermal coupling between the heat sink and the boom. There are two tie wraps in-between the boom and the heat sink. After I completed it I realized there was a way to do it without having that tie wrap in between. But I'll first complete this run as is and then re do it when I add the fan. (Unless it works great as is

When I do make the better direct coupling of the heatsink to the boom, do you think applying a thin coat of thermal compound is worth while? I'm wondering how much the coating on the boom (not sure if its anodized or paint) acts as an insulator.

 

[wturber]

Between their loss of heat due to airflow and radiation and what will surely be a mediocre thermal coupling with the frame (through the paint?) I doubt that having the fin side contacting the frame is likely to matter much at all.

 

[tanstaafl]

Between their loss of heat due to airflow and radiation and what will surely be a mediocre thermal coupling with the frame (through the paint?) I doubt that having the fin side contacting the frame is likely to matter much at all.

I would think that the metal of a frame, even through a thin layer of paint, is a better heat sink than air. You could kill two birds with one stone by mounting the heat sink to the frame with a heat-conductive epoxy. Of course, you probably couldn't remove it then without really messing up the paint.

 

[wturber]

Between their loss of heat due to airflow and radiation and what will surely be a mediocre thermal coupling with the frame (through the paint?) I doubt that having the fin side contacting the frame is likely to matter much at all.

I would think that the metal of a frame, even through a thin layer of paint, is a better heat sink than air. You could kill two birds with one stone by mounting the heat sink to the frame with a heat-conductive epoxy. Of course, you probably couldn't remove it then without really messing up the paint.

Large surface areas (fins) and air movement are used to cool automobile engines, air conditioners, CPUs, etc. Convection cooling is a really good method for cooling. Conduction requires really good surface contact to work well. That's why we have heat sink compound and don't put paint on surfaces when we want good metal to metal heat transfer. The problems with using the frame as a heat sink is the paint and the differences in shapes. You want a large area of really good contact in order to conduct heat away.

 

[rberger]

Well, it looks like having just the Heat Sink seemed to make a big difference as is. I went up the hill and did not suffer from any thermal roll back in the Phaserunner!!!

Unfortunately my body did so I still had to stop a few times because I got out of breath. Even though I'm getting anywhere from 1300 to almost 1800 watts of assist, and I'm putting out between 100 and 180 Human Watts, its still a lot of work for my pretty out of shape body (and its pretty steep at some points on the hill). So I run out of breath about ever 1/3 of a mile on that last mile climb. But before I was stopping because of the thermal roll back. Now I don't see any hint of the Phaserunner getting too hot.

I don't yet know if I could go up the hill without stopping due to thermal roll back. But I suspect I could. When I reached home the Phaserunner was only about 30 degrees Celsius.

I did notice that when I reached the top, the motor was at 107 degrees C and I think the Cycle Analyst might have it start a thermal rollback for the motor at 100 degrees.

Ambient temperature was around 78 to 80 degrees Fahrenheit. Also this time I had already gone about 5 miles on a slight up hill before going up the last mile of the steep climb. So the starting temperature of the whole system is higher than my earlier tests, making this even more positive. The Strava activity that shows the ride is https://www.strava.com/activities/1248510963

So I'm going to declare tentative success.