One-Way as Motor Bearings?

[etard]

I am trying to come up with a freewheeling system that does not add too much width and am playing with options. one option I was thinking could be one-way bearing inserted inside the motor ( 2 or 3) in such a fashion that the whole motor shaft would spin freely while coasting and then engage the stator when powered up. It would require a large motor shaft to use the one-way bearings, but why not make it hollow? My bike uses a 20 mm hollow front axle that is super light and I'm sure very strong to take the abuse of DH riding. I'm sure a hollow shaft would have a few advantages anyways, can't think of any off hand though.

Just wonder if any motor designers have considered this option?

 

[damonjackson_spl]

Nice idea.. I wonder if you could swap the bearings internally over to one way bearings?? Would that work??

 

[gwhy!]

I can say for sure if it will work for everyone but I have played around with 10 and 12 mm id one-way needle bearings on the jackshaft and this have been fine upto around 2kw and can prob take a lot more ( But there is a lot of variables with different setups ) so I don't see why you couldn't put one on the motor shaft instead, I think the 10mm id bearings are 10mm wide. I cant quite see using one-way bearings would work as motor bearings thou.

 

[etard]

That's interesting on the jackshaft, huh? That means the power has been multiplied a few times over. How many are you using and what brand?

I wonder what happens when the one-ways finally give in to the power, do they slip like a clutch until the torque catches up with speed? Or do they just slip out and you have to let off the throttle and try it again slower and easier? I guess I'm gonna just have to order some and see.

 

[gwhy!]

That's interesting on the jackshaft, huh? That means the power has been multiplied a few times over. How many are you using and what brand?

I wonder what happens when the one-ways finally give in to the power, do they slip like a clutch until the torque catches up with speed? Or do they just slip out and you have to let off the throttle and try it again slower and easier? I guess I'm gonna just have to order some and see.

The bearings that I have been playing around with are only cheap ones something like this http://cgi.ebay.co.uk/HF1216-NEEDLE...ntrolled_JN&hash=item5193020ec5#ht_1437wt_906 I was only using 1 bearing. I must add I havent used them for any length of time so whether they will be ok for continued use I have no Idea yet. The bench testing I have done with these bearings I have not had one slip at all.

 

[Hillhater]

That's interesting on the jackshaft, huh? That means the power has been multiplied a few times over.

Well, i guess you mean the torque is higher on the jackshaft, because the "power" will be the same, ..you cannot increase power with gearing, only torque.

I wonder what happens when the one-ways finally give in to the power, do they slip like a clutch until the torque catches up with speed? ....

If you "over-power" them..usually they chew up the shaft they are running on or slip and generate so much friction heat that it destroys the complete bearing. They are not designed to slip like a friction clutch, just to act as a one-way lock up device.

 

[nieles]

I am trying to come up with a freewheeling system that does not add too much width and am playing with options. one option I was thinking could be one-way bearing inserted inside the motor ( 2 or 3) in such a fashion that the whole motor shaft would spin freely while coasting and then engage the stator when powered up. It would require a large motor shaft to use the one-way bearings, but why not make it hollow? My bike uses a 20 mm hollow front axle that is super light and I'm sure very strong to take the abuse of DH riding. I'm sure a hollow shaft would have a few advantages anyways, can't think of any off hand though.

Just wonder if any motor designers have considered this option?

for an outrunner motor; what if you put an oneway ball bearing between the motor shaft an the motor can. at the end of the motor.
using this bearing http://cgi.ebay.com/CSK12PP-One-way-Bearing-Sprag-Clutch-Freewheel-Backstop-/400120288492?pt=LH_DefaultDomain_0&hash=item5d290714ec

it is a bit hard for me to explain my idea but i hope you get the idea

 

[etard]

Yes Nieles, I think it might work well in an outrunner on the bearing between the shaft and the can. Although, it might be difficult bonding or pressing the one way bearing in so that it does not spin in it's housing. I really want to try this now!

 

[nieles]

the outside of the bearing can be locked in with a setscrew in the keyway.

the inside can be done the same way. bore a hole in the shaft, put a pin in the hole
and slide the bearing on its place.

Niels

 

[Kaz]

I'm planning a rc-motor + Golden Eagle drive ring setup and for adding freewheeling, the one-way motor bearing idea seems at least worth a try.

For the motor I've been eyeing the TGY AerodriveXp SK Series 63-74 170Kv http://hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=7870. Does anyone know what size bearing I should start looking for it? I'm also open for other motor suggestions with about the same specs.

Or is it really even worth the time and money to add freewheeling in this kind of setup. Can you really feel the motor dragging if you drive with just muscle power?

(First post. Yay.)

 

[etard]

Welcome Kaz,
Maybe go find a motor rebuilding thread on rcgroups.com, those guys are always rebuilding these motors with better bearings. I will do a search myself as I am interested as well. You don't have to use a freewheel setup if you use the 6 FET sensorless controller, but if you use an RC controller the backpedalling will blow the controller by way of BEMF. Basicly throwing current in the opposite direction that is supposed to ( I think).

Edit:
Found it for you according to a guy on Hobbyking website forum (complaining): 19mm OD x 10mm ID

 

[Kaz]

Thanks for pointing out the BEMF problem. I hadn't even thought about it, but now that you brought it up it sound pretty obvious.

The bearing mod is starting to look like it might be a bit too risky for a first project so I think I'll skip it this time. Hopefully someone else has the time/skills/money to explore further, because as an idea it sound really tempting.