- Jun 28, 2011
- Ballarat, AU
Best science based thread in ages.
justin_le said:jk1 said:awesome thread, interesting if you could compare the data with ferro fluid as well.
View attachment 6
Very interesting data coming up next!
icecube57 said:And would it to be better or faster to keep rolling at a lower speed and load or just simply stop to aid in motor cooling.
flathill said:this is pretty much the same with loudspeaker drivers. you only add enough just the fill the gap. adding more will just reduce the efficiency (more drag on voice coil) while providing almost no additional benefit thermally.
also note adding too little will make it more likely to leak
Interesting thought. Wish I had a high speed camera located inside the motor while it was spinning to see just what was going on with the stuff. We thought that the irregularity of the magnets and stator teeth could have resulting in a "pumping" action that would squirt the liquid out sideways, where the centriptal force encouraged it to seep out between the cracks in the side cover plate.this would mean the carrier fluid would leak out the motor while the particles remain in the gap. the ferrofluid likes to travel along crevices. u may want to add grooves to make sure it cant cross the road
icecube57 said:Do yo think a thick stator fluid would have less leakage and running.. assuming at the cost of added drag. Or do you think that if the remaining amount is probably the perfect amount that would remain intact by magnetic forces without it slinging it every where.
Any benefit with a vented setup.
Punx0r said:Excellent work The options you're exploring for sealed motors are particularly interesting because open-sided motors just aren't practical for many and almost certainly unsuitable for a commercial product.
FWIW, I don't think it's at all unreasonable to install the sidecovers with a bead of sealant to prevent leaks. It's a lot to ask the ferrofluid to resist the considerable centrifugal force in a spinning motor, it'd be nice if just refrained from escaping via the bearings or phase wires
flathill said:also note the viscosity lowers as the fluid warms up. there is another "loosening" effect that is not temp related (less particles clumping) after being "worked"
make sure to do the drag test on a "cold" motor as-found after a fresh fill and then repeat the test after the fluid has been worked/warmed
That would be one nice consequence of potting the stator too, we would present a smooth circular OD for the fluid to move around over without all the stator teeth edges and gaps and such. The magnets in this MXUS case are already butted up and make a fairly smooth ID, but in my other motor project I've got a gap between the magnets and would certainly want that filled to be smooth.Also filling the gaps between the magnet and teeth may help with long term fluid stability (less shearing)
and also make sure any glue/paint/whatever is ferrofluid compatible or it can cause fluid separation long term
Hyena said:Those are some whopping big holes in the size covers! They are larger than I'd be comfortable running from a strength/reliability and foreign object entry point of view. I know this was largely to test the best case scenario for the experiment but do you have any thoughts on the biggest holes people should run ? Personally, and without any quantitative science to back it up, I think around 20mm is as large as I'd want to go.
spinningmagnets said:Dave Kaufmann has a Yuba that needs to tackle extra-steep hills, and he kept moving up in "mid mount" motor size to keep from overheating until he got to a de-spoked Cromotor. If we add ventilation holes and a 20-inch rear wheel, I'm sure a 406 would have been more than adequate.
Hats off to Justin and the team for not only doing this, but for publishing it.
icecube57 said:Will the 4T Mxus be updated in the simulator?
John in CR said:Great work Justin!
Regarding the ferrofluid, you mention the drag, but did you see any decrease in Kv?
That's what sparked my interest in ferrofluid added to a hubbie, to increase Kt without increasing copper resistance. If there's that benefit too with the very slight amount that you showed has little effect on drag torque it gets even more attractive.
Cowardlyduck said:Not sure if you missed it, but what did you think about my idea for a clear side cover and UV additive above Justin?
speedmd said:Great work Justin. Now we know the stuff is worth looking at more deeply for certain.
With several different blends/ different volumes of liquid and long test times make this a perfect candidate for a design of experiment (DOE) to get to the pay dirt in much shorter order and have better feel for what is driving the results. You could also add in several cooling fin and venting options into the experiment at the same time. It will blow your mind!