Fans inside vented hub motor - anyone tried it?
- Thread starter neptronix
- Start date
icecube57
10 MW
Search for Arlo and fan.
John in CR
100 TW
Arlo has a number of them in his X5 to both stimulate intake flow by blowing from the intake side of the stator to the exhaust side, and he has some blowing at the stator iron from the center. He gets good flow through the motor even when stopped.
If this is for your Pie, you won't need fans though unless it's for lots of low speed stop and go. Your small tire for more rpm, and large diameter motor make for much greater centrifugal flow if done well, not the so common big round holes in a pizza pan approach.
If this is for your Pie, you won't need fans though unless it's for lots of low speed stop and go. Your small tire for more rpm, and large diameter motor make for much greater centrifugal flow if done well, not the so common big round holes in a pizza pan approach.
I can't find anything about arlo's results, even using google.
John; can you define what doing it right is?
I was thinking about big slots.. not the 'drilled rotor' approach.
If ya got a thread link, awesome..
John; can you define what doing it right is?
I was thinking about big slots.. not the 'drilled rotor' approach.
If ya got a thread link, awesome..
sn0wchyld
100 kW
ive done it, with good success in a ht35. I used 3 laptop blower fans running on 5v, and it makes a notable difference, both to running temps and cooling times. just recently I went for a couple of rides where I rode my bike like a motorbike, ie no pedaling, racing around locally and generally having fun. lots of stop start/wot etc. after about 45min or so I finally hit my alarm at 90deg, which has never happened with me riding it like a bike, even up 20% grades. without the fan it gets there notably quicker (i forgot to switch on the fans a couple of times), though ive yet to do the real numbers. best part is the side covers/magnets stay very cool, I haven't measured other than my hand but they only ever feel warm, maybe 35 tops.
cooling averages about 1 deg every 10 seconds, worst case scenario. that's averaged over a drop from ~85 to 45 after a fairly long 10-20% climb, at about 25deg ambient. the drop from 85 to around 65 was much faster than the drop from 65-45.
this is running 100v 40a in a 17"mx rim, equivalent to a 23" bike rim. rider + bike about 140kg.
all in all well worth it... i dont really think about motor heat much any more, the alarm is conservative that nothing should die, and I've never hit it in normal riding, and it takes ages riding like a motorbike. check the buildlink in my sig, ill post an update about it this weekend since I should have some more spare time then...
cooling averages about 1 deg every 10 seconds, worst case scenario. that's averaged over a drop from ~85 to 45 after a fairly long 10-20% climb, at about 25deg ambient. the drop from 85 to around 65 was much faster than the drop from 65-45.
this is running 100v 40a in a 17"mx rim, equivalent to a 23" bike rim. rider + bike about 140kg.
all in all well worth it... i dont really think about motor heat much any more, the alarm is conservative that nothing should die, and I've never hit it in normal riding, and it takes ages riding like a motorbike. check the buildlink in my sig, ill post an update about it this weekend since I should have some more spare time then...
John in CR
100 TW
neptronix said:
I did slots on my first one...too much friggin work with the dremel. At the end I worry about some of the exhaust flow escaping too early before passing over the end windings.
I'm about to ventilate my Hubmonster motor, which is roughly the same diameter as your pie. I've come up with a new idea intended to stimulate flow through the air gap too, which I'll explain fully with pics in a new thread after I do it this week. In the meantime think of your motor as a centrifugal fan. The spinning side covers make the air spin and centrifugal force pushes the air to the perimeter creating high pressure there and low pressure in the space between the windings iron and the axle. If you allow air to escape at the perimeter and intake toward the center you will have a flow of fresh air through the motor.
Optimizing is a matter of maximizing flow with centrifugal fan like placement of holes (extreme perimeter for outflow like a squirrel cage fan), interior blades to deflect flow away from the covers toward the windings creating more turbulence over the windings before exiting, and shaping the holes so the outside influences of the spinning wheel on a moving bike don't counteract the natural centrifugal flow and during the most influential part of the rotation (where a hole is furthest from the road and moving the fastest relative to the outside environment), it actually stimulates more flow by creating a low pressure region at the exit behind the trailing edge of the blade. This last part means holes or blade-like slots that are angled for a rearward exit when they are furthest from the ground, which creates a left and right side cover. DoctorBass got the angle backward on one motor and it had heat problems, because the outside influence essentially fought against the centrifugal flow. Slots to create more of a fan blade shape would be the ideal, but the magnets are where we need to put them, which is obviously impossible. Optimization in our case means right against the lip that locks into the magnet retaining ring, because that's as close to the perimeter as we can get, and air flowing out their must flow past the windings on the way out.
An 11" diameter centrifugal fan spinning hundreds of rpms can move many hundreds of cubic feet of air per minute. We can only get a decent fraction, because out covers also support the weight of the bike so we're limited on cross sectional area we can open in the best location.
Hopefully that was a coherent and understandable stream of consciousness.
Sorry, but I'm tired, but I did a good bit of research on the subject, and my ventilated motor in use proved the concept correct. A smoke test I did showed the motor drew air into the intake below 10mph or 168rpm with a 20" wheel, and flow increases drastically with speed.John
I haven't tried it, but in the pikes peak/ magic pie thread I think I described the possibility of installing them in there. I can't remember the details though--not sure if it was my own idea post or me just working out what someone else proposed.
