3 or 4 rpm motor to lift about fifteen lbs???????

That's a good amount of weight (even for a wiper motor) if you are talking about lifting 15 lbs with no assistance such as a spring or counterweight. If you think a wiper motor will handle it, have you considered just adding a PWM (speed controller) to get the desired RPM? if you get into a decent AC powered gear motor, it's probably going to get a bit expensive.

Diabolik said:

That's a good amount of weight (even for a wiper motor) if you are talking about lifting 15 lbs with no assistance such as a spring or counterweight. If you think a wiper motor will handle it, have you considered just adding a PWM (speed controller) to get the desired RPM? if you get into a decent AC powered gear motor, it's probably going to get a bit expensive.

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I've been sketching some ideas to find the best way to balance the load with different linkages. A counterweight will probably be a must. I thought about the speed controller but but I'm such a cheap A$$. lol!

You might want to consider a linear actuator motor or pneumatics. They will lift the weight but are more money.

Cellar Dweller said:

You might want to consider a linear actuator motor or pneumatics. They will lift the weight but are more money.

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I did look at the electric linear actuators. They're pretty expensive and I'm reluctant due to having no experience with using them or how they work.

Very expensive. just about 4-5 times more but will easily lift the weight. They are extremely simply to work with and operate but have a limited duty cycle. I think the most I have lifted the a wiper motor may have been about 5lbs. Any heavier and the power supply cuts out or you may start bending linkage arms. I have one prop that I'm building now that I beefed up the linkage arm. I'll see what it's able to lift tomorrow before power supply cuts out.

HomeBrew said:

I've been sketching some ideas to find the best way to balance the load with different linkages. A counterweight will probably be a must. I thought about the speed controller but but I'm such a cheap A$$. lol!

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You can get a PWM Controller for $6.29 on ebay from a US seller, that shouldn't break the bank. As Diabolik said, a 15 lb. load is a bit much for a wiper motor especially if if the linear movement is going to be long. Pneumatics would be the best choice if that's an option.

J-Man said:

You can get a PWM Controller for $6.29 on ebay from a US seller, that shouldn't break the bank. As Diabolik said, a 15 lb. load is a bit much for a wiper motor especially if if the linear movement is going to be long. Pneumatics would be the best choice if that's an option.

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Now that is a pretty good deal actually! Lots to think about and thank you all for the input. I appreciate it

What about a treadmill incline motor? I have one and was going to try it last year but never got around to it. I was going to control it with a cycle timer relay

I was going for the lid opening and closing. You need a rotating motor. Maybe an electric linear actuator https://www.servocity.com/assets/images/SD_Linear_Actuator_Side_View.jpg

Thanks, I will Likely use One Of Those Two Options. Still Not Sold On My own Plans I have Drawn Up Here. Still Have Time To Think It Over.

if you go with a PWM controller make sure it is rated for the amperage of the motor you are using, also if you do not what an annoying mun you need one the workd >300 Hrtz

I wish I knew exactly how much the weight was going to be. Would make it easier to make the call

Without any tested plans to go by, you really need to get the mechanism built so you know what the lifting requirements will be. Without that information you're working backwards and guessing at what you'll need. IMO, something like this would be much more effective if it was triggered and not constantly moving up and down, guess it depends what you want. Like I said, pneumatic would be the best option for something like this and it would allow you to easily adjust the action anywhere from a slow upward movement to a quick jump for a great scare. It would also allow you to adjust the retracting speed independently from the extending speed. Just something to consider.

If the prop is going to be so heavy, it might help to add a helper spring to assist in lifting the prop up. Then the motor wouldn't have to work so hard.
Just make sure the spring isn't so strong that it holds the prop up and won't let it go back down.

E-bay usually has cheaper used linear actuators. To use them, you'll basically need two limit switches (e.g., roller arm switches), one at each end of travel for the object being moved (e.g., the coffin lid). These switches need to be wired such that when one end of travel is reached, the limit switch at that end breaks the circuit, stopping the motor. Furthermore, one builds the circuit with a relay controlling the polarity of the DC voltage to the actuator motor. Thus, switching the relay switches the direction the motor runs. After one limit switch is reached and opens the circuit, one then switches the relay (when ready) to start motion in the other direction. Rinse and repeat for the other direction. Shouldn't be too hard for one to work out that circuit. Just be careful to securely and safely wire and mount the limit switches. A failure to stop to actuator would burn it out. This is the setup that I used, anyhow.

I am with J-Man on the thought of going pneumatic. I made a skeleton pop out of a coffin last year by using one 2-way cylinder that opened the lid. I just screwed the skeleton to the lid so that when it opened, he flipped out with it. I wired his arm to the lid so that it looked like he was pushing it.
The voltage that toggled the air solenoid was also routed to a solid-state relay that controlled a light on the interior of the coffin, so that it lit up when the door flipped open. It had one moving part, so this kept it simple = reliable.
-Mike