Home made peristaltic pumps - Page 7

Dadrick · 06-25-2009, 10:54 AM

Quote:

Originally Posted by silverbrewer

Remember that from day 1 if needs be, or after a bit of wear has set in, more squeeze can easily be had by fitting a bit of flexible shim stock behind the tube, for the entire width and length of the wall.

I've been quietly following this thread. To me this seems like the best KISS solution possible. The ability to fine tune the wheel pressure without going to some extreme engineering solution with springs or tensioning screw adjustments. When it comes time to replace the tube remove the shims and start over.

**BrewBeemer** · 06-26-2009, 05:12 AM

Quote:

Originally Posted by silverbrewer

For my 2 cents worth, I think .010" to .015" extra compression is a bit too much. I think that as soon as the wheel squeezes the tube enough to prime at near zero revs (IE by hand) and stay primed if you stop rotating it, then that is enough. Any more pressure will just make the pump harder to turn.

Remember that from day 1 if needs be, or after a bit of wear has set in, more squeeze can easily be had by fitting a bit of flexible shim stock behind the tube, for the entire width and length of the wall. In fact, any adjustment required can be done this way, as long as the wheel is made wide enough in the first place, unlike mine, which was limited from the outset by a bad wheel purchase (£10 skateboard)

The .010" to .015" of compression on the tubing compressing thru two wall thicknesses of the tubing so the tubing wall thickness as a wild example of
.090" is rather thin compressing the material .005" to .0075" on .090" of a soft flexible material at a very little amount of compression. Sorry I don't buy your reply, again it is a forum and all replies are your right so I will respect yours.

silverbrewer · 06-26-2009, 04:37 PM

Hi Brewbeemer...I didn't mean to offend or critisize. As you say ,we are all on the same side here , and we are all guessing to some extent, although from your interesting and constructive comments it does seem you have experience of these pumps, or silicone tube. I was just trying to say that I think that "a seal" may be obtained with a bit less pressure.

Today I bought a 5 1/2" length of 12" od 1/4" wall thickness aluminium tube for £10. With a bit of luck I may be able to cram 4 bits of 1/2" tube in there to get 4 pumps.

This should give me the ability to use all 4 pumps at once to give a high flow rate without a high RPM, or, in the event of a catastropy, there is going to be other useable pumps to rescue the situation if this silicone tube proves to be un-reliable, which I doubt.

Looking at the tube on the dining room table, it looks massive for a bit of alloy tube!

silverbrewer · 06-27-2009, 09:43 PM

Here are photos of the Mk1 pump taken apart. There are two thin plastic layers that are not in the exploded pics. They are there to get the width of the central layer to the correct width. I needed 27 mm wide and the MDF sheet was only 25 mm wide. The skateboard wheels run on standard skate bearings and the wheel carrying spider has two Oilite plain bearings in its centre. They were put there so the pin that picks up drive from the shaft could be removed so the pump would be disabled but the shaft could still be driven while in the stationary spider.

Yorg · 07-15-2009, 07:21 AM

Any updates??

silverbrewer · 07-18-2009, 10:57 AM

I am getting on with the Mk 2 pump, but have been a bit tied up with other brewery related tasks...

To get ready for the brewery build (Shed extension), I have chopped down two of next doors large trees, dismantled and re-assembled a small shed to elsewhere in the garden, dug up and re-positioned one of those bloody heavy 8' tall concrete fence posts and had a general tidy up. The extention will give me a 10' x 23' covered area, with a 16' x 5' covered corridor along the back. Got to go buy the wood soon.....

Anyway, back to pumps.

I have trimmed the ends of the alloy tube (12"od 11 3/4" id 5 1/2" long)
I have two bits of 10 mm thick 12" square Perspex that I have to turn a 11 3/4" diameter shoulder onto and bore holes for bearings. These will sit into the tube ends and provide concentric bearings for the shaft.
I have sorted out how to machine the three arms for the rollers, but cannot finalize the dimensions until I make the rollers.
I have got the steel tube for the rollers and am now searching for some round alloy stock to make the six end caps/bearing holders that will go in each end of each roller and hold concentric bearings for the rollers.

To machine the larger stuff I need to visit my mate who lives 100 miles away! but I will get to do that soon I hope.

This pump will have three separate 1/2" silicone tubes, getting squeezed by rollers that are about 4" long and 2" diameter. This will give me the 2 pumps I need for sparging operations and an instantly available spare for emergencies. With all three tubes in use for high flow needs, I do not expect this pump to need to be turning at much over 50 to 75 RPM during use....

**BrewBeemer** · 07-18-2009, 02:00 PM

Quote:

Originally Posted by silverbrewer

I am getting on with the Mk 2 pump, but have been a bit tied up with other brewery related tasks...

To get ready for the brewery build (Shed extension), I have chopped down two of next doors large trees, dismantled and re-assembled a small shed to elsewhere in the garden, dug up and re-positioned one of those bloody heavy 8' tall concrete fence posts and had a general tidy up. The extention will give me a 10' x 23' covered area, with a 16' x 5' covered corridor along the back. Got to go buy the wood soon.....

Anyway, back to pumps.

I have trimmed the ends of the alloy tube (12"od 11 3/4" id 5 1/2" long)
I have two bits of 10 mm thick 12" square Perspex that I have to turn a 11 3/4" diameter shoulder onto and bore holes for bearings. These will sit into the tube ends and provide concentric bearings for the shaft.
I have sorted out how to machine the three arms for the rollers, but cannot finalize the dimensions until I make the rollers.
I have got the steel tube for the rollers and am now searching for some round alloy stock to make the six end caps/bearing holders that will go in each end of each roller and hold concentric bearings for the rollers.

To machine the larger stuff I need to visit my mate who lives 100 miles away! but I will get to do that soon I hope.

This pump will have three separate 1/2" silicone tubes, getting squeezed by rollers that are about 4" long and 2" diameter. This will give me the 2 pumps I need for sparging operations and an instantly available spare for emergencies. With all three tubes in use for high flow needs, I do not expect this pump to need to be turning at much over 50 to 75 RPM during use....

All I can add is your on the mark with your pump building and drive until you'll get the results your after in due time.
I believe with the tubing diameters plus the low rpm's your at a "have a winner" coming together. Hats off mate. I'm going off pumps my machine shop was designing back in late 1969 thru early 73 when I finished my college and started working for the airlines as I had my FAA licenses by then. I must ask on your tubing what is the wall thickness and how much crush less than the two wall thickness are you at now in this last pumps design? This has sparked my intrest beyond spending any money purchasing any March pumps with all their priming problems plus the perfect sparge with two pumps working as one. I'm just adding what I never forgot when I was younger as these pumps were built in a prototype one off type machine shop I worked in while in college classes on swing shift. My dad helped this shop owner he made a short loan to him as dad purchased two new Bridgeport mills with optics at 0.0001" table scale readings for him. This was in 1969 I recall.
We also did production runs and machined cast aluminum electrocardiograph
machine bases as well pneumatic hand probe air blast units used to test
for the eye pressure glaucoma disease. My aviation job took me away from the machine shop but have a old Bridgeport and lathe in the shop at home.

On the pumps they had a stainless tube stub tig welded to a threaded nut, a bulb before the end of the stainless tube prevented the tubing in the pump from being pulled off as there was a collar to prevent the tubing from creeping off the stainless stub bulb from the nylon roll pulling inside the pump. Mind you this was 38 years ago. With your unit a 90 VDC motor like they use on those jogging tread mills will have the rpm's your looking for if a poly "V" belt reduction were used as well they should have a trigger wheel and LED to maintain a constant speed control under different motor loads. I just picked up a "KEYS" manufacture jogging unit due to the owner drilling into the side frame and ripping apart 12 wires of 26 gauge hence it a curb side rubbish unit. I stripped it apart, rewired the controller and motor which is 1 1/2 hp 12.7 amp @100 VDC motor. App 115 to 4,460 rpm's constant speed control under different motor loads due to that LED trigger assembly. I was also thinking this a perfect grain mill motor after a poly "V" belt reduction then a direct drive to a the grain mill without large pulley bushing side loading.
Keep posting your progress as i'll be watching. Take care. Carl.....

silverbrewer · 07-19-2009, 01:48 PM

Today, just for the hell of it, I set up the Mk1 pump and circulated boiling water for a couple of hours, at about what I am guessing will be the flow rate RIMS requires.. about 45 RPM and 2.5 USPintsPM. The silicone tube seemed to take it in it's stride, so there is another hurdle passed off the check list of potential problems! The test stopped when it started raining all over my electrics!!

Carl:- The tubes ID is 12.7 mm and the wall thickness is 3.2 mm. I am setting the pump clearance to 6.4 mm. If I find I need more "crush" than that, I will fit shim stock inside my alloy tube, behind the silicone tube....That way I can set the crush to whatever I like, and the surface finish on the shim stock will probably be better than the surface finish of my alloy tube, so the silicone will be happier.

I have yet to decide whether to lubricate the tubes within the pump case with anything? The pump case will be not quite "water tight" but should be Grease tight, so I was thinking "silicone grease" may be a good starting point? Perhaps I can get PTFE shim stock and then not need any lubrication...

Any "sensible" advice out there on lubrication !?

Yorg · 07-20-2009, 07:03 AM

What is shim stock?
Any links?

silverbrewer · 07-20-2009, 04:04 PM

Hi Yorg,

"Shim stock" is standard thickness sheet material available from stock, for making up thin spacers. (shim) It is readily available and does not need to be manufactured. It comes in a multitude of thicknesses from sheet metal suppliers, and can be steel, brass, copper, whatever.

There are weird differences in what we call engineering things each side of the pond...over here, the swirly cuttings that come off a metal lathe are called "swarf" and high carbon steel ground bar in 13" lengths is called "silver steel"