Calculating spring/motor requirement

[blixel]

The minimum torque required will be your design spring load at it initial installed deflection x the radius of the motor shaft gear and the maximum torque required is the spring load at full design deflection times the motor gear radius.

ALERT: WHAT YOU HAVE HAVE SELECTED IS A CRAFTSMAN 11543 HAMMER DRILL. ARE YOU SURE YOU WANT HAT TYPE OF DRIVE? UNLESS YOU ARE VERY FAMILIAR WITH AND HAVE USED THIS TYPE OF DRILL, I WOULD NOT THINK SO; NOR, WOULD I RECOMMEND THAT TYPE OF DRILL FOR YOUR APPLICATION.

Well, when I connect the motor to a DC power supply (like a 6V lead acid battery or DC variable power supply), the motor just spins as I would expect any motor to. It just spins way too fast for my task.

Apart from the function issue of the hammer action of this type of drill, I would expect that its torque far exceeds your requirements i.e. at its rated torque of 420 in. lb., if you put a 1 inch diameter gear or pulley on its shaft, it will be able to pull a maximum of 420 x .5 = 210 lbs of force which I am sure far exceeds the maximum spring load of your device.

At the same time, it does have an adjustable speed and you can get a standard variable speed hand drill with that function; but, I would think that any of those will also far exceed your max load requirement.

Yes, I do think 210 lbs of force is probably more than we need, but if you refer to the video below, I don't think being over powered is an issue. Once the latch goes past the end of the belt, it just releases the spring. But I do need to be able to slow it down. I don't need more than a few dozen RPM at most.

 

[JBA]

An inexpensive standard adjustable speed battery powered hand drill's speed can be adjusted all the way from 1 rpm to it maximum rated speed; and, if you are using the above type of drive then having a excess of torque available is not an issue.

Look for that type of drill and you will find one much less expensive than the one you specified above.

Below is an example of the type of drill I am describing.

http://www.homedepot.com/p/BLACK-DE...PIPHorizontal1_rr-_-205152814-_-202891148-_-N

 

[JBA]

As an adendum on the torque requirement issue, the best place to begin addressing this is to establish the diameter of the sprocket wheel you want to use for you chain drive and multiply that times your maximum spring load and work backwards from that.

 

[blixel]

An inexpensive standard adjustable speed battery powered hand drill's speed can be adjusted all the way from 1 rpm to it maximum rated speed; and, if you are using the above type of drive then having a excess of torque available is not an issue.

Look for that type of drill and you will find one much less expensive than the one you specified above.

Below is an example of the type of drill I am describing.

http://www.homedepot.com/p/BLACK-DE...PIPHorizontal1_rr-_-205152814-_-202891148-_-N

So if I understand this whole thing correctly, the motor I got, plus a https://www.amazon.com/gp/product/B00UMK4NKG/?tag=pfamazon01-20 would allow me to control the speed of the motor?

Though, it does seem like the link you posted is a better value as you get all the parts in one + battery and charger. But am I correct in thinking that the speed controller would accomplish the same thing?

 

[blixel]

As an adendum on the torque requirement issue, the best place to begin addressing this is to establish the diameter of the sprocket wheel you want to use for you chain drive and multiply that times your maximum spring load and work backwards from that.

Yeah, this is also an area of the build that is proving problematic. Once the motor (and speed) are solved, then there is the issue of figuring out where to get a matching gear and belt.

 

[JBA]

So if I understand this whole thing correctly, the motor I got, plus a https://www.amazon.com/gp/product/B00UMK4NKG/?tag=pfamazon01-20 would allow me to control the speed of the motor?

I wasn't under the impression that you already had a motor, I thought you were considering getting the drill you referenced.

 

[blixel]

I wasn't under the impression that you already had a motor, I thought you were considering getting the drill you referenced.

In message 49, I mentioned that I already got the motor. But later in the same post, I did say that I was open to the idea of finding an alternative. For the sake of the project budget, I'm only including the costs for the items that actually go into the finished project. If I end up with extra stuff, I'll return what I can or just use it for some other purpose.

 

[JBA]

I missed the "I got" part of that post statement.
What you keep describing as a motor, because of your application is in reality for the outside world known generally as a "Hammer Drill" and you should use that name for it in your posts so that other do not confuse it with simple electric motors.

In that respect, the controller you are looking at is not suitable to be used with a battery operated hand drill or hammer drill. That controller is meant to be used with standard DC electric "motors".

At the same time , what you are overlooking in the spec sheet for your purchased hammer drill is that it is a variable speed unit all within itself. If you will look at the speed listing on that spec sheet you will see:

Never the less do you really know how a "Hammer Drill" works? They specifically designed for drilling into hard materials using carbide tipped special drills for that sole purpose like concrete so as soon as they come under torque they start a hammering action along with their rotation, like someone hammering the drill into the hard material with a hammer. They do not deliver the smooth rotation that you need for your mechanism.

 

[blixel]

I missed the "I got" part of that post statement.
What you keep describing as a motor, because of your application is in reality for the outside world known generally as a "Hammer Drill" and you should use that name for it in your posts so that other do not confuse it with simple electric motors.

In that respect, the controller you are looking at is not suitable to be used with a battery operated hand drill or hammer drill. That controller is meant to be used with standard DC electric "motors".

At the same time , what you are overlooking in the spec sheet for your purchased hammer drill is that it is a variable speed unit all within itself. If you will look at the speed listing on that spec sheet you will see:

View attachment 115102

Never the less do you really know how a "Hammer Drill" works? They specifically designed for drilling into hard materials using carbide tipped special drills for that sole purpose like concrete so as soon as they come under torque they start a hammering action along with their rotation, like someone hammering the drill into the hard material with a hammer. They do not deliver the smooth rotation that you need for your mechanism.

Ok I was not aware of that. I will definitely have to find a different motor.

 

[blixel]

Well the project is finally over. Yesterday was demonstration day. The design my group chose proved to be too complicated and we weren't able to get a working prototype in time. However, we still demonstrated what we had completed.

At any rate, here are some short (<1 minute) video clips of the teams who did complete a working prototype. Though, only 1 of them was able to hit the 6 to 10 feet target. (I was only able to take video of the other teams. But our demonstration was completely uneventful since we didn't have a finished prototype.)

Team A hit the target twice (per the requirement)


Team C overshot


Team D undershot


The end.