My PK296-02AA motors are too low on power output, what can I do?

[knownuttn]

I have PK296-02AA motors on my CNC currently... When I got them I thougt to my self, "Oh Yeah" these will kick butt.. However much to my suprise, I can not get very high RPM out of them. SO Question is, should I invest in gearing these up by using Timing belts and pullies OR should I simply replace them?

Thanks in advanced

[domino11]

See what JR did for a belt drive reduction!

http://www.mechmate.com/forums/showthread.php?p=11184&postcount=299

[Richards]

How do you have the motors wired? Series or half-coil? If they're wired half-coil with a 70VDC power supply you should have no trouble at all in running them at 250 RPM, which would give you at least 13-inches per second with a 1"-pitch diameter spur gear (20-tooth). I've run that motor at over 1,500 RPM on my test bench with a moderate friction load. In fact, it's my second favorite motor. I like the Oriental Motor PK299-F4.5 motor slightly better, but I wouldn't feel handicapped if all I could find was the PK299-02AA motors.

If you gear the motor via a belt-drive for a 3.6:1 gear ratio with a 30-tooth spur gear, you should be able to run at 400 to 500 RPM, which would be in the 8-ips to 10-ips range. I do most of my cabinet part cutting on my Shopbot PRT-Alpha at 6-ips (going faster gives a cut that requires too much sanding).

[Gerald D]

The PK296-02AA are short (single stack rotor) motors which are unsuitable for our size routers if the pinion gear is directly on the motor shaft. However, if geared/belted down with at least a 3:1 ratio, they work very well.

Your motors are only about 66mm [2.6"] long. If you want to do direct drive, you need a motor about 96mm [3.8"] long. (the longer motor has a second set of magnets on the rotor, doubling the torque output)

[Richards]

I've got egg on my face. When I read the post I thought I saw PK299-02AA instead of PK296-02AA. Gerald is right. That motor is the same physical size motor that Oriental Motor uses in the SGxx geared motors. (Oriental Motor probably uses a six-lead version of the PK296-F4.5 motor to make the PK296-SGxx geared motors. When you closely compare the data sheet for the PK296-F4.5 motor and the PK296A2A-SGxx motor, you notice that both motors have the same inductance, the same voltage and the same resistance. They rate the SG motor at 3A instead of the F4.5's 4A, probably because of the gearbox, but in all other respects they are identical.)

The PK296-02AA motor would have about 70 lb*in of holding torque with a 3.6:1 belt-drive attached. At 500 RPM it would still have about 33 lb*in of torque with a 3.6:1 belt-drive gearbox. Compare that to the 22 lb*in of torque permitted with the SG3.6 gearbox and you'll see that a belt-drive attached to that motor would be a significant improvement.

Again, sorry for being careless in reading. I actually read the post twice and both times got it wrong.

[Gerald D]

Mike, I read it 3 times and still wondered why Knownuttn thought it was underpowered . . . . . . eventually realised it was the short motor as a direct drive. Those model numbers rattle me every time I see them!

[knownuttn]

Thanks for the information... I will try the belt drive method..

Again, Thanks

[Marc Shlaes]

Ask JR for the DXFs. The belt drives work great.