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Scorpion Motors

Posted: Sun May 31, 2009 1:44 pm
by JimC
Has anyone got experience of these motors?

I am seriously thinking about trying the HK-4025-630KV. 4 of these should give me about 13bhp which would be enough power for a low performance city quad which is the project that I am working on.


Posted: Sun May 31, 2009 2:01 pm
by Jeremy
They look pretty good, Jim, but the high Kv may be problematic when it comes to building a reduction drive.

If you wanted to run these motors at full power, which equates to a motor phase voltage of 45 volts, then they will be spinning at 28,350 rpm. These motors seem to be aimed at the model helicopter market, which normally use small, high rpm motors for compactness.

For this sort of power, you are probably better looking at a bigger diameter/length motor with a much lower value of Kv. I don't think I would recommend the TowerPro 5330-10t motors I have, as both have had bad bearings, but they are about the same power rating as the Scorpion you mention, but with a Kv of 215, plus they are less than half the price of the Scorpion. This reduces the motor rpm at full power to about 9600 rpm, still high, but a lot better than 28,000 odd.

Another motor worth looking at is the HXT range. They are still pretty cheap, so may need to have decent bearings fitted, but are about the same price as the Scorpion HK 4025, yet deliver around 6500 watts with a Kv of just 130.

Here's a link to a supplier with a big range of motors:

Here's the biggest "cheap" motor that I know of: It has a Kv of 130, so at it's maximum voltage of 48V will spin at a much more manageable 6240rpm.


Posted: Sun May 31, 2009 4:20 pm
by JimC
Thanks for that Jeremy, you just saved me a lot of money. The motor I was actually looking at before I got sidetracked looking at pence per watt is the Scorpion S-5525-170Kv. I haven't got an UK price for it but from the manufacturer it is $210. This motor is rated as 2k3W. The reason I am asking if anyone has personal experience is if the blurb is even partly to be believed they are reasonable quality.

Posted: Mon Jun 01, 2009 6:56 am
by Jeremy
The quality issue is a real challenge with these motors, as with a few exceptions, all of them are made in China, a place where quality can be very variable, in my experience. There are only a very small number of quality motor manufacturers that I know of, companies like Plettenburg in Germany, Astro and Neu in the US and one or two in former Eastern Bloc countries.

The Scorpion motors are made in China, but are marketed as being a better quality product. Generally, they seem to have a reasonably good reputation, as far as I can tell, but are probably over-priced for what they are.

The bottom line with these things is that they are very simple, so even a cheap motor with lousy bearings and poor assembly quality can still be good value. Even the very cheap ($49) 2800 watt motors that Bob and I are playing with have perfectly OK machined cases, stators and rotors, it's only the bearings and assembly quality control that seem to be poor. As it only costs a few pounds to replace the bearings, these are still pretty good value when compared to the very much more expensive Scorpion range.

Better still seem to be the big HXT motors. These have been used in quite a few non-RC model applications and seem to perform well. $149 for a motor that will deliver 6500 watts with a Kv of 130, is a real bargain, even if you do need to budget an extra eight to ten pounds for quality bearings and a bit of extra super-glue on the magnets. Certainly I'm going for a pair of the big HXT 80-100-B motors for the project that I'm working up to, as even with the small amount of work needed to bring them up to a top specification, they look to be the best power/quality/cost motor on the market at the moment.