Which controller for Turnigy 80-100?

[drewjet]

Thanks Jeremy. I just feel that depending on which slots you put it in determines the timing. With each slot being 30 degrees apart. but divided by 3 means 10 degrees difference. Too deep for me.

Jay if the shaft is 12mm or larger than I would say yes that should work. Obviously if larger than 12 you would have to remove it and have it machined to 12mm.

 

[Burtie]

Hi Jeremy,

I think drewjet may be reffering to the question raised by Thud on page 1 of this thread:

It may not matter where the halls are placed as long as we maintain 120 deg, But where do you fellers start? between each phase, or centerd on each phase of the DLRK pattern.

This generated a bit of discission on page 2, but no firm conclusions were drawn. Do you have a feeling if it would make any difference where the halls were placed relative to the dlrk winding pattern?

 

[Jeremy Harris]

Hi Jeremy,

I think drewjet may be reffering to the question raised by Thud on page 1 of this thread:

It may not matter where the halls are placed as long as we maintain 120 deg, But where do you fellers start? between each phase, or centerd on each phase of the DLRK pattern.

This generated a bit of discission on page 2, but no firm conclusions were drawn. Do you have a feeling if it would make any difference where the halls were placed relative to the dlrk winding pattern?

I've never bothered to see where in the series connected windings the Halls have gone, I've always just randomly picked three slots and it always seems to work fine. As it's the relative position of the Halls to the magnets that matter I can't see why using any particular set of slots should make a difference. I'd guess that any differences seen might be as a consequence of small positioning errors - it's hard to get the Halls fitted to an accuracy of better than a couple of electrical degrees given the 1:7 ratio between the physical angle around the stator and the electrical angle (1 mechanical degree = 7 electrical degrees for a 12 slot 14 magnet motor).

Jeremy

 

[Jay64]

Ok, the top of the prop shaft is about 10.5 mm but lower down it is about 12.5. I'll have to see how easy it will be to replace or mill down the prop shaft. As far as getting the shaft out, there are two set screws in the end that moves w true shaft and there is a circlip on the other end. Is there anything else holding this thing in? Or is That just magnet strength still holding it.

 

[Jeremy Harris]

Ok, the top of the prop shaft is about 10.5 km but lower down it is about 12.5. I'll have to see how easy it will be to replace or mill down the prop shaft. As far as getting the shaft out, there are two set screws in the end that moves w true shaft and there is a circlip on the other end. Is there anything else holding this thing in? Or is That just magnet strength still holding it.

The shaft will probably be a fairly tight fit in the bearings, plus the magnets can be a bit of a bastard. I've managed to nip my fingers a few times pulling these things apart and putting them together again - one slip and the rotor slides back down hard, usually with a bit of flesh trapped in the gap between it and the base plate................. Once you get the rotor about halfway off the magnet pull gets to be a lot lower.

I keep meaning to make up a puller (really a 'pusher', I suppose), something that would screw into the base mounting holes and have a threaded rod that would just push the shaft out. I may have a go at making one up when the new Collossus bits arrive, as I don't fancy getting my fingers in the way of those magnets.

Jeremy

 

[Jay64]

I just want to make sure I'm not vainly pushing against a shaft that is still bolted in place. :lol:

 

[patrickza]

As far as I know there is no reason not to connect shafts to put motors together. Many have talked about it, but I can't recall actually seeing one in operation.

Here you go:

Jeremy

Maybe another little hijack here, but if you can connect 3, could you connect say 10 for a car conversion? I imagine eventually the shaft becomes the weakness in the system, any idea when that would happen?

Car sized systems are really expensive, especially in AC, not to mention heavy as can be, while 10 of these motors are really cheap and really light! Could it be done? And could more than one motor be controlled with one very large controller?

 

[Jeremy Harris]

Maybe another little hijack here, but if you can connect 3, could you connect say 10 for a car conversion? I imagine eventually the shaft becomes the weakness in the system, any idea when that would happen?

Car sized systems are really expensive, especially in AC, not to mention heavy as can be, while 10 of these motors are really cheap and really light! Could it be done? And could more than one motor be controlled with one very large controller?

It depends how much torque you want to run through the shaft and what material you make the shaft from. Helicopter engines deliver hundreds of shaft horsepower through tiny input shafts that connect to the main rotor gearbox, so such a system is possible, but those shafts typically run at high rpm (maybe 20,000 to 30,000) and relatively low torque. The same approach might work with a linear array of these motors, provided you ran the motors fast enough to keep the torque in the shaft down to acceptable limits. The acceptable limit is going to be fatigue related, so depends to some extent on how long you want the shaft to last before failure and how big the torsional load variations are. If you went for a high tensile strength steel shaft then I think you might be able to run quite a few of these motors in series before you hit serious fatigue problems, but much would depend on a stack of unknowns, plus having the motors carefully aligned.

To give you a feel for the torsional stress it looks like a tool steel shaft 1metre long and 12mm in diameter will deflect about 1 degree for an applied torque of around 1000N-m. I'd guess that you'd need to keep torsional deflection down to well below a tenth of a degree to get any sort of useful life from the shaft, so a working torque of a fair bit less than 100N-m would be the absolute maximum I think. Even then I think you might get a fairly short service life. The real calculations are more complex because the torque is applied at various points along the shaft and it's only at the very end that the full torque is seen. Shaft deflection (which to a certain extent sets the fatigue life) depends on the length of the shaft, so you'd need to plug some real numbers in for expected maximum torque from each motor to get a more meaningful answer.

Jeremy