Home made peristaltic pumps

[silverbrewer]

It's been worrying me that during sparging, with two of these pumps working in unison, the mash could get sucked onto the false bottom, as these pumps won't "cry uncle" like the March pumps would.

It has just dawned on me that if a flow loop is provided so the flow can get back to where it came from if there is a restriction then the flow can be controlled with a couple of taps, or even a couple of clamps to just squeeze the silicone pipe!

 

[conpewter]

If there is too much suction going on the silicone tubing will just collapse.

 

[silverbrewer]

Doh! why didn't I think of that! )

 

[Yorg]

So what's the thinking on hose compression:
If I used jdcillin's design, I would still have to design the roller assembly ( it would be great to have a CAD of that to discuss) and I would have to decide the measurement that would result in the hose being compressed by the wheels. So would I compress the hose so that it just closes off and use that measurement as the width/thickness of the compressed hose, or would I give it a good press and use this smaller measurement as the thickness?

 

[silverbrewer]

Compress the hose just enough to give it an air tight seal. (check by blowing down it) Any more than that will only cause unnecessary strain on the entire assembly. I think I got my gap right, but my wheels were about a 1/16" too thin so there is a slight air leak and I cannot do anything about that until MK 2 The air leak past the wheels causes a reluctance to prime in air unless the revs are increased. Once it is pumping water, everything is fine. If a single wheel system is employed then you only have one wheel to position correctly, so you could even include a bit of adjust ability in the system. Note that with a single wheel, the tube must overlap itself before it leaves the circular wall and the wheel width must be twice as wide to accommodate two squeezed tube widths.

 

[beerthirty]

Peristaltic pumps are notorious power consumers. If the wiper motor is getting that hot a cooling jacket will have little effect. It is the windings that are producing the heat and they are insulated with lacquer as they are wound. This thin layer will burn off under high heat causing the motor to short. Cooling the case will do little to reduce the winding temp.
SB, try wrapping the rollers with a couple layers of duct tape to increase the diameter and create a positive seal. I know its ghetto but they don't call it 100MPH tape for nothing, its tough stuff.
Many peristaltics use spring loaded rollers to account for minor machining and assembly descrepencies and reduce the chance of blowing tubes from over collapse or pressure spikes while still keeping a positive seal.

 

[Yorg]

Those seem to be sound observations and suggestion Beerthirty.
Any suggestions/ scanned hand sketches on a design for spring mounted rollers - one for a CAD talented brewer to draw up for the rest of us to critique?
(Open source peristalitic pump design )

 

[beerthirty]

To prevent the roller from cocking to one side from uneven pressure, the roller would need to be mounted to a carriage that would slide on the rotor arm. The spring could be placed inside the carriage against the end of the rotor arm.

 

[silverbrewer]

When designing the Mk 1 pump I did indeed consider making the radius that the wheel was set at adjustable. The initial thought was to make the adjuster so wheels clamped tight in various positions, like the adjustable chain tension on an MX bike..... but then having it spring loaded crossed my mind. I was thinking along the lines of a trailing arm pivoted where my wheel is now and about two inches long. The wheel is then at the end of this arm and an adjustable link, or a spring loaded link goes across to the main arm from the wheel end of the trailing link. I ruled out these options as un-necessarily complicated, and un-needed provided the pump was made accurately. The air problem with my pump is because the wheels are not wide enough. It is not diameter, concentricity or gap related.

My Mk 2 pump is going to be made out of 1/4" (or thicker) walled alloy tube. Two alloy, or clear acrylic end plates are going to be turned up to fit perfectly into each end of a 4 inch (or longer) length of this tube and give support for two sturdy sealed ball races with a ID to suit my 15 mm drive shaft. This way concentricity should be held within a few thousandths of an inch, and the tube will be in a sealed cavity, so it can be lubricated with something, perhaps food grade white grease? I will have only 1 wheel to reduce wear on the tube.

I fully agree that using a windscreen wiper motor to run this pump is pushing your luck. As soon as a properly engineered Mk 2 pump is in existance, I will run the thing with a watercooled wiper motor 24/7 just to see what reliability we can expect from such a cheaply avaliable motor. Mine ran fine on a small 4amp battery charger

With all these things sorted, it could still go pear shaped once we try to pump hot liquids for any length of time, but I am crossing my fingers and hoping that empirical testing proves all our worries are un-founded

 

[jcdillin]

I've been trying to draw up a design for different spring loaded versions and from what i've been doing I think it makes it all a bit complicated.

Wouldn't it better just to have different sized rollers that you could put onto the shafts that way you could make adjustments just by changing the size of the roller.

 

[beerthirty]

Here is an idea you may want to play with. wheel carriage made like a caster(trailing axle) and instead of a single post use 2 hollow tubes that would slide over posts on the end of the rotor arm and install the springs in the tubes to act against the end of the posts. As long as the clearance between the post and tube was minimal it should slide easily without binding. If going with a multi roller where the tubing doesn't overlap, guides could go straight off the arm to help keep the tubing aligned just before the trailing caster so multiple tubes could be laid in the same housing and run by the same roller.

 

[jcdillin]

Interesting thought, I am going to give that some thought.

Today I plan on cutting out the housing just to see how it comes out.

 

[silverbrewer]

Good luck, hope it comes out alright! A good supplier of small bearings in the US is boca bearings. Check out their website, the 99 cents page is exactly that ! Every bearing is 99 cents.

 

[Yorg]

By the way, how loud are these pumps, compared to a March?

 

[jcdillin]

I would think it wouldn't be much louder than whatever motor you were using to drive it.

 

[silverbrewer]

I have not heard a March pump, but it is revving fast so I would say a peristaltic would be much quieter.

JCD, I just saw your pump design. You should be able to fit the bearings into the side plates if you use thin bearings, or make the plates a bit thicker. You will need at least two rollers at 180 degrees separation as you have not overlapped the tube on a 360 degree wall ( IE 380 degrees of tube before the tube starts to leave). Three wheels (at 120 degrees) would be better to ensure it primes easily, as with two wheels you are bound to get a bit of back flow as one wheel arrives and the other leaves your 180 degree "wall". Looking good though, when will it be getting made? Did you see my link to wheels that already include two bearings? You must be able to find similar stuff over there....

I have just made a water jacket for my tiny windscreen wiper motor from a dog food tin!! I have tried it out and there are no leaks, so I will be endurance testing it soon. I am aware that the armature and windings will still be getting a hard time, but a lot of heat will be getting removed as the pump circulates water through the jacket and back to the large bucket. The motor was free, so I have no qualms about testing it until it fails! This test will just be for fun as I would say that these small geared motors are not really up to the job. If anyone is serious about going the peristaltic route they must source a decent size geared motor, or come up with a gear reduction system to suit an ordinary motor. Shop about, as there are hundreds of redundant motors getting thrown out all the time.....
My idea for getting home made gear reduction would be to knock up a couple of sturdy plates like the side walls found on a "monster mill" have three shafts set at suitable spacings to accommodate push bike pedal sprockets and rear gear sets. Arrange the drive of the motor to drive the smallest rear gear on shaft 1 with a chain to to a big front sprocket on shaft 2. Fit another small rear gear on shaft 2 and drive shaft 3 with a chain to another big front sprocket mounted on shaft 3 etc etc. chains can dangle down with a weight hung on one of the tiny sprockets from the dérailleur mechanism to get a chain tensioner If the sprockets can be clamped to line up with a selection of gears then various ratios will be possible. You just get whatever sprockets you want lined up, drop a chain onto them and off you go.....Then your large motor, which in my case is 150 rpm flat out, can be set to give virtually any lower speed and therefore any lower flow rate, without reducing the speed electrically, and loosing torque.

 

[jcdillin]

That was my plan, I am going to cut almost all the way through the plates and then press fit the bearings into place. I think they will probably last just fine.

Yeah on my rotor design i'm going with a 3 wheeled design just to keep it simple. How much clearance did you leave between the wheel and the wall?

I am waiting for material but I have programmed it up to cut out on the cnc and i'm tempted to do a version out of wood just to see how it works. But the final version will be made out of something better like derlin or nylon.

 

[beerthirty]

I would think the clearance would be twice the wall thickness of the chosen tubing minus a couple thousands. (this is where the spring loading comes in, different tubings and elasticity of the tubing.) Of course the elasticity would play a roll in the spring rate.

 

[BrewBeemer]

I would think the clearance would be twice the wall thickness of the chosen tubing minus a couple thousands. (this is where the spring loading comes in, different tubings and elasticity of the tubing.) Of course the elasticity would play a roll in the spring rate.

A couple thousands of an inch would be within the tubing wall differences of the tubing production runs besides different brands of tubing selected.
I was thinking .010" to .015" preload against the tubing as the two walls of the tubing will compress half that amount per wall thickness allowing for any wear thus preventing any future backflow leaking problems as time is put on this pump.

 

[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)

 

[Dadrick]

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]

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]

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]

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]

Any updates??

 

[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....

 

[BrewBeemer]

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]

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]

What is shim stock?
Any links?

 

[silverbrewer]

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"

 

[BrewBeemer]

Kind of like driving on the wrong side of the bloody road mate?
I was across the Pond during the "Storm of the Centry" in London
heading north on holiday for an additional two weeks, cut it short
and headed back to California. So sad no Matchless and Velo single
parts. Ya still shut your pubs at 11 PM? So used to 2 AM in the states.
No worries, shim stock is our standard wording state side, now the propeller
shafts a hoot as well a "hearty tug with a one foot Tommy Bar" for a torque
spec on a head bolt. The bonnet and boot plus anti-clockwise are fun to read
about. My wife was asked "what time do you want to be knocked up?" That we laughed for years onward. Driving in the states, horn standard equipment, blinkers optional use. Still 17% VAT? Not 17% ABV, now go get pissed chap.

 

[silverbrewer]

Here are the three arms of my Mk 2 peristaltic pump wheel spider

The component parts are here.

Here is the aluminium tube that the spider will be put in, It is 11,1/2" id 1/4" wall thickness. The inside of this tube will be the "outer" wall that the three 1/2" silicone tubes will be squeezed against by the three rollers.

 

[jcdillin]

Whoa, that's sweet!

 

[cyberbackpacker]

Wow, that thing is going to be HUGE!

 

[silverbrewer]

I've never had any complaints about "hugeness" before!!

Seriously though......It is going to end up 12" diameter and 6" long, but remember that it is THREE pumps combined.

It will/can sit high up in the brewery (shoulder height), as it can prime itself.

It will be mounted on a wall, with the drive coming from the other side of that wall, so a very neat setup. I intend setting up the keggles so that each one has a stainless 1/2" tube going down into it from the pump, so I will not need any holes in the side of the keggles at all, just a straight keg with the 12" hole cut out of the top. Temp probes, and all inlet or outlet tubes will come in from the top. Well, that's the plan anyway!

Now, will someone perleeeeese tell me the outside diameters of Blickmans punched false bottoms, so I can order one to go into my mash keggle.....

 

[Hang Glider]

Those are some incredible engineering skilz

 

[cyberbackpacker]

I intend setting up the keggles so that each one has a stainless 1/2" tube going down into it from the pump, so I will not need any holes in the side of the keggles at all, just a straight keg with the 12" hole cut out of the top. Temp probes, and all inlet or outlet tubes will come in from the top. Well, that's the plan anyway!

I have a peristaltic pump with 4 heads that I plan on utilizing in the same way. Draw from the bottom up without a need for excess holes, or even a ball valve in my case.


Good luck.



...

 

[Catt22]

Now, will someone perleeeeese tell me the outside diameters of Blichmans punched false bottoms, so I can order one to go into my mash keggle.....

The Blickman false bottoms are designed specifically for use with their kettles. The Blichman kettles have a stepped side near the bottom that supports the FB. You could probably modify the Blichman FB to work with other kettles by adding some feet to it or figure out some other way to support it.

 

[Yorg]

You are a friggin legend.
Once built and tested, can you post some CAD drawings and some part specs and sources?

 

[bendavanza]

That thing is going to be a beauty. Super clean looking parts!