Automated Hill mk3 pump

[wyz2285]

Well, because I'm lazy as f**k so charging my paintball tank took all the fun of airsoft out.
I decided to make automated "thing" to drive the pump, as shown in picture.
Datas: Distance between pump fully extended-retracted is 44cm, so the length of that arm link to the pumps is 28cm, 22cm between the two axis; The wheel diameter is 30cm, the wheel on the electric motor is 5cm diameter (not shown, because I haven't decided what kind of motor I need).
The arm has a thickness of 2cm, the triangular support has a thickness of 3cm and so does the wheel. I'm planing on use aluminium for everything.
So for the pump to reach 3000 psi my own weight(60+-) is not enough, I've to take a little "jump" to push it, so about 100 kg to push it down I think?
My questions are: will the structure be able to hold it? I see some distortions Also what kind of electric motor do I need (what are the specifications I need to know, like torque, rpm etc)? It doesn't have to go fast, 10 cycle per minute is perfectly fine.

[Anatine Duo]

I like what you are thinking.

Have you considered the problem of heat?

With a few pulleys you can reach the force you need but by the time it's all done you might have been better off building a short stroke pump from scratch, something like the shoebox compressor.

Can you add weights to your pump handle? That way you share the manual work between pushing and pulling... may void warranty

[wyz2285]

Yeah, add a little fan would solve the heat problem.
I know just few pulleys it maybe technically strong enough to pump, but my concern is if the structure is strong enough to hold together.
The pump is 3 stage, kind hard to make something like that, I can avoid all these pistons and check valves.
The pumps is 3 stage, you compress air by both pulling and pushing, so add weight won't solve the problem.

[jackssmirkingrevenge]

As a younger person I had dreamt of doing this with a shock pump. As previously stated, heat is the biggest issue you have to contend with.

The FX pump is similar to what you want to do: http://www.airgunsofarizona.com/Review% ... ylord.html

I believe it circulates oil around a jacket in the pump body, even so the unfortunately named reviewer above was giving it time to cool off.

[wyz2285]

Well if the shoebox compressor was still for sell I'd buy one, but it's not.
Time is not my problem, physical effort is I don't mind shutting it off every 5min to let it cool.

[mobile chernobyl]

Straddle the pump inbetween 2 half-weight flywheels to rid yourself of the moment arm created on the side right now if you can. That will make balancing out the forces much easier. Use some heat sinking on the compression chamber of the pump and the high pressure line out if you can as well to alleviate the heat build up which will be inevitable when compressing air.

Take this air line for example:
http://www.ebay.com/itm/like/250396074807?lpid=82

Or just go the cheap route and submerge the pump/section of the output line in water bath haha - just make sure to give the pump a snorkel!

[Anatine Duo]

http://www.shoeboxcompressor.com/

I think this company is still running, and you can get 4500psi

[wyz2285]

I'd rather not spent an extra 600 euro on a compressor that is obviously overpriced and left a 300 euro pump which is still in excellent condition.
@mobile chernobyl can you draw a simple diagram? I'm not sure I got the right idea :s

[jackssmirkingrevenge]

I knew this discussion was familiar

[wyz2285]

Oh yeah, basically I got lazier and decided to "simply" the pump part, also the hill pump is faster than the shoebox compressor. Anyway, how am I going to decide what kind of motor I need?

[wyz2285]

[youtube][/youtube]
&
[youtube][/youtube]
These are nice, I' trying to make a copy. The motors used obviously have a gearbox which I'm having a hard time finding one. Got the idea of using a electric hoists which has low rpm and high torque.
Now the hoist has the cable wheel with a diameter of 10-15 cm while I need 44cm Dia to swing the pump. The model is said to have 250 kg lifting capacity so since the arm is about 3 times longer the force is 3 times lower right?

[Technician1002]

For the pressure you are talking about, there are several issues.
1 Air compresses. Sort of a no brainer, but hang on.
2 All piston pumps have some "dead" space between the piston and valves
3 Displacement at high pressure is high force.

In regards to 1 and 2, if the output is 10X the input in absolute pressure, then everything compressed will just reach the pressure to balance the output valve if your dead space is 1/10th the cylinder volume. This air won't exit the valve but just re-expand. So in absolute pressure, 1 ATM at sea level is only 14.7 PSI. 10 X that is just under 150 PSI.

Scaling it up to 1500 output means your dead space has to be better than 100:1 ratio as at 100:1 all your pumping effort will not produce any output out the check valve as it is just enough to balance it.

Using a long stroke pump will either pump very little, or will suffer from huge forces.

Recommendation is a multi stage pump, either a 2 or 3 stage. Each stage can be only a 10X compression ratio with good efficiency. Remember each stage will have 1/10th the volume of the prior stage and still require the same power to operate each stage.

A 3 stage pump typically goes from 1 ATM intake, 150 PSI out at 10X first stage, then 150PSI to 1500 PSI on the 2nd stage, then a max of 15,000PSI off the third stage. This is the normal arrangement for air packs for EMT or SCUBA. As mentioned before, cooling between stages is a must.

[Brian the brain]

I suggest submerging the entire tube and valve assembly in water.

Water-cool that badboy!

I remember my 80 bar pump getting so hot it would burn my hands....that is...before it broke and cracked my upper jaw..

Wich my dentist deemed plausible by the nerve-damage still visible on xray ( last week)
As the bone heals without a mark ( after time) he could not verify it 100% but he said it was very likely...

[wyz2285]

Well I already own a Hill mk2 3stage pump, I just want to make the process automatic.
Can't submerge it in water because the pump will rust. I'm thinking of install a big ass fan and stop every 5 min.

[mobile chernobyl]

Use soft 1/4" or 3/8" copper tubing and wrap it as tightly around the pump body as you can - run a recirculating water loop through this coil! The copper will allow the best heat xfer rate of affordable materials, and if you are able to either get a dense coil, or for a less dense coil, as you wrap it tamp it with a rubber mallet to form it to the pump body - being careful not to damage the body of course - you'll have great results - it's not cooling the internal piston however which could still be an issue.