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Oversizing motor on mechanical press brake


Oct 20, 2023
I'm about to pick up this Chicago 11ton for scrap price.

The plan is to blast and paint it, redo the electrical and make it my own.

It's a 3/4hp motor 1800 rpm. That can bend 14 gauge at 24".

How practical/dangerous would it be to put a 1hp ~3000 rpm motor to maybe get another 30% out of it?

I'd have the motor on a dimmer switch for regular operation.

Ideally I could do 14ga at 4ft.


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Only the motor will not do anything
You need to go to a bigger pressure
The higher rpm gives you more flow No pressure
To get that you have to do something about the hydraulics
Screwing up the by-pass valve perhaps
Keep the 1800rpm at least with that bigger motor

Yea.....That machine looks like scrap for sure...plus you can't spin a pump twice as fast and expect it to perform properly.

Most of all, what's this 'dimmer' BS? You can't run an AC motor on a dimmer, not for long.

Then, keep in mind there are many reasons for a machine's rating...like mechanical strength.

You're in way over your head.
When bending metal, the force required goes up with the square of the increase in thickness. To bend 1/8" requires 4 times the force, rigidity, and power as to ben 1/16".
This is why a 4ft 11 gage manual chicago brake weighs around 2200 lbs and a 16 gage machine weighs 500lbs.
The frame, leaves, and all the other parts of your 11 ton brake would have to be quadrupled in size if you want to double the bending capacity.
Aint no Free Lunch.
Since this is a mechanical press doubling the speed will get you a lot higher flywheel inertia and pressing force.


The other posters tell the truth on increasing force required.

The best way to bend thicker metal on a machine like that is to use a wider die.
I have a die-acro 18-48 and bend 14 ga stainless all the time in a 1 1/2" bottom die, it is only 42" long so that is the widest I can do at this point but it has absolutely no problem with that. It is a hydromechanical, so a hydraulic motor drives a bellcrank to lower the punch down. No rams, no flywheel.
As above bending force decreases with larger die opening.

I would not over speed a cast iron flywheel. If you want to change the motor to a 1 hp 1750 rpm motor to aid in starting effort, great. But increasing speed, don’t do that.
From the pic,it seems to be a heavy steel framed ,fabricated machine,and the makers plate looks fairly modern...........So ,I doubt you will break it if its overloaded ........Ive seen big bending machines actually reverse and run backwards when overloaded ,without apparent damage .