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Motorized Bottle Jack Press

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Hi guys!

I've started building a motorized bottle jack press inspired by this one http://www.forgemagic.com/bsgview.php?phot...mp;by=ptpiddler

I bought some 1000mm x 25mm W1 in roundbar and it was much harder to forge down than i thought. :blink:

I'm trying to find out if a motor I've got would be able to drive the press and how best to do it. I've got a 20ton bottle jack and the motor is 1600w 2840rpm.

Can you guys tell me if I'm screwing up the calculations?


First the bottle jack, I need to find out how much force I need on the lever to get 20tonns out of the jack.

Here's what I think:

The pistons range of motion is 24mm for each cycle of the piston the jack cylinder moves 0.9mm up (I measured this by pumping the piston 50 times and measured the amount the cylinder moved and divided it by 50).

Then I find the difference with: 0.9/24 = 0.0375.

I find the load needed on the piston to generate 20tonns of pressure at the cylinder by: 20000kg x 0.0375 = 750kg.

Now I find the force I need on the handle that drives the piston by taking the lever lenght = 240mm (end of lever to the hinge), and the lenght from the piston to the hinge = 30mm: (30 / 240) x 750 = 93.8kg.


Now the motor:

The motor is 1600w = 2.146hp.

1hp = (33000lb x 1foot) / 1min = (76.047kg x 1m)/1sec.

One down stroke of the lever measured at the end = 190mm

The RPM of the motor after gearing it down with a 15mm radius wheel on the motor and a 150mm radius wheel driving the jack lever. (15 / 150) x 2840 = 284rpm.

Time of one down stroke: 60sec / 284rpm = 0.211sec / 2 = 0.105sec.

1hp = (76.047kg x 1m) / 1sec = (400.25 x 0.190) / 1sec = (42.02 x 0.190) / 0.105.

1600w = 2.146hp = (90.18kg x 0.190m) / 0.105sec.


So the engine will be able to generate 19.229tonns with a jack cylinder speed of 4.25mm per sec, this seems really fast to me, what do you think?

I will have a speed controller on the motor but I don't know how that will effect the engine power, is it 1/2 speed -> 1/2 power?


Does this look right to you, or am I way off here? There's a long time since I did anything like this in school so I had to dig it out in the back of my head and with a lot of help from the internet. ;)



Here's an illustration I've made of how I see the press setup:


Front view (from operator):



Back view:



Blue: "bottle jack".

Red: lever for opening/shutting valve on the jack.

Yellow: springs to pull the jack open when valve is opened.

Light blue: axle mount with ball bearing.


Do you think the push rod from the wheel to the jack lever will hold up or should I have a wheel closer to the lever?


Thanks! :D

Marius A. Bacher


"To learn and not think over what you have learned is perfectly useless. To think without having learned is dangerous." - Gore Vidal

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I'm very interested in this set-up, I hope it works out...so I can build one too :) I too need a cheap but more importantly, quiet solution to drawing out big stock.


Rather than a fixed gearing/speed, why not rig it up with a "clutch" So you can have some sort of control over how fast the jack is being pumped?

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Marius, nice idea there. I have often wondered how to apply a bottle jack press to forging. I hope that it works out. Please keep us posted.


One thing that you said about having a difficult time forging out 25mm W1. I just forged out some W1 that was twice that diameter the other day and didn't have any problem moving it with a 1.5Kg hammer. Are you letting the steel get hot enough? You need to get W1 a little hotter than some of the lower carbon steels. I usually start forging up in the yellow range and then correct for any grain growth with multiple normalizations.


Doug Lester

HELP...I'm a twenty year old trapped in the body of an old man!!!

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That's pretty darn cool. Thanks for sharing.

My life is like shaving with a razor sharp machete. It's a bit awkward and I feel a sting every now and then, but in the end I'm happy with the results.

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Hi Marius,

Your calculated speed of 4.25mm per second may not be as quick as you're hoping. I think on hydraulic presses, 1" (25.4mm?) per second may be considered on the slow side of the speed range. Maybe you could be quick with your release valve or rig up stops so that the press doesn't open all the way. If it opens just enough to move the work over, it might save a little time/heat.


Good luck with the project, Craig

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Thanks for the encouragement guys! :D


Leif, I bought the W1 (105w1) from the company in Netherlands called TELMA Knife Steels that you pointed me to, their W1 is listed as 40mm x 500mm round on the site, but when I asked, it turned out that they had 1000mm x 25mm too, so I ordered 4 peaces. I paid about 1500kr ($290) including shipping tolls and tax.



P.Abrera, I have been thinking of using a "clutch" mechanism that work sort of like the "tire hammers", but I don't really have any good ideas on how to incorporate something like that into this design. If you have any ideas please share them with us :)


Doug, I might have been a little on the cool side, but it was what I call yellow and it took some time to get to heat.

You might also be stronger and more conditioned than I am, I haven't really forged that much yet. I can't wait to get some knifes and swords out of my new steel. :D


Craig, yeah, maybe I can solve that by making some sort of adjustable stops, holes in the frame where I can insert some bolts so that the jaw doesn't open all the way between heats/strokes, what do you think?



Again thank you guys very much for your comments, and keep 'em coming! ;).

I would really appreciate if anybody could confirm my calculations, I'm at the point now where it would be bad to go further and realize that my math was off and have to scrap a lot of work. :blink:

Marius A. Bacher


"To learn and not think over what you have learned is perfectly useless. To think without having learned is dangerous." - Gore Vidal

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4.5 mm/sec is way too slow. You want to have an inch/sec or better, otherwise you'll die of old age cycling the cylinder.

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Marius, something that you may want to consider, since you are in Europe, is a flypress. They're pretty rare over here in the states, but they're manual presses that are very usefull for forging, and can be had for quite reasonably inexpensive prices in Europe. A forging flypress uses a 4 lead screw and a large mass at the top to impart a huge amount of force for very little effort, and can be used for a variety of forging operations including forge welding and drawing out.


If you dont want to spring for a hydrolic forging press, a fly press is a great (if relativly obscure) alternative


I have a small flypress (sorta between #2 and #3 size, about about 300lbs) though I dont have a picture of it setup in my shop, just the one I took the day I purchased it.




Justin "Tharkis" Mercier


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I think an air operated jack would work better,My hydraulic press moves at 2.5 inches or about 150mm per second.Power output is relative to the size of the dies,small dies need less pressure than large ones,its all about psi.Although the more power(within reason) the better.Air jacks are cheap here,as are used air compressors.

Edited by McAhron

N'T McAhron Sqwaukin Vulture Verrinder

"to create is to make art"

TREMBLING EARTH KNIFE WORKS (website coming soon)

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