Don Slusarczyk (www.donsrc.com) sent me this 59g Don's Wicked Park Pusher outrunner to try out.

It has the same good-quality look about it that the Don's Wicked KA 450H had. It is in pusher configuration with 3mm threaded mount holes at 16mm/19mm. One very minor complaint is that one of the 16mm mounting holes had a motor lead directly beneath it, so that unless very short mount screws were used, one risked a short here. I used the 19mm holes!

I tried some no-load readings and was surprised by the Io - 3.75A @ 10v seems very high. Motocalc indicated a Kv of ~2420Kv (more than the stated 2200Kv), and Rm of ~0.08ohms.

Don had asked me to try 5.5x4.5, 6x4 and 6x5.5, but I started with my favorite Zagi Carbon. It was rapidly impressed upon me that my Power Supply was not going to be up to this motor's demands, so I switched to a bunch of big 2s and 3s packs.

The Zagi drew 23.60A/251W and got me 22.6oz @ 96mph.

The 5.5x4.5 APC E drew 28.40A/297W and got me 21.30oz @ 81mph.

The 6x4 APC E drew 27.80A/294W and got me 29.2oz @ 74mph.

All three props got the motor decidedly warm after relatively brief runs.

I then tried the 6x5.5 APC E and this really sucked amps - the 32.2A/330W using a 3s 6000 Enerland drew the pack down to 10.3v, so I tried a 3s2p 4200 TP ProLite - this maintained 11.2v and I measured 36.5A/401W which got me ~30oz @ 96mph. However, this was clearly more than the motor could handle and at the peak of 400W-in, it was what I can best describe as "misfiring badly". After only a very short run it reached a seriously hot 63C.

I would be hesitant to run this motor, without extremely good cooling, at more than 300W, so I will try a few smaller props and see how it fares.

Cheers, Phil

I have no idea why people are so in love with the 6x5.5 -- it's a dog every time I test it on the ground or in the air.

The numbers with the Zagi or the 6x4 are interesting. Probably be fine in the air.


Dave

Originally Posted by timocharis

I have no idea why people are so in love with the 6x5.5 -- it's a dog every time I test it on the ground or in the air.

The numbers with the Zagi or the 6x4 are interesting. Probably be fine in the air.


Dave

I think "pit bull" might be appropriate - rippping the guts out of the motor!

Dave, do you have any idea why the Io is so high?

***

Originally Posted by Dr Kiwi

Dave, do you have any idea why the Io is so high?

I certainly can't comment competently from an engineering standpoint, but it seems like more than about twice what I would expect.

My best guess though, not being there and all, is a bad bearing or a shaft out of true. Something like that putting excess drag on the motor. This would of course also make it heat up much faster.

My first suspicion is always the bearings. Sometimes they ship them dry, and the Io can be reduced significantly just by oiling. Other times they're just downright crunchy and only replacement helps.


Dave

You are good, Dave!

I pulled the bell off, and it is obvious, from the scoring, that the stator and magnets have been scraping on each other at the rear of the bell (unfortunately I can't show you pictures until my new camera arrives in a few days). Six of the nine stator ends/hammerheads, and eight of the 12 magnets, are affected.

It is hard to tell where the cause lies - there is a noticeable wobble if I spin the bell and shaft up in a drill chuck, though who knows how true the drill itself is.

Hindsight is 100% and I now remember that I did have trouble with prop vibration (very unusual for me since I balance all my props meticulously), and I blamed it solely on the prop!

I just tried the shaft into each of the bearings - there is a LOT of slop somewhere in there - it is hard to tell but I think the shaft diameter is too small for the ID of the bearings??? No, I just tried a 3mm drill bit, and if that is truly 3mm, then the ID of the bearings are too large for the shaft.

Thanks, Dave! I'll hit Don up for another sample.

Cheers, Phil

Woohoo! That sounds like too much slop in the bearings combined with an error in the trueness of the tube. The giveaway here is that only some of the stator teeth are scraped. The weird thing is that only some of the magnets show scoring.

If that's just that the bell has managed to maintain the same alignment all along, then a shaft out of true would be sufficient to cause the problem (usually bowing). On the other hand, if you have both an error in the tube and an error in the shaft (or overlarge eccentric bearings, which could be aggravated or even caused by the original problem) this would be the logical result.

Regardless, it's just a "mechanical." I'm sure Don will be delighted to send along another; these things happen.


Dave

I think the shaft is out of true, it is a very loose fit in the bearings (so the ball races may not even be spinning - it's effectively just a plain bearing!), and the bell may be out of balance... I can get a wicked vibration if I run up the bell and shaft alone in a certain way.

Oh well then. There's always the "all components are out of whack" problem! I'm sure Don's chewing nails about this bit of bad luck. When a motor's that screwed up, it makes me think "shipping damage."

Like, maybe, somebody drove over it with a forklift.


Dave

Let me check the other one I have. Sometimes I have found when I get protoype motors like this, strange things happen to them during assembly.

Don

I wish I could figure a way to check the balance of the bell -it seems a bit out, but I can't fit it in my Prop Balancer to check it. And I have no way to tell if the shaft is not true either. I tried to remove the shaft from the bell, but (even with the set screw removed!) that sucker is in there tight - my 4" mechanic's vise was struggling until I called it quits.

If nothing else you can check the shaft on the edge of your desktop. Just put the bell hanging over the edge and roll it along. If it's grossly eccentric, you'll soon know. If the bell is mounted with a cant, that will show up too.

Most prop balancers can be adapted to work with any shaft by drilling out holes for the rods that connect the two halves. That way you can slide one half (the one you drill out) along the rods to get the correct spacing. Then the bell would "hang" between them.

But you still have the problem of getting an indicator on it.

Me, I'm lazy. I just lend stuff to my buddy Gary who has a precision lathe...


Dave