Hydraulic pump to weed eater platform

[Brad_Blazer]

Nitrogen is an interesting idea. Might have to design for shock prevention since a compressible flluid will tend to slam the jaw shut for example when the last part of the cut is a fracture. Also, I think that type of unit typically operates at 10,000psi so even at reduced load you wouldn't get much useful work out of a cylinder of N2. A better combination might be a CO2 cylinder powering an air/hydraulic pump.

I think a weedeater engine has plenty of horsepower - many times what that battery unit has. This can even be done with hand power. The OP's idea can certainly be made to work and it certainly lacks novely. It will be expensive compared to a single acting piston-powered-spring return deal. I imagine the 10,000psi gear pump will be as expensive as everything else combined. I actually have one on my junk shelf - too bad the OP doesn't deserve it.

Check out these offerings from you-know who:
- Harbor Freight Tools - Quality Tools at the Lowest Prices
- Harbor Freight Tools - Quality Tools at the Lowest Prices
Add a CO2 power kit from Lowes, a hose and a stick and Voila! A $300 porta-cutter on a stick!
Kobalt at Lowe's: Portable Compressed CO2 Regulator

Oh yeah, here are the formulas.
Force = Pressure *Area
Power = Force*distance/Time
For units go here:
Units of Measurement

 

[J_J]

What is 12 mm in inch's?

 

[Egon]

1" = 2.54cm.

 

[J_J]

That did not help at all. I found it here.

Convert MM To Inches Conversion Tool

 

[Egon]

Well heck, 1cm. = 10mm.

 

[Soundguy]

I think a weedeater engine has plenty of horsepower - many times what that battery unit has.

meaningless comparison without the specifics of both pieces of equipment

soundguy

 

[63DH8]

I am looking for all the information I can gather form experts such as you as to the development of a design which I will describe. I have a need for a hydra operation that operates a scisser type mechanical device that will shear 1/2 inch bolts or 1/2 inch rebarr. This device would be best designed by attaching a hydra pump onto a weed eater and engine platform. Operations would be for a person to power the pump by running the engine which produces fluid power to a sisser mechanism located about 6 feet from the head/pump. One blade would be stationary and the other stroke operational. Of course an expandable coil hose assembly would couple the pump and scisser/shear. I would expect the shear to opeate with either a pull or push piston and a trigger switch would operate the function device. Though I am a BSEE I have very very limited knowledge of hyra and would appreciate all the design help you can support me with, even if it is send me to another site. Just pls give me some direction.

Needed to assemble a prototype unit:
1) Estimated hp for engine and pump.
2) Trigger/switch ideas.
3) Scisser mech piston or other operational device.
4) Fluid reservoir container and size.
5) Formula/s used to estimate the above.

The way hydraulic systems are designed is you take the work (how much required force you need), mate that with the appropriate sized cylinder(s). You may have to compromise between diameter and length because, the larger the diameter, more force is delivered. However, you may not have the space or room for a four foot diameter hydraulic cylinder.

Next you have to look at how much time you have to do the required work. This is where a smaller diameter cylinder comes in. It'll extend and contract faster than a larger diameter cylinder. However, a small diameter cylinder may not have the required force to do the job. Mate this information to the pump size. If you can afford to have a stationary pump, size isn't as much a consideration. If you have to carry the pump, you're not going to want to carry a 50lb pump. A large cylinder will do the work, but it'll take next to forever to do the work. Remember, hydraulics work on the principle of ratios. Small displacement pump and larger volume in the cylinder multiplies the power of the motor.

Now the pump. The rating on a pump is pretty much it. If the tag says the pump is rated at 2000rpm/5gpm, you're not going to get much more than 5gpm out of the pump by spinning it faster. Sure, you may get another half or so gallon per minute from the pump by increasing the speed by another 500-1000rpm, but that's really about it. You can flow only so much fluid through the ports.

I'll give you a tip; The manufacturers have handbooks that mate pumps with cylinder sizes to how much force you need. Figure how much force is needed to do the work you're envisioning and go from there. If I were you, I'd consider multiple links for leverage so I wouldn't have to carry the required weight of the hydraulics to do the work.

 

[Soundguy]

on a positive displacement pump.. output will be ratio tied to rpm.. however if you hav inlet or outlet restrictions, you will get cavitation or backpressures issues.

soundguy

 

[J_J]

Well heck, 1cm. = 10mm.

You still did not answer my question, and please don't answer or reference any of my post.

I am seriously thinking of adding you to my ignore list.

 

[J_J]

63DH8,

How large do you think that rebar cutter is from HF. It uses 10,000 psi, and that can be obtained from just about any hand pump, or one of the air motor driven hydraulic pumps. That is probably a carbide head on there, and cutter is rated at 12 mm, or.47 in, a little smaller than 1/2 in. If this were mounted on a solid line capable of 10,000 psi he could reach to whatever distance he wanted. If he is dead set on a weed eater engine, I just don't know. Probably the nitrogen would work. We still don't know the full extent of what he is trying to do. The rebar may be inside a pile of cement/rebar rubble. I have something that would cut just about anything, and that is the jet rods, or Exothermic/Slice rods. just need oxygen.