need gear ratio for old PR motors

[artbot]

my win98 pc hard drive crashed along with all my parameters for my crusty old shopbot.

doe anyone have the gear ratios for this motor? any help would be highly appreciated. i have to deliver some parts tomorrow. bad timing.


thank you,
aa

[bill.young]

Hey Alan,

I have the same motors and gearboxes on my old machine in the shop...it was an upgrade from cable drive!

The X and Y unit values are both 1131.768

That tool has the same motor on a ballscrew Z-axis with a unistrut frame. If you have the same Z-axis, the unit values for that are 4000.

Hope this helps,
Bill

[artbot]

thank you so much!!! i procrastinated getting around to the repair, and then realized without a gear ratio, i'll be really going at it blind.

i've had this thing for over 15 years, it never breaks down. (maybe blew two $3 capacitors in that time). but this is my fourth pc.

i'm going to get back there and see if i can wake it up. i am not in any way a "shopbotter". you could learn everything i know about this machine in ten minutes.

[richards]

I should study Shobot's history. I have a drawer full of PK268-02A motors left over from other projects. At one time, I even made a 7.2:1 belt-drive for one of the motors to see if it would be feasible to use on a CNC machine. The motor (driven through a Geckodrive stepper driver) worked great, but I never mounted it on my Shopbot. Maybe I should have pursued that "thought process". A 200 oz*in motor geared 7.2:1 would give 90 lb*in of torque, or, in other words, just a little more than the PRS-Alpha motors produce!

Oh well, those times are behind me. I enjoyed my PRT-Alpha more than anyone will ever know. I was able to try out complicated designs in a matter of minutes, but medications have made it unsafe to work with machinery and age has made it impossible to work with heavy materials, so I camp out at the computer and look for interesting ideas (old or new) that can be improved upon.

(Edited: I just ran the numbers. A "modern" Shopbot controller card, running at 30,000 pulses per second, could jog a 7.2:1 axis with a 1.25" pitch diameter spur gear at a little more than 8" per second. That's all the speed that I would ever need on a production machine.)

(2nd Edit: I re-ran the numbers using a 6:1 belt-drive which would produce 75 lb*in of torque (compared to 80 lb*in on a PRS-Alpha) using a 1.5" pitch diameter spur gear (30-tooth) and saw that a controller producing 30,000 pulses per second could jog an axis at 11.78`" per second. I restricted my PRT-Alpha (with 7.2:1 motors - upgraded) to 12" per second. It looks like the PK296-02A motor with a 6:1 belt-drive might be a contender if properly designed and if a "modern" Shopbot controller were used.)

[artbot]

you are definitely a shopbotter.

i just signed a partnership deal so my next cnc will be an 8' x 14' axyz dual head cnc router. talking about a contrast. i still haven't informed them of my extreme lack of cnc knowledge.