# Noob help needed please



## tot13 (Jul 25, 2007)

I have two questions that I need help with about a rotisserie motor that I'd like to use to move the arm of a Grim Reaper.

First, the motor turns a metal post with a beveled edge. What is the easiest way for me to attach the cam? (With the understanding that I may not be saying this correctly).

Second, how can I know if this motor is capable of handling the weight I intend to put on it? The cam will be attached to about an 18" pvc pipe with a hand that weighs probably 2-3 ounces. The hand will hold a lantern that I'm guessing weighs about 4 ounces. The specs on the motor are: 120 VAC, 60 Hz, 3.5 W, 25mA, and 4.8 rpm's. The motor is made by Timetech. Inc. with a catalog number of S430.1. There is also a stamp of "7830" on the back of the motor. I'm not sure what of this info is helpful so I've just included everything.


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## corey872 (Jan 10, 2010)

#1- is going to be really hard to say without seeing the parts and what methods you have available. Guess you could use anything from welding, bolting, rivets, epoxy or hot glue to attach things.

#2 - so basically you have a shaft 1-1/2 foot long with ~1/2 pound on the end and a 3.5 watt or .0047hp motor to move it.

1.5ft x .5 lbs = .75 ft lbs torque to lift the arm

Torque of the motor = hp x 5252 / rpm,
torque = .0047 x 5252 / 4.8
torque = 5.14 ft lbs.

So the motor should have the torque to lift the arm. That is probably input watts and I'd expect half or more to get gobbled up in friction on a simple motor with high gear reduction, but even that should still leave a bit of surplus.


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## tot13 (Jul 25, 2007)

corey872 said:


> #1- is going to be really hard to say without seeing the parts and what methods you have available. Guess you could use anything from welding, bolting, rivets, epoxy or hot glue to attach things.
> 
> #2 - so basically you have a shaft 1-1/2 foot long with ~1/2 pound on the end and a 3.5 watt or .0047hp motor to move it.
> 
> ...


Corey, thanks for the reply and also for explaining how you calculated the motor's ability to move the weight. I had not even considered epoxy, which is what I think I'll do now, but with this light of a load, I think that will suffice.


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## corey872 (Jan 10, 2010)

No prob. Let us know how it turns out...it works 'on paper' but would be neat to see it in action. One other thought I had - if you have room in the design, you could always add a bit of counterweight to the arm to offset the weight at the 'hand' end. Wouldn't have to be an exact weight, but any little bit would help.


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## tot13 (Jul 25, 2007)

corey872 said:


> No prob. Let us know how it turns out...it works 'on paper' but would be neat to see it in action. One other thought I had - if you have room in the design, you could always add a bit of counterweight to the arm to offset the weight at the 'hand' end. Wouldn't have to be an exact weight, but any little bit would help.


Jeez, do you know how much heartache and aggravation you just saved me? I hadn't even thought of that - and now I realize that a counterweight is a must. I would've been so pissed by the time I realized it myself, and it definitely would've required a re-work. thanks again, and if you think of anything else, by all means, let me know, lol.


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