Home made peristaltic pumps - Page 4

Yorg · 06-14-2009, 09:41 AM

One of the limiting factors in getting a HERMS system to ramp quickly is the rate of flow.
Assuming grain bed compaction doesn't replace the flow rate as the limiter, this peristaltic pump could be a great solution to quick ramps using HERMS and RIMS.
In my system, my March manages about 8 litres / 2 US Gall per minute.
I would like 3-4 gpm. from a peristaltic pump to make it a significant change from the March for the above purpose.
The priming advantages aside of course.
So Silverbrewer have you arrived at any design specs we can pass to the CAD guys?
Don't mean to rush you....

Cheers.

silverbrewer · 06-14-2009, 09:21 PM

Yorg....the mk1 has 1/2" pipe on a wall that is 160 mm radius. The construction leaves a bit to be desired, but once primed it will run between 0.55 litres pm (0.5 us pint) at 8 rpm to the max I have run it at so far that was of the order of 120 rpm and 4 usgpm. I have just had it pump vertically up a 15 ft length of 1/2" stainless tube with no problems at 105 rpm, so that is quite a big flow range.

My main concerns at the moment are how it will perform when asked to pump hot liquids, (as that is what it is going to be dealing with, even though it can be placed after the cooler during boiler to fermenter operations, it will still see mash temps in my rims) and how the tube will stand up to the rollers giving it a constant hammering....

I cannot really test the tube longevity in the mk1 setup, as the MDF crap it is made from gives off a lot of wood and glue dust that settles on the outside of the pipe, so it would not be a fair test until it is made from something nicer like nylon and is constructed in such a way as the tube and walls etc are sealed from outside contaminants.

That said, I have it set up to run at a constant 46 rpm, (that will give 4.6 litres per min.) and over the next week I will be running it all the time I am at home, to give it the nearest I can to a continuous test. So far it has run for a couple of hours at that speed setting.

When I get a free weekend, I will set up a similar test, but at high temperatures.

The Mk 2 is taking shape, and might be a single wheel, running in a 3" length of 1/4" wall thickness alloy tube of about half the size of the Mk 1. I saw a whole bunch of alloy tube remnants when I went and bought a length of stainless 1/2" tube last Friday, so I will be buying a bit of something suitable as soon as I can. I have bought three conveyor wheels from RS, item no 2352224 ...... that has good solid ball races and is 2" wide, 1 7/8" dia and runs on a 15 mm shaft. http://uk.rs-online.com/web/search/searchBrowseAction.html?method=searchProducts&sear chTerm=2352224&x=15&y=8

Having my lathe run the pump is a brilliant idea.....I have fitted a potentiometer into the lathes existing drive electronics that gives zero to max revs in whatever gear setting I put the lathe in. From outside the shed, on a brewing day, the potentiometer is a pump control knob, and from inside it gives the lathe infinite speed control when used as a boring old lathe (Pun intended)

I have taken pictures and a video, and will post them when I get a bit of time and also work out how it is done!!

Yorg · 06-16-2009, 12:42 PM

I get the impression that running mk1 at something like 100rpm wasn't giving you the impression that this would be a normal running speed. Would that be because of the MDF construction, or inherent in the design?.
Is mk2 an improvement for same purpose as mk1 or is this version for something else altogether - I think you had mentioned something about a spererate pump for sparging?

Since I don't, and i suspect most others don't have a lathe hanging about, what power/torque specification would a motor have to be? I thinnk you mentioned something about a wiper motor - are you thinking it would do the job.
Would a wiper motor be speed controllable via pulse width modulation do you think?
Cheers.

sjlammer · 06-16-2009, 05:27 PM

How about picking taking a piece of 6" schedule 80 pvc pipe and cutting off a 1" slice of it. then you could sandwich that between two pieces of mdf, steel, etc. I can't figure out how to make the roller assembly without access to a machine shop.

silverbrewer · 06-16-2009, 07:53 PM

These pumps may well work fine at 100 RPM, or even faster? Now that I have shown that they may have the capability, it needs someone to make a proper one, then use it for a year or so before we can be absolutely sure. (I am going as fast as I can) The same goes for the sizes of motor required. Using wiper motors would enable everyone to have a cheap power source, but that may be wishful thinking. Reducing the speed of an electric motor electrically reduces it's torque proportionally (I think) so it is much better to get the speed down to whatever you need using reduction gearing of some sort, be it chains, belts or gears. The good news is that if you reduce the speed of a motor mechanically you INCREASE the torque proportionately! If the dérailleur gear sets from push bikes can be made to work back wards, that would do it and give you a selection of gears to choose from! Some sort of simple chain tensioner should keep the chain from falling off.....Pulse width modulation would do it as well (but with the reduced torque problem), so get a sizable scrap motor from somewhere and then gear it down, then speed control it for fine adjustment. It most likely won't be pretty, but pretty costs $1800! so settle for ugly.

As soon as I get my 15 mm drive shaft coupling from RS I will connect my Mk1 pump to my large motor rather than my lathe. (this motor is in the pics and is about 4 times bigger than a wiper motor, it is geared down to 120 rpm mechanically and also has electronic speed control on the 240 volts) If this works, I will then try it on a 12 volt wiper motor and see how that manages. My guess is it will get very hot, but who knows. In the meantime, I am endurance testing the MK1 at 40 rpm on the lathe. It has done 8 hours so far. (2X4hrs)

The Mk 2 is being made mostly because of the crap MDF construction of the Mk1 and the fact that the skateboard wheels I used need to be a tad wider to fully squeeze the tube completely, this lack of squeeze at the very edges is causing air to pass the rollers slightly and so it needs a few revs before it primes. Fully squeezed, it will prime at any speed.
Sjlammer...please note that the 1/2" tube needs rollers of at least 27 mm wide, so a bit over 1"

I don't see the need for such a high flow rate as 4 USG PM, but feel free to enlighten me if I am wrong...I was going to make two pumps using 1/2" silicone tube and a bit smaller wall radius, say 100 mm, using 1/4" thick walled aluminum tube, or some of the large plastic tubes used for water mains under the street! Each pump will be made wide enough to let the 1/2" tube overlap, so it then only needs a single wheel, but that wheel needs to be at least 60 mm wide. So that will probably be two bits of pipe about 6" long. Each bit of pipe will have to have an arm to hold the wheel and two solid end plates to hold the bearings and seal out any dirt, unlike my Mk1

The plan would then be to use one pump to put hot liquor into the mash tun, say 60 rpm to get about 6 litres per min) one pump to circulate the mash liquor during RIMS, say 20 rpm to get about 2 litres per min, both pumps to sparge, at say 5 rpm to get 0.5 litres per min. Then either one or both pumps to circulate the boiled wort through the plate cooler and then back to the boiler to swirl the cold break at 60 rpm and 6 or 12 litres per min, and then the same to transfer the cold wort to the fermenter.

My biggest fear is that the pumps have the ability to suck at a stuck mash until it solidifies into concrete, so hopefully the rims process will settle the mash out to a nice filter! March pumps will just sit there waiting for liquid in the same situation....anyone wish to comment?

Do the flow rates above make sense? If you want higher flows to get HERMS fired up fast then just use two or three pumps on the same shaft, or two or three tubes in the same pump...just make everything wider and use a strong motor!

silverbrewer · 06-18-2009, 02:11 PM

Fantastic news guys....The Mk 1 pump turns just fine with a windshield wiper motor.

The thing is out of a Range Rover Discovery, and has two speed settings which under no load give 60 and 40 RPM. driving the pump on the faster setting the pump slows down to 37 RPM and pumps 3.55 litres per min, which is 0.937 US Gallons.

The motor is going to get mighty hot, but hey, you've just got to make a small water jacket for the motor case and either cool it with tap water or knock up another tiny peristaltic pump to flow some water through it !!!! I will run it until my leisure battery gets low, or the motor melts, whichever happens first.

Houston, we have cheap pumps......

jcdillin · 06-18-2009, 02:17 PM

Woohoo, thats great news!

jcdillin · 06-18-2009, 02:32 PM

I'm currently working on drawing up a model in solidworks, after it's done I can export it to other formats for whatever cad software people may have.

Soon as I have it finished and find some material I am going to cut one out on the cnc and see how it works.

silverbrewer · 06-18-2009, 03:27 PM

Yea I'm dead chuffed with it! I have had the wiper motor running for a hour and it does indeed get hot! Smokin would be a better term to use, so anyone going down this route had better (read must) source a wiper motor with a steel motor body rather than an aluminum one so a copper water jacket can easily be soft soldered on, and set to work.

To connect it to my 15 mm dia pump drive shaft, I made up a 2" length of 15 mm dia steel and drilled and tapped a thread concentrically in one end. This just screwed onto the motors output shaft until it hit the start of the splined cone that seems to be universal on these things. I then clamped the two 15 mm shafts together using a proper shaft coupling with decent clamping screws. Jubilee clips and a bit of old hose pipe will not stand the torque!

An hour long test at that temperature means that the motor is basically up to the job and we just need to stop them dying by getting the temperature down to reasonable levels. From previous work, water cooling the motor bodies of electric motors "in distress" I can say that water cooling is mighty effective and would expect the motor to not get past luke warm if a water supply is rigged up.

Yeaaaaaaaaaaaa!

jcdillin · 06-18-2009, 03:33 PM

So are some photos of my pump design. Now these are based on Jonathans pump design in the other thread. I really liked the look of the pump and how compact it was.

This is designed for 1/2" tubing.

Here you can see the main case, you would just cut two of these out and then sandwich them together.

These are the covers, again you would cut out two of them. I'm planning on cutting them out of 1/4" acrylic

And here is the beginning of the assembly, I still need to design the rotor and figure out how to mount bearings.

If anyone wants a copy of the drawings please let me know, or I will be posting a download link once I have the rotor finished.