Motorizing Manual Pipe Benders

Can you estimate the length of the crank lever and the amount of time it takes to turn it one revolution? Combining the first with the estimated 50-100 lbf gives the torque required; further combining with time will translate into horsepower. Then you can select a gearmotor that matches or exceeds these rpm, torque, and horsepower calculations.

The length of the handle from center to center is 18.5 in. But wouldn't the length of time to turn 1 revolution depend on how fast you turn it?

"But wouldn't the length of time to turn 1 revolution depend on how fast you turn it?"

ummm...

I think if we knew, in your experience, about how fast you do turn it, and how many times you turn it, then we can zero in a little bit. As an example: you rotate the handle 18 complete revolutions, and it takes about 30 seconds to bend, and another 20 seconds (cranking the opposite direction 18 rev's) to return to the starting point. This gives me 90⁰ bend.

Can you give us something like that with real numbers?

I have a bit more information for you now. He is bending 7' aluminum extrusions, the outside is square, he takes a few breaks each time he runs the extrusion through, it takes 17 turns and 3.5 minutes (turning) per linier foot.

Is this all the info you wanted?

Thanks

Sounds like a 3hp 1750 rpm 480VAC 3ph motor coupled to a 25:1 reduction gearbox driven by a VFD would offer you a very wide range of flexibitly and tweakability. 3hp may be a bit more than needed but the price difference between a 1hp and 3 hp is minimal. Power consumption is more but not by any great amount.

Well...

If the material is square on the outside, it is probably square on the inside as well. If this is so, it is tube, not pipe. From your description, it sounds like a roller, not a bender. I know this seems trite, but it is a different machine.

Richard L (in #7) has it spinning pretty fast, I think.

• By hand, 17 Revs / 3½ min ≈ 5 RPM, with a torque responsive drive (if you hit a stiff spot, you crank the handle a little slower, or you stop). Production is (7ft pc @ 1ft/3½min) ≈ 25 min/7ft stick.

• By motor, 1750RPM ↓ 25:1 = 70RPM. Throughput will be (17 Rev/1ft)70Rev/min ≈ 4ft/min. Production will be (7ft pc @ 4ft/min)≈ 2 min/7ft stick.

Now, it seems a great thing to speed production up this much... but is the existing equipment up to this? Hand operated machines are seldom as robust as powered machines. This is, in the end, your decision.

You are correct about the speed if you run the suggested VFD up at 120Hz but if one was to run the VFD at lets say around 30Hz the final speed is considerably slower. The OP leaves out a lot of detail and what data is given is questionable such as the time required to complete a bend. This info is based on hand cranking the bender and may very well include a couple of rest breaks. Minimum time to complete a bend was never given. No mention was given to concerns of heat generated during rapid bending or anything else.

My design idea allows the OP to complete a bend in about 5 seconds/ft to about 30+ seconds/ft depending on his desire of the moment. A 1750rpm motor running at 60Hz connected to a 25:1 reduction gear gives 70rpms. The same motor ran at 30Hz yeilds 35rpms. If this does turn out to be too fast it is a simple matter to use a 30:1 all the way out to a 100:1+ reduction gearbox. Then he could look at reducing the motor down to a common and very cheap 1/2hp motor and take all the time in the world to bend his material.

Again these are just ideas being floated but personally and from an equipment manufacture viewpoint, if I'm going to motorize a manual labor proccess I would also want to remove as much time as possible. Of there is the standard so long as it is safe and does not damage the product or machine clause.

If you have access to 480VAC 3phase power then the modification is fairly simple and cost effective.

Before contacting your local supplier for a motor and gearbox have the following basic information handy.

First one you have> How much torque at full load with be needed to turn the drive gear.

How many revelutions will the drive gear need to make for a full bend.

How fast do you want to complete a full bend. 30 seconds? 5 Seconds? faster will mean more horsepower.

What is the available power for the motor.

Shaft size to go from the gearbox to the drive gear.

With this basic information a local supplier should be able to size the proper gearbox to the properly sized motor and motor RPM. For variable speed control you may also want to give consideration to a VFD drive option, there are several low cost models on the market.

I did exactly what you are asking about some years ago with an older version of this. You just have to make a die adapter for the bender shaft and make a jig for the bender bench to steady and secure the drive. The support is very important as the torque of these machines can be dangerous! Also, there is a lot of trial and error involved when you are making the bends in that a near exact number of turns is required for replicating bends of desired degrees with the different sizes and materials. This motor will give you more than you may want in a bend if you don't stop soon enough.

I would presume that you have some experience bending and if you don't, prepare yourself for a pretty good learning curve and lots of tube or pipe to practice with.