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Benders and Bending Which bender is best? How do you use a bender? How do you calculate bends? Everything Bender related...


Benders and Bending Which bender is best? How do you use a bender? How do you calculate bends? Everything Bender related...

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  #21  
Old 06-22-2016, 05:48 PM
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Quote:
Originally Posted by TheBandit View Post

There are 3.79 liters per gallon, so if you want to convert lpm to gpm, you can divide by 3.79. 2.24lpm / 3.79=0.59 gpm
Per AMERICAN gallon. A standard gallon is 20% bigger.
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  #22  
Old 06-22-2016, 05:53 PM
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So 1.6cc pump motor 2800rpm
= 1.6x2800/1000 = 4.48LPM ?
Am I on the right track?
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  #23  
Old 06-22-2016, 06:01 PM
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Quote:
Originally Posted by alwaysFlOoReD View Post
Per standard 'MURICAN gallon. An imperialist gallon is 20% bigger.
Corrections above in bold.

FYI my calcs above are based on 'murican US gallons so if you're buying parts made of aluminium and you look under a bonnet to change your oil, you may need multiply by 1.2.
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Last edited by TheBandit; 06-22-2016 at 06:06 PM.
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  #24  
Old 06-22-2016, 06:02 PM
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Quote:
Originally Posted by ducas99 View Post
So 1.6cc pump motor 2800rpm
= 1.6x2800/1000 = 4.48LPM ?
Am I on the right track?
Yes! Assuming you directly couple the pump to the motor. If you throw pulleys and belts or chains or gears into the equation, then you need to factor those in.
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  #25  
Old 06-22-2016, 06:10 PM
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Sweet it's only 5am and already learnt something for the day 👍
Next questions what's better or should I say more suitable
A motor with higher rpm and a pump with lower CC
OR A pump with lower rpm with a pump with higher CC
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  #26  
Old 06-23-2016, 06:10 PM
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Doing a quick mock up last night before I buy anything and trying to picture everything laying it out with tape etc.
the 36" ram is extremely long I'm worried about the weight specifically at the drive arm end will this cause the drive arm to droop while bending which will cause the die to start bending out of square only thing I can think of doing is making like a block for the ram case to be supported on as close to the end of the ram ( near the bender pivot) to help support the ram casing anyone have this problem?
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  #27  
Old 06-23-2016, 07:27 PM
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That is all theoretical design work, so if a shorter ram is more appropriate, by all means mount it the way Jay did and make sure it's big enough. You will take a speed penalty.
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  #28  
Old 06-23-2016, 08:58 PM
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I thought about the weight of the ram twisting the frame which is why I'm making it the way I am. The lower mounting for the ram is going to be triangulated. If you look at the sketch I put in this thread you will hopefully see what I meant. I should have it tacked together by next weekend so should be able to put a picture up then

Adam
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  #29  
Old 06-23-2016, 09:02 PM
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Yea I seen that scratch that got me thinking about the weight factor I'll be interested to see the finished product 👍
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  #30  
Old 06-24-2016, 05:09 AM
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Trying my maths out bare with me.
A USA page (northern tool)
http://m.northerntool.com/products/s...?hotline=false
I have been reading a lot of guys are using this set up with the 36x3 ram and say it works really well
1 hp @ 3450rpm 1.25gpm/4.73letres
4.73x1000/3450 = 1.37CC
SO here in Aus I can't buy that motor
Best I can get is 1 Hp that spins at 2800rpm
So 4.73lpm X 1000/2800 = 1.68cc
So does that mean I need to find a 1.68cc hydraulic pump to
Get the same flow/speed from my 2800rpm motor??

Question 2 what's the difference between a 1hp motor that spins at 2800rpm and a 3hp motor that spins at 2800rpm

Question 3
Would a lower rpm motor ie 1800rpm coupled to a higher Cc pump ie 2.62cc
Be better then the set up above with the higher speed motor if they are both putting out 4.73lpm surely there is something else to it?
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  #31  
Old 06-24-2016, 11:57 AM
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For question 1, per the specs for that hydraulic unit, the pump displacement is 1.59cc. That works out to 5.49lpm or 1.45gpm (us) / 1.21gpm (imperial). I'm guessing the 1-1/4gpm spec provided for the pump is based on the imperial gpm. I would trust the 5.49lpm if you want to replicate that flow rate.

If your motor spins at 2,800rpm, you need 5.49 x 1000/2800 = 1.96cc pump to get the same flow rate.

A simpler way to scale this is based on the pump displacement and motor speeds: 1.59 x 3450/2800 = 1.96cc

For question 2, the difference between a 1hp motor and a 3hp motor spinning at the same speed is that the 3hp motor will be able to produce 3x more shaft torque at that speed. This means the 3hp motor can produce more hydraulic pressure for a given pump flow rate or can support a higher flow rate pump for a given pressure. If the system is not sized properly, the motor will stall or draw excess current and burn itself up.

For question 3, typically I would prefer the slower (more poles) motor with the higher displacement pump, because wear and noise will be lower.
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  #32  
Old 06-24-2016, 12:44 PM
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Just to expand on the motor speed topic, ac motors are commonly available in 2 pole or 4 pole versions. The number of poles describes how the motor is wound and the no-load speed of the motor is directly determined by the number of poles and the supply frequency. At no load, a motor will run at 2 * frequency * 60 / # of poles.

In the US, we typically get power at 60hz while outside of the US, 50hz is more common. Using the formula above, the typical speeds would be:

Poles : Speed US 60hz / Outside US 50hz
2 : 3600 / 3000 rpm
4: 1800 / 1500 rpm

When an AC motor is loaded, it "slips" to a lower speed, which is why you see slightly lower rated speeds. It is typical for a a small 1hp motor to slip around 5%, which is why the motor you linked to on the Northern Tool site is specified at 3,450rpm instead of 3,600.

The upfront cost of a 4 pole motor is generally higher than a 2 pole motor because it is more involved to manufacture and takes more materials. They can sometimes be larger or heavier than their 2 pole counterpart, although for smaller (1hp) motors the same motor casing is often used for both versions resulting in no size difference. Long term, a 4pole motor may pay for itself in terms of maintenance and repair since it runs at a lower speed.

For an application like a tube bender that is used intermittently, you may never see a return on investment paying more for a slower 4 pole motor since chances are even running everything at faster 2 pole speeds, your machine life is probably going to still be a lot higher than you'll need - it will probably outlast you anyway - so if the cost of the motor is significantly different between the 2 and 4 pole version, you may want to just design for the faster 2 pole version.

If you ran a business where you had pumps and motors all over the place running more-or-less continuously, you would want to put this under a finer analysis. I should note this is barely scratching the surface of motor selection/design and there is technically a lot more to it.
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Last edited by TheBandit; 06-24-2016 at 02:20 PM.
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  #33  
Old 06-25-2016, 05:47 AM
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Sorry I've just flicked through this thread but just to add my experience,I would oversize the motor,Im no expert on hydraulics and even less on electrics but when doing my hydro conversion I tried to calculate and in the end I just winged it,it didn't work first time,my pump was too big..i can't remember my final pump size (can check if any help)but my motor is 5hp ( what I had available)and 2850 rpm..my Cyl is only 40 mm,it's very fast,No way I could use full flow..i used stock mount points on my JD,to clear larger dies would have Made my bender very bulky so I opted to repin when necessary,rarely ever need
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  #34  
Old 06-25-2016, 07:01 PM
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3.79l to a us gallon, 4.55l to an imperial gallon, just be aware which you use when checking flow rates.......
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  #35  
Old 06-25-2016, 07:03 PM
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was to slow in getting my reply, thanks guys for noting volumetric differences
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  #36  
Old 06-25-2016, 09:16 PM
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When your looking at specs how do you know if it's in us gallons or imperial?
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