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BBGun Bob · Veteran Member

http://www.network54.com/Forum/79574/thread/1237007498/Tired+of+Hand-pumping--

At $675 I don't see a lot of people buying this thing when you still have to buy a $220 FX pump.This guy must be smoking crack to ask that much money for that thing.

BBGun Bob

dummyracer36 · Senior Member

for that price i would expect something less.... utilitarian looking. and personally, i dont like the way the pump moves, i would have done it a fixed pump and used a 2 piece connecting rod. but hey, if it works, but not for that much $$$$

rsterne · Moderator

By the looks of the TWO belt tensioners on the second belt, he hasn't figured out that you can't reliably use that much reduction in one stage with V-belts.... there isn't enough friction area on the smaller pulley.... Rolling Eyes

Yeah, the price is pretty much a joke.... but I would imagine it took him quite a while to fabricate it.... Laughing

Bob

Jaxom · Senior Member

I'd use a smaller motor, high torque, low rpm, direct drive to the pully. Do away with the belt arrangment all together. And like dr says, two piece connecting rods. Keep the pump stationary.

BBGun Bob · Veteran Member

better suggestion on how they/you would build such a pump.or how he should have built it.Which is fine with me!
But the bottom line is there is only guy that has actually built one of his own design and has gone as far as to sell a kit.And it works!!
All of you can nit-pick it apart all you want but until you do a better job and build your own working model DO ME A FAVOR ,,And just shut the F*&#k up.

Yes his price is to high,,and I'll never buy one because of that reason and only that reason,However I have to give the man credit where credit is due,he has built a working model !!! HIS WAY!!What have you built???
You guys remind me of Rush(Boss) Limbaugh never did a friggin thing but spew a bunch of conservative crap and thinks he is God's gift to the Republican Party.

Thanks I'm Done. Page #2
And now you know why I don't come here very much anymore.

BBGun Bob

Alstone · Moderator & Site Supporter

The only problem with a two piece connecting rod is that for part of its stroke it is exerting pressure at and angle to the pump, and this will cause wear on the bushes of the pump, unless the joint between the connecting rod is supported in its own sliding bushes, such as the connecting rods on a steam locomotive, and this arrangement would add cost to the project.

This guy as kept it simple and it works.

Al

kanyon · Silver Status Member

Jaxom · Senior Member

Actually bob, I think you just a bit wrong. Don't get mad, just hear me out in from my position. I like this guy's idea. It gave me many of my own. I don't have a scuba shop near by and I'm not exactilly the most fit person on the planet to make 180 some odd strokes it takes to fill a tank.

The other option is to buy a pump. And so far the only one I've seen that can fill hpa tanks is one sold by AoA. And has a hefty price tag of around $1800.

I did a bit of research on some of the parts that I was talking about in my last comment. Yet again I wish I had a cad program and knew how to use it!

Alstone,

To adress your concernts about the pump's rod sliding at angle... As I've already mentioned, I'd use a linear "pillow mount" bearing. Perhaps even two just to make sure the pump's shaft stays straight. In addition I'd drill a few holes in the "foot pads" of the pump so I could driectly bolt it down. Then add a brace or two over the pump to the frame assembly. This would make the pump VERY secure.

For the connecting rods you could use a mixture of female and male "spherical rod ends". Conviently these come in threaded and non threaded. Once you've spun the handle that comes with the pump off, just have to determine how it was orginally threaded and then just order the right rod end for it.

Kanyon,

I just had a simlar conversation over at a forum that's related to hobby foundries. In order to do quality sand casting one can buy, or or make a sand mueller. This is basically a drum that rotates very slowly for extened periods of time mixing sand, oil and other additives to make quality castings. For a home brewed one, you can use a scavanged washing machine motor, or like really nice one that someone showed us, he bought a geared replacement motor for a concrete mixer off of ebay for $50. It runs on 115v 20amp circut at 65rpm.

About all that I would need to do now is figure out how long to make the connecting rod. And that I really couldn't say until I had all the parts on hand and then did a partial assembly, and then I could calculate how much angle or box steel I'd need to weld this all up.

If anyone else is interested, you can see examples of the parts I've mentioned if you google for Grainger and then do a parts search for "Sphearical rod ends" or "linear bearings pillow block". And you can see where I'm going with this. The prices are actually very reasonable. One pillow block for 1/2 rod will run $35 and the rod ends run around $15 each.

Lastly, it's a given that Murphy's law will apply to anything "fun". Just when I've gotten a tank connected and the pump running, is right when something will happen. One could easily forget about the pump filling tank as you go run stop a child doing something they shouldn't. A wife doing something she shouldn't, or parent doing some they shouldn't! LOL. Thing is I'd be concerned about not having some type of emerency shut off once the tank reaches pressure.

Bob, again for the record, I think this guy has a good idea. But like many idea's it can be improved upon. Even my concept on how to build this could be improved upon. And I would hope if there's a design flaw or perhaps a suggestion on how to make one better, please do tell me! I also give the guy credit for attempting to make something to sell.

In as much that I am a welder and I do want to convert my crosman to being a HPA ag, and I don't want to spend $1800 for an off the shelf mechanical pump, I do belive this project for me has jumped to the top of my list of welding projects to do.

kanyon · Silver Status Member

Jaxom....
If you are going to use a standard type PCP pump & not build a pump
Your system will be very long prob 300mm longer than the one in the vid
as your con rod will need to be longer than the pump stroke.
Don't use rod ends for con rod conections they were NEVER designed for it
They WILL fail in time.

If I was to build one I would use the piviting pump body design but
I would build a pump with a 100mm stroke X 12.7 bore and run it at a 100rpm or so. And power it with something like this or maybe this!

Jaxom · Senior Member

Everything will fail eventually. I've seen rod ends like these being used before and they still work perfectly fine years later. The key, like any bearing assembly is making sure they're lubircated when needed.

I thought about the stroke length and such, I don't see anything wrong with "short stroking" it. True, the most efficent way to go would be to have the plunger go all the way to the top on the up half of the stroke, and then all the way back down to the bottom to complete the stroke. But as you say, that'd make the entire thing overly tall. But what if the end of the top stroke was half way up the pump assembly? Who cares how many strokes it now takes to fill a tank, the motor is doing the work for you.

Speed/motor issues. I mentioned using a motor that that's capible of 65rpm. I think even that might be too fast! Think for one moment how these pumps were deigned. They're a manual pump you're attempting to motorize.

So let's say we find a physically fit, never smoked anything, muscular 19yr old male. How many strokes per minute do you think he would be able to do on one of these pumps? Speed this all up to far, and you could break or ruin the pump because you built up too much friction by going to fast.

kanyon · Silver Status Member

dummyracer36 · Senior Member

BBgunbob..... arent YOU the one that started this thread??? in a FORUM... to be DISCUSSED!!!!!!!!! then telling us to "shut the f**k up" ????
if the guy is a buddy of yours, and its gonna hurt your feelings to have his designs "nit-picked" then maybe you shouldnt pimp his product in a place that freely discusses designs and principles.

rsterne · Moderator

A lot of the comments made could be taken by the designer and including in improving his design.... Some of us actually have significant mechanical design abilities.... Rolling Eyes

Bob

kanyon · Silver Status Member

Very simular to the guys on 54..
seems to be water cooled....the rocking motion of the pump
seems to oparate a water pump.....

Jaxom · Senior Member

Kanyon,

I'm willing to listen to advice. Since I'm very much interested in this project. After what you said, I've been giving this even more thought.

The first time this pump was discussed was in the General forum. I casually mentioned that "we" could design something even better. I even went so far as suggest we could build a pump assembly that was more compact. Although, as someone pointed out I was incorrect in thinking we could have a pump cylinder of any diameter. This, as the other person would require a much larger motor to be used. His suggestion was to use a smaller diameter pump cylinder.

For a smaller compact pump, the first revision I'd make would be using a smaller motor that has a 90 degree geared turn. This will make it more compact and keep the center of gravity more stable. Then instead of a belt I'd use a sprocket and chain arrangment from the motor to a second sprocket. This would just move a rod that's run through a pillow bearing.

On the other side of the pillow bearing, that's where you then mount the disk with the offset pin or bolt to which you connect the first sphearical rod end..to connecting rod, to pump shaft.

Kanyon, since you have more experince at these things I'ld like to hear what you would think would make a good pump assembly. I'm thinking along the lines of say 1" i.d. stainless that's 12" long. You mentioned porting, I'd make it side or bottom (side) ported. That way you're filling the pump with fresh air on the up stroke. I'd also make sure there was a quality filter on that port as well.

Your thoughts?