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Unread 01-02-2005, 22:27
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Al Skierkiewicz Al Skierkiewicz is offline
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Re: Burning the FP's

Steve,
I am guessing that the FP motor and tranny is for turning the top arm, is that correct? If so, I am also guessing that you have not accounted for the friction at the turning point. With an 8 lb tetra at the end, the turning friction must be enormous. You may need to put a heavy duty bearing at that point to reduce the friction. I would be careful as you troubleshoot as some teams have reported stressing the FP gearbox to the breaking point. You might also consider some counter weight of some type to balance the load at the top of the arm. Springs or surgical tubing works well in these apps. Pictures would help a great deal.
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Unread 01-02-2005, 22:46
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Re: Burning the FP's

Quote:
Originally Posted by Al Skierkiewicz
Steve,
I am guessing that the FP motor and tranny is for turning the top arm, is that correct? If so, I am also guessing that you have not accounted for the friction at the turning point. With an 8 lb tetra at the end, the turning friction must be enormous. You may need to put a heavy duty bearing at that point to reduce the friction. I would be careful as you troubleshoot as some teams have reported stressing the FP gearbox to the breaking point. You might also consider some counter weight of some type to balance the load at the top of the arm. Springs or surgical tubing works well in these apps. Pictures would help a great deal.
Yeah I will definitely get some pictures tomorrow to post. We have bearings on all those joints; I know the picture I provided is not very helpful. It doesn't seem like its binding anywhere, the system makes for a lot of losses though. The top arm is the one we are attempting to swing, yes. I apologize for the poor grammar and overall laziness


EDIT: Oh I forgot to mention we aren't cantilevering it out there, we have bearings and pillow blocks, I will really try to get some pics up here asap. I also forgot to mention the gears did grind a bit at first because the box was not held tightly enough together (if that makes sense, sorry I'm tired and can't think too clearly right now ) so we used a couple of wood screws to hold it together. We know we probably fried the motor, but were hoping our buds over at 988 or 989 will help us out if we decide to go with the FP's

Last edited by SteveO : 01-02-2005 at 22:54.
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Unread 03-02-2005, 22:29
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Re: Burning the FP's

Our team was thinking using FP motor too, well two FP motor, with 6:1/7:1, maybe even 8:1.

Don't you think 4:1 is a bit fast?

120/4=30rpm.....(i think 0.3-0.2 rps is good..)...or am i too slow?
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Last edited by Projectchon : 03-02-2005 at 22:32.
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Unread 04-02-2005, 10:03
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Re: Burning the FP's

It may or may not be too late in the season to try it, but I think this would be a good application for the Nothing But Dewalts FP transmission. You get a 47:1 reduction in the tranny, which gives you a peak power RPM of around 255. Plus you should get a lot of torque out of it. Most importantly of all, you can leave in the anti-backdrive pins, so your motor doesn't have to melt trying to hold your arm in place.

Team 57 is going with this setup for a telescoping tower for all these reasons, though we're having troubles getting the parts. The clamshells are on backorder, so we've ended up buying a drill to cannabalize the shell from. then when our backordered shell comes in, we'll have a shiny new drill for regionals.
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Unread 04-02-2005, 11:02
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Re: Burning the FP's

I wish I had read that earlier. I am beginning to worry we will burn ours trying to hold the arm up. Maybe I should put some fans on it.... Probly wont help but whatever.
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Unread 04-02-2005, 11:09
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Re: Burning the FP's

FPs we're a big pain is the ASP last year for my team. This year we're using globes alone at a 10:1 reduction (I think - that's NOT my department).
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Unread 04-02-2005, 11:47
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Re: Burning the FP's

gear that devil down... even if it worked with the origional 4:1 reduction, that arm is flying through the air, and when the arm+robot+tetra all runs into a brick wall, thats a lot of intertia waaaaay up in the air... we learned the hard way last year what inertia does to an arm, and what happens when intertia takes over..not a pretty sight.. the tip of our arm, fully extended, will move no faster than 16in/sec..
good luck
j
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Unread 04-02-2005, 11:58
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Re: Burning the FP's

Quote:
Originally Posted by russell
I wish I had read that earlier. I am beginning to worry we will burn ours trying to hold the arm up. Maybe I should put some fans on it.... Probly wont help but whatever.
Figure out how to use a spring/surgical tubing/weight to counter the force of gravity on your arm. The arm should ideally be neutrally balanced so the motor has to pull it down into the starting position. That will be your best shot at not burning up the FP motor.
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Unread 04-02-2005, 12:10
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Re: Burning the FP's

Yep, you gotta gear that F-P motor down quite a bit to make it useful. We are gearing one of ours down by 894:1, which is 7x the reduction of the F-P gearbox alone.

Andy B.
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Unread 04-02-2005, 22:24
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Re: Burning the FP's

Yeah, right now we are gonna use a two stage sprocket set up to gear it down. First will be about 2:1 second will be 4.5 to one. In addition to the FP gearbox. Thats...... somewhere in the vicinity of 1100:1. Then multiply nine times 40 foot pounds (the supposed torque of the FP motor) and our arm should theoretically have about as much torque as some cars.
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Unread 05-02-2005, 09:49
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Re: Burning the FP's

We tried two stock FP Gearboxes with an additional 6:1 reduction (180*6= 1080 total reduction) and it powered our 7 lb, ~4.5 ft arm but drew 30 Amps each when 13 lbs were loaded at the end of the arm. See attached pics #297 & #303.

Not a good scenario for those FP's - design it so they don't have to draw more than 15-20 Amps at full load, otherwise they just might not last. We made a new transmission that has 260:1 reduction (see attached pic #311) and then the additional 6:1 for a total of over 1500:1 reduction. Hopefully this will keep the motors in tip top shape and we still get a couple ft/sec at the end of the arm.
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