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Which Eccentric Mechanism to Choose for My Tool?

09/29/2017 2:20 AM

Hi folks, I am using a hand driven pump like the yellow one on the picture . I want to use an engine for that pump instead of using my hands and a pump arm.

I will disassamble the long arm from my yellow pump and will want to transmit engine power to the piston.

Engine power is 0.6 kW

rotation of my engine is 50 per minute.

Shaft on the engine will need to be able to rotate under load approx 400 kG ( that is what the maximum weight needed to be put on the piston)

will the engine 0.4 kW ( 50 rpm) be strong enough for that job ?

Can you please advice which way is best for transmission of the engine power to the piston ? I have few example below, but maybe there is a better way ?

THank you for help !

Frank

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#1

Re: Which eccentric mechanism to choose for my tool ?

09/29/2017 2:46 AM

Your whole approach is completely ridiculous. Perhaps the best bet is a simple vane pump, but that would depend on your unspecified pressure requirement.

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#30
In reply to #1

Re: Which eccentric mechanism to choose for my tool ?

09/30/2017 3:52 AM

I once had 2 students of University Twente, who boroughed a similar hydraulic testpump from Sulzer Pumps, bringing back the pump and complaining that the capacity was too low as they had been pumping nearly 8 hrs to fill the tank they wanted to test, I advised them to fill the cavity with a garden hose next time and use the handpump for the last few strokes. If your reason to motorise your Parker pump is the same.....buy a garden hose and use elbow steam on the pump.

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#2

Re: Which eccentric mechanism to choose for my tool ?

09/29/2017 2:50 AM

I would go with a pump jack design...

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#3

Re: Which eccentric mechanism to choose for my tool ?

09/29/2017 3:02 AM

I want to keep my hand pump, I dont want to buy new electric pump

I achive 500 bars on that pump and buying automatic pump that strong would be expesive and I guess it would be noisy to work with.

As I said I am using up to 500 bars which means I press the piston with approx 400 kG

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#4
In reply to #3

Re: Which eccentric mechanism to choose for my tool ?

09/29/2017 3:21 AM

How do you do that? Are you the Incredible Bulk?

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#5
In reply to #4

Re: Which eccentric mechanism to choose for my tool ?

09/29/2017 3:42 AM

there is a lever on the pump. It helps you know :)

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#6
In reply to #5

Re: Which eccentric mechanism to choose for my tool ?

09/29/2017 3:52 AM

That's really, really dumb. (Just so you know.)

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#7
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Re: Which eccentric mechanism to choose for my tool ?

09/29/2017 4:03 AM

I have a proper and simple hand pomp that is perfect for my job, I just want to improve it with a small cost, and in case anything broke, I can quicky back to my hand power again.

And you instead of simple advice ( if you able to give one ) give a stupid comments and advice me to buy some other tools that I dont want....

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#8

Re: Which eccentric mechanism to choose for my tool ?

09/29/2017 5:11 AM

Don't be silly. KISS.

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#49
In reply to #8

Re: Which eccentric mechanism to choose for my tool ?

09/30/2017 11:15 PM

Since it's a pumping motion (mostly pushing down), nice biceps aren't good. Well, maybe good to look at, but we need something that pushes down, not pulls up. Pecs, not biceps!

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#9

Re: Which eccentric mechanism to choose for my tool ?

09/29/2017 7:51 AM

A motor-powered hydraulic test pump for pressure vessels? How absurd.

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#10

Re: Which eccentric mechanism to choose for my tool ?

09/29/2017 8:29 AM

Really?,..

I think you should instead think about it,... look for alternatives... and think about it some more....

the one below is powered pneumatically.

I just read PWSlack's post... its to test pressure vessels?...

at what pressure?

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#48
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Re: Which eccentric mechanism to choose for my tool ?

09/30/2017 11:09 PM

I'd recommend the same thing, but he doesn't have enough money to buy one of these. And he's in Germany and I don't think they have HFT there.

I have a solution for him, but he needs to answer a few questions I asked.

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#11

Re: Which eccentric mechanism to choose for my tool ?

09/29/2017 9:14 AM

Since you don't seem to grasp what is going on here, allow me to condense your proposal to its fundamental essence.

  • I have a great idea that's cheaper and better than anything trained engineers have put onto the market. I am not sure how to achieve this brilliant idea. I'll ask for some free engineering advice from an engineering forum.

I call this reoccurring request the "fallacy of ignorant enthusiasm."

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#12

Re: Which eccentric mechanism to choose for my tool ?

09/29/2017 9:23 AM

Really folks I dont understand why you think it is absurd etc etc.

I also dont know how come one of you came up with the idea that it is some kind of pump to test pump for pressure vessels ( or whatever you meant to )

Maybe its my English....but I am pretty sure I explained it in the first post...

HOW TO TRANSFER rotating power from the engine to the piston in my pump.

I even put few examples with the pictures so you could refer to and help me to choose on of them.

I dont claim that I have better idea than trained engineers have put onto the market.

BUT I said, I have already my tool, that I dont want to throw away but instead of, I want to improve. It will work for me. I will send you photos when its finished and you will have a great laugh ;)

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#16
In reply to #12

Re: Which eccentric mechanism to choose for my tool ?

09/29/2017 9:46 AM

Really folks I dont understand why you think it is absurd etc etc.

to answer that, the best what I can explain it... "you don't know, what you don't know".

You're way over complicating this.

It could be a language misunderstanding,... but your graphics may says a lot that it isn't.

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#19
In reply to #12

Re: Which eccentric mechanism to choose for my tool ?

09/29/2017 10:08 AM

Your easiest approach to get your motor to work will be a large cam on the motor. Are sure dead sure you want 50/minute? By gearing down a higher speed motor, you obviously already should know you have a force (torque) multiplier in hand.

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#13

Re: Which eccentric mechanism to choose for my tool ?

09/29/2017 9:29 AM

Hydraulic power pack. Most supply houses will have them. This is one from Harbor Freight. You want to be careful of choosing one with the proper displacement for the application. You do not want the cylinder to extend too quickly. And has a pressure setting releif valve. You do not want to the power pack to be able to produce pressure over the working limits of the cylinder.

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#14
In reply to #13

Re: Which eccentric mechanism to choose for my tool ?

09/29/2017 9:37 AM

Hydraulic power pack. How much that cost with the power of 700 bar, is that silent ? No its not.

That s why I dont want new tool, new machine, I am happy with my 700 bar hand hydraulic pomp and I just want to improve it with engine.

why is that so strange for you folks ?

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#15
In reply to #14

Re: Which eccentric mechanism to choose for my tool ?

09/29/2017 9:43 AM

Because the purpose of the existing pump has been withheld from the forum. No-one would sanction the conversion of a pressure test pump, because that's what it looks like, to power operation without some sort of device available to trip it off once a limit has been reached. So it's not just a case of coupling up a motor and standing back, because in such an arrangement, something will burst before the pump gets shut off.

And if it is doing something else, then there are better ways of doing it, with different styles of pump.

So the quest in the original post looks currently like some great folly to the onlookers.

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#17

Re: Which eccentric mechanism to choose for my tool ?

09/29/2017 9:50 AM

Rotation speed w = 50 rpm = 5/6 rps = 2*pi*(5/6) = 5.23 radians per second

Power = 0.4 kW = 295 ft lb/sec

Torque = Power/w = 295/5.23 = 56.3 ft lb

Force = 400 KG = 880 lb

Radius = Torque/Force = 0.07 ft = .84 inches

So, if your pump stroke is less 2 x Radius, you should have enough power. (From the looks of the picture, it looks OK)

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#18

Re: Which eccentric mechanism to choose for my tool ?

09/29/2017 10:04 AM

Keep the hand pump around and unmolested for when you need it, and make a new pump that is electric motor driven, at the correct speed and torque required.

You did not specify the fluid being pumped (which could be lube grease, oil, diesel, or even water), the rate of pumping desired, or the network pressure rating.

Can't answer other than say, "buy a new pump", until you fork over the information.

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#20

Re: Which eccentric mechanism to choose for my tool ?

09/29/2017 10:14 AM

I did gave the information in the first post.

I have an engine 50 rpm. it's 0.4 kW and it needs to be able to press the piston with approx 400 kG

All I need is an advice how to change rotating movement to a back and forward movement in an easy and efficent way.

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#21
In reply to #20

Re: Which eccentric mechanism to choose for my tool ?

09/29/2017 10:23 AM

I suppose the "easiest" way would be an output disc on the motor shaft, with a Pittman arm attached, and the Pittman would operate the pump plunger back and forth (or up and down, depending on the lie of the land).

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#22

Re: Which Eccentric Mechanism to Choose for My Tool ?

09/29/2017 2:09 PM

Is this homework? A thought exercise? An interview question?

If you have an ACTUAL application with an actual purpose, then please provide some useful information/requirement.

"will the engine 0.4 kW ( 50 rpm) be strong enough for that job"? No one can answer this question with the dearth of information you provide. The design of the arm and the load must be known.

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#23
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Re: Which Eccentric Mechanism to Choose for My Tool ?

09/29/2017 2:22 PM

"will the engine 0.4 kW ( 50 rpm) be strong enough for that job"?

I meant "will it be enough to rotate 400 kG"

not my "job" ;)

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#24
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Re: Which Eccentric Mechanism to Choose for My Tool ?

09/29/2017 2:43 PM

You are not ROTATING 400kG.

If what you said is correct, you will need to apply about 400 kG force to the piston/handle/fluid (another unknown) for about 1/2 the time. The upstroke force will be minimal.

Just buy a pump!

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#25
In reply to #23

Re: Which Eccentric Mechanism to Choose for My Tool ?

09/29/2017 3:02 PM

People have repeatedly asked you for more information. You seem to understand how a lever works. Yet, none of your sketches include any dimensions at all.

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#26
In reply to #23

Re: Which Eccentric Mechanism to Choose for My Tool ?

09/29/2017 4:21 PM

If it isn't your job, then who's job really, is it?

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#55
In reply to #26

Re: Which Eccentric Mechanism to Choose for My Tool ?

10/02/2017 4:00 AM

who's whose

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#56
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Re: Which Eccentric Mechanism to Choose for My Tool ?

10/02/2017 5:05 AM

How fast to you want it to pump? Direct drive from the motor(/gearbox) shaft, or via a (secondary) gearbox?

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#27

Re: Which Eccentric Mechanism to Choose for My Tool?

09/29/2017 7:28 PM

If you're planning on driving the piston with the motor, realize the forces involved (880 lb). You will need something pretty rugged, jerry-riggin' ain't gunna hack it.

Perhaps you can find a small 1 cyl engine. Remove the cylinder and piston. Connect the connecting rod to your pump piston and drive the engine crankshaft with your motor. You would have to mount the engine housing to your pump secure enough to withstand the forces.

Just an idea.

(Building something that will work might get as expensive as buying a new pump.)

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#28
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Re: Which Eccentric Mechanism to Choose for My Tool?

09/29/2017 7:58 PM

I agree that 880 lb of force somewhere will need proper mounting support. However, with the combined long lever (8:1 ?) of the exampled hand pump version and the lack of any additional length dimensions, I don't trust at all where this 880 lbs of force will reside nor if an even more dangerous force will briefly reside somewhere.

I'm also apprehensive of the 0.4 kW engine. This is a more common size for an electric motor and not an engine. I know 0.54 hp combustion engines exist but...

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#29

Re: Which Eccentric Mechanism to Choose for My Tool?

09/30/2017 1:51 AM

Can you give us a sketch of what the rod end of the piston looks like?

My hydraulic press has a similar looking pump.

If it is the same you need to push and pull the rod end, it is not spring return.

I assume you will remove the handle and drive the piston rod directly.

Lets say you use a connecting rod from the end of the piston - then we need to know the required throw for a complete stroke.

If the other end of the connecting rod is connected to a crank on the (gear) motor, then the throw would be the 2 x the radius of the crank. Reducing the throw of the crank will reduce the torque required, but will also reduce the volume of each stroke.

Basic power calculations

T = HP x 5252/ rpm

400w = 400/756 = .529HP

T = .529 x 5252 / 50 = 55 ftlbs

400kg = 880 lbs

when the crank is at 90 deg to the cylinder it needs to develop 880lbs

Max possible radius of crank to develope 880lbs is then 55/880 x 12in/ft = .75 inches

That would give a 1.5 inch throw.

My pump has a 1 inch throw - therefore set your crank radius to less than .5 inches.

Use a long crank arm or you will severely side load the piston. Suggest at least 6 inches.

Consider using a high pressure hydraulic relief valve, or you could easily damage parts.

Alternatively install a high pressure hydraulic switch that will turn your pump off.

I would use both.

Be sure to use heavy bearings on your crank - it will be "pushing" over 880 lbs - design should be for at least 3000 lbs thrust.

The crank pins should also be sized for about 3000 lbs. Without detailed calculations I would expect the crank pin to be 3/8 grade 8 bolt or larger..

I do not have the background to estimate the rod size so it does not buckle - but would guess around .75 inches diameter.

A motorized pump is going to be very fast compared to hand pumping. There will be no "feel" to a motorized system. Use a momentary push button for the motor run. Be sure to use pressure gauges.

McGyver / Rube Goldberg machines can be fun to build - but the Harbor freight solution is the most practical. You will spend far more on the invention than on a purpose built pump.

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#38
In reply to #29

Re: Which Eccentric Mechanism to Choose for My Tool?

09/30/2017 1:49 PM

McGyver / Rube Goldberg machines can be fun to build - but the Harbor freight solution is the most practical. You will spend far more on the invention than on a purpose built pump.

what is that mean

Harbor freight solution

?

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#42
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Re: Which Eccentric Mechanism to Choose for My Tool?

09/30/2017 7:43 PM

See OzB #13 response.

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#52
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Re: Which Eccentric Mechanism to Choose for My Tool?

10/01/2017 12:46 PM

Harbor Freight is a US distributor of tools, hydraulics, saws - etc - with a lot of off shore knockoffs. Quality can range fro poor to excellent - but buyer be ware.

In our area of Canada we have KMS Tools, Busy Bee Tools, and Princess Auto. There are also various farm supply and tracrtor supply outlets with a wide variety of less expensive parts than the high end industrial suppliers.

You bought a second hand gear motor - I am surprised from a similar local source you cannot buy a small hydraulic power pack.

McGyver was a TV series - when I was a child. It has recently been re-booted with more glitz. McGyver would invent dubious machines and solutions on the fly and do miraculous things with a pen knife, tape, and what ever was lying around. He even welded with a coat hanger and a car battery. Imaginitive, but not necessarily realistic.

Rube Goldberg did cartoon strips with all sorts of imaginative complex machines.

A simple Google of those terms would have given you your answers for these questions.

The math, sample machine, easy machining solution, have all been given to you.

I cannot help you any further short of building it for you, or shipping a hydraulic power pack to you.

You do not appear to want to be helped and cannot accept serious answers .

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#53
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Re: Which Eccentric Mechanism to Choose for My Tool?

10/01/2017 12:52 PM

See post #10 and follow this link

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#54
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Re: Which Eccentric Mechanism to Choose for My Tool?

10/01/2017 12:58 PM

This is a fruitless exercise.

He can't Google to help himself.

I'm not wasting my time anymore.

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#43
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Re: Which Eccentric Mechanism to Choose for My Tool?

09/30/2017 8:24 PM

Doodle of possible fixture. Cam can be made with a shaft of suitable diameter - larger than drive shaft. It should be keyed to your gear motor drive shaft. Drill and ream a clearance hole to match your gear motor shaft - but approximately .5 inch from center of cam. Connecting rod will need to be drilled and reamed to match the cam diameter. Recommend using oillite bronze bushing for durability and replaceability. all bearing surfaces should be polished.

A sturdy frame will need to be made to made to support gear motor, drive assembly, and pump.

This is not a backyard build - it will take a machine shop.

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#31

Re: Which Eccentric Mechanism to Choose for My Tool?

09/30/2017 8:34 AM

I don't think a simple cam (as you've shown) would work at 50 strokes/minute, as the piston would need to return (following the cam profile) within about half a second.

You'd need a linkage which would both push and pull.

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#32
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Re: Which Eccentric Mechanism to Choose for My Tool?

09/30/2017 11:26 AM

Enclose the path of the cam and follower

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#34
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Re: Which Eccentric Mechanism to Choose for My Tool?

09/30/2017 12:16 PM

That's the sort of thing I was driving at.

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#33

Re: Which Eccentric Mechanism to Choose for My Tool?

09/30/2017 11:55 AM

I am having a great time looking

for the solution/ movement that I will be happy to use.

https://www.youtube.com/watch?v=qtnSJ2RtcmQ

https://www.youtube.com/watch?v=5kt1ABLXCBM

https://www.youtube.com/watch?v=DGhcrKCAbVk

btw. my electric engine is 0.65 kW 380V German made .

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#35
In reply to #33

Re: Which Eccentric Mechanism to Choose for My Tool?

09/30/2017 12:21 PM

Usually called a motor, rather than an engine. Engine usually implies combustion, or at least pressure, as the motive principle.

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#45
In reply to #33

Re: Which Eccentric Mechanism to Choose for My Tool?

09/30/2017 11:03 PM

Whoa! You say that your motor uses 380V! Three phase 380VAC? Is this a commercial application? Do they have three phase 380VAC power in homes in Germany?

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#66
In reply to #45

Re: Which Eccentric Mechanism to Choose for My Tool?

10/02/2017 3:53 PM

380 V is not normally installed at homes, but it can be if you wish.

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#57
In reply to #33

Re: Which Eccentric Mechanism to Choose for My Tool?

10/02/2017 9:26 AM

So then you already have the gear-motor. Use a pump jack design, but at 50 rotations per minute, that is still very fast. You need to seriously think about the return stroke, not just the driving stroke of your pump.

Several good points and suggestions have been given to you - go forth, and knock it out. Let us know what you did, with pics and video after.

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#36

Re: Which Eccentric Mechanism to Choose for My Tool?

09/30/2017 1:22 PM

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#37
In reply to #36

Re: Which Eccentric Mechanism to Choose for My Tool?

09/30/2017 1:47 PM

different approch :)

but I already bought the motor...and now its no point to use such a large motor for this.

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#39
In reply to #37

Re: Which Eccentric Mechanism to Choose for My Tool?

09/30/2017 1:58 PM

Why would that need a larger motor?

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#46
In reply to #36

Re: Which Eccentric Mechanism to Choose for My Tool?

09/30/2017 11:05 PM

Looks good, but he wants to get rid of the lever.

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#40

Re: Which Eccentric Mechanism to Choose for My Tool?

09/30/2017 2:36 PM

???

It doesnt need larger, did I say it does ?

It needs smaller, so as I said, it would be a waste of power to use my large motor for this...which obviously needs less power...but the idea of attatching someting to the hand lever is not good for me.

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#41
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Re: Which Eccentric Mechanism to Choose for My Tool?

09/30/2017 3:38 PM

Then how do you expect to move the hand lever?

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#47
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Re: Which Eccentric Mechanism to Choose for My Tool?

09/30/2017 11:07 PM

He's taking the hand lever off and the mechanism will run off the actual pump piston.

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#58
In reply to #40

Re: Which Eccentric Mechanism to Choose for My Tool?

10/02/2017 9:28 AM

Why do you need to remove the hand lever? Space constraint?

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#44

Re: Which Eccentric Mechanism to Choose for My Tool?

09/30/2017 10:51 PM

I am a businessman who did some engineering work years ago. I'd like to take a shot at this idea you have.

First, stick with the KISS principle - this is my first piece of advice.

Second, you have something that works, but you don't like to manually use the pump. You want to improve on it, correct?

Third, you have an electric motor and you'd like to use it to run the pump, correct?

Fourth, you have some pretty accurate specs on the forces needed at the pump and what the motor puts out, correct?

Please confirm the following, to make sure we're on the same page.

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#50
In reply to #44

Re: Which Eccentric Mechanism to Choose for My Tool?

10/01/2017 2:19 AM

YES Autobroker you are coorect. Its all in my VERY FIRST post but still so many people instead of focusing on my question, they even ask me what kind of oil I am using in that pump as it was important to answer the question...my question was which kind of movement to choose.

Now I see I also aked in the first post if the motor 0.4 will be strong enough. That question was not that important as I decided to buy larger motor 0.65 and I am sure it will be far more than enough. Maybe I shouldnt ask that question as most of you focus on that asking for specified details so to be able to calculate that ...thank you anyway. But also me English in engeenering filed is very poor so I dont know much what you talking about sorry....like the example "kiss principle " I had to google :)

BTW. I am still wondering what means McGyver / Rube Goldberg machines can be fun to build - but the Harbor freight solution is the most practical. You will spend far more on the invention than on a purpose built pump.

Harbor freight solution ?

I decide to make it simple like silver example from my first post. Its a following cam.

maybe its not fun to look at as much fun this can be, but easy to make

https://www.youtube.com/watch?time_continue=20&v=qtnSJ2RtcmQ

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#51
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Re: Which Eccentric Mechanism to Choose for My Tool?

10/01/2017 12:20 PM

Silver example will not work as shown - the piston has to be pulled up and pushed down.

If you want the silver example you will need to add a lifting spring on the piston shaft- just like a car valve train.

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#59
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Re: Which Eccentric Mechanism to Choose for My Tool?

10/02/2017 9:37 AM

Here you go: try this, using metal, so it will stand up to the forces, don't forget the gear grease for the rack and pinion:

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#60
In reply to #59

Re: Which Eccentric Mechanism to Choose for My Tool?

10/02/2017 12:13 PM

We must come up with more fancy Rube Goldberg designs. Our suggestions are obviously too simple and inexpensive for the OP to make in his garage.

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#62
In reply to #60

Re: Which Eccentric Mechanism to Choose for My Tool?

10/02/2017 3:28 PM

we can't do that sir,... someone left the gate open and our power supply (pigeon) flew away.

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#65
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Re: Which Eccentric Mechanism to Choose for My Tool?

10/02/2017 3:44 PM

I thought it was the squirrel that got loose.

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#70
In reply to #65

Re: Which Eccentric Mechanism to Choose for My Tool?

10/02/2017 4:49 PM

We got the pigeon to replace the squirrel.

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#71
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Re: Which Eccentric Mechanism to Choose for My Tool?

10/02/2017 4:57 PM

Now the cat can chase the pigeon, land on a lighter that boils water that runs a steam engine that drives the pump. Done!

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#74
In reply to #59

Re: Which Eccentric Mechanism to Choose for My Tool?

10/03/2017 2:40 AM

What type of metal do you recommend. I'm thinking he can make it our of pot metal to keep the price down. He can make a wax mold of the parts, then cast it using a lost wax process. He could make the model out of a metal that melts with an oxygen/propane torch set up - I'm thinking brass.

Then make a sand mold out. Pour the molten pot metal into the mold and he now has a part + a brass sample to make more molds.

Of course he'd have to clean up the pot metal part, but he'd have created the mechanism he needs to make his pump work.

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#75
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Re: Which Eccentric Mechanism to Choose for My Tool?

10/03/2017 9:07 AM

He could use sheet metal, even cut the rack gearing out with tin snips, and layer the sheets together for strength with epoxy to bond them.

Same thing with the pinion.

My personal opinion about this is he has already found a system on the internet that is complete, and is unwilling to spend the cash on it.

I say to OP: yes, go ahead and make your cam, and put the return spring/follower on the pump plunger. He could cut the thing out of thick plywood, sand it lightly, and test his prototype. Then he could take steel sheet metal and band the plywood, and have a more durable cam (until he makes a solid one).

At this point I an running out of "care juice".

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#80
In reply to #75

Re: Which Eccentric Mechanism to Choose for My Tool?

10/04/2017 3:03 AM

Or, he could go to his version of HFT and buy a made in China unit and save himself a lot of work.

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#77
In reply to #74

Re: Which Eccentric Mechanism to Choose for My Tool?

10/03/2017 10:06 AM

Pot metal? Since he wants to bypass the force multiplying devices this mechanism will experience the maximum pressure. I would expect a zinc based pot metal will buckle under stress. On second thought, a strategically placed sacrificial part maybe appropriate.

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#81
In reply to #77

Re: Which Eccentric Mechanism to Choose for My Tool?

10/04/2017 3:09 AM

Follow this logic for a minute:

1. He could remove the lever on the original pump.

2. He would make a new lever out of titanium or maybe a nice stainless steel. Heck, he could even use a piece of galvanized pipe or a piece of copper pipe filled with concrete. Something different from the original handle.

3. The pot metal mechanism would be hooked up to the end of the lever.

4. The other end of the pot metal mechanism would be hooked up to the motor.

5. With a nice lever arm, the pot metal part won't have excessive force on it and it won't break.

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#86
In reply to #81

Re: Which Eccentric Mechanism to Choose for My Tool?

10/06/2017 4:11 PM

I see you have some very intersiting ideas I wish I knew what you talking about :( myenglish bro...

what is pot metal mechanizm ?

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#89
In reply to #86

Re: Which Eccentric Mechanism to Choose for My Tool?

10/08/2017 2:58 PM

Pot metal is a cheap, light weight material that is used for quick, low temp castings. A zinc alloy that isn't very durable, but you can make many copies for a low price. You simply make the mold, then you can pour multiple copies and when they break, you just swap it out with a new one.

If you wanted to spend more money, I'd recommend switching from pot metal to brass. Your cost would be higher, but you'd have something much more durable.

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#82
In reply to #77

Re: Which Eccentric Mechanism to Choose for My Tool?

10/04/2017 3:15 AM

To save money, he could make the cabinet into a three pole unit and take one of the vertical poles out and use it as his lever arm. He could carve the wax using the diameter of the pole as his guide. The cast the piece using a lost wax technique via a plaster cast, then melt the brass and when the mold is hot enough, he can pour the molten brass into the mold. Then he could use the brass model and make sand molds for casting.

It's very easy and it would work great.

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#73
In reply to #50

Re: Which Eccentric Mechanism to Choose for My Tool?

10/03/2017 2:32 AM

You seem like a smart man, who knows about design and proper scientific analysis. I want you to think about the mechanism for a minute and the power the motor puts out.

1. Your pump has a lever arm that allows a man to use the pump with his arm.

2. The mechanics (forces) on the arm are such that the moment produces a mechanical advantage - all with the small force from a man's arm.

3. I think you had come up with the answer yourself, but you didn't realize it. The power of the motor doesn't matter that much. Heck, it can be even less than the power a man's arm has. Here's why. You can use other levers, cogs, eccentrics, gears, etc to insure that the motor will move the pump.

4. So, to use our KISS principle, make the mechanism as simple as possible, OR purchase something off the shelf that works.

5. If you have an existing mechanism that multiplies force, then you can modify it to work with your pump. This is what McGuyver was famous for.

6. If you don't have anything and you have to build something from scratch, it may be in your best interest to purchase an all in one unit from a place like Harbor Freight.

I hope this helps.

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#61

Re: Which Eccentric Mechanism to Choose for My Tool?

10/02/2017 3:24 PM

I think I will stick to this one.

Cam made of steel 1 inch thick,

follower made of Polyoxymethylene (POM) , ( slick material )

and a spring on my piston.

couldnt be simplier :P

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#63
In reply to #61

Re: Which Eccentric Mechanism to Choose for My Tool?

10/02/2017 3:28 PM

Well there you go? What exactly are you pumping up?

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#64
In reply to #63

Re: Which Eccentric Mechanism to Choose for My Tool?

10/02/2017 3:42 PM

press is what I am pumping. I make embossed plates.

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#67
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Re: Which Eccentric Mechanism to Choose for My Tool?

10/02/2017 4:12 PM

I hope your hydraulic design has either a pressure relief valve to bypass fluid or a (pressure?) limit switch to turn this 0.5 HP pump OFF. Most human arms have enough sense to know when to stop pumping. Your motor has no sense at all.

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#68
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Re: Which Eccentric Mechanism to Choose for My Tool?

10/02/2017 4:41 PM

yes I have a relief valve in my pump, I also have a clock that shows me what preassure is already pupmped . I will have start / stop button as well....

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#69
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Re: Which Eccentric Mechanism to Choose for My Tool?

10/02/2017 4:47 PM

the oil resrvoir on your pump is very small. With a motor driven pump it will deplete it in seconds. I suggest you may only want a momentary run button - dead man style - you release and it stops.

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#72
In reply to #69

Re: Which Eccentric Mechanism to Choose for My Tool?

10/02/2017 4:57 PM

I need approx 20-30 moves to get 400-500 bars. that not that fast to be worry about...

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#76
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Re: Which Eccentric Mechanism to Choose for My Tool?

10/03/2017 9:25 AM

So with a 50 RPM motor and no gear reduction you will be at maximum pressure in well under a minute if all goes as planned. A non-latching switch seems like the way to go.

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#78
In reply to #76

Re: Which Eccentric Mechanism to Choose for My Tool?

10/03/2017 12:03 PM

This is precisely the type of equipment where a foot switch, and maybe a separate switch for pressure release are important safety features, or even incorporate pressure release into the operation of the foot switch.

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#79

Re: Which Eccentric Mechanism to Choose for My Tool?

10/03/2017 4:04 PM

all set before made and connection

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#83

Re: Which Eccentric Mechanism to Choose for My Tool?

10/06/2017 3:04 PM

I was wrong when I estimate how many rpm I need. 50 is not enough so I swap the motor for 0.75 kW and 125 rpm.

Sometimes I need to push hard as much as 500 or 600 bar so I am not sure if motor 0.75 kW and speed of 125 rpm will do to push 20mm piston so I am thinking of making a two gear follower cam ;) so it would be shorter travel like 12 mm instead of 20 mm .

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#84
In reply to #83

Re: Which Eccentric Mechanism to Choose for My Tool?

10/06/2017 3:13 PM

Half the stoke at twice the speed gives you the same flow.

Why not buy a purpose built pump this time?

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#85
In reply to #84

Re: Which Eccentric Mechanism to Choose for My Tool?

10/06/2017 3:33 PM

why people still telling me to buy another pump LOL

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#87
In reply to #83

Re: Which Eccentric Mechanism to Choose for My Tool?

10/06/2017 4:21 PM

self-defeating arguments, will have you chasing your tail.

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#88
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Re: Which Eccentric Mechanism to Choose for My Tool?

10/07/2017 8:24 AM

MORE POWER

That must work, shouldn't it?

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