The parts for this Mk 2 pump are so far pretty much hand made. All of this could be done if you enrolled in an evening course at the local engineering college, which shouldn't cost much. The Mk 2 pump build will indeed need some access to engineering equipment, but down the line, once this Mk 2 pump has been well and truly tested, there is no reason why a Mk 3 pump cannot be designed that uses only simple readily to hand parts.... so that anyone can make one, with a tad of ingenuity and a simple toolkit!
I was being shown a brand new brake drum the other day that would have been a good starting point, but the bloke at work was only showing it to me because he had recently put a .22 bullet through it with his rifle! While he was chuffed that it had gone right through one side and dented the other, I was looking at it and thinking "****, I could have used that you berk"....My point here is that brand new brake drums cost very little and give a perfectly machined circular surface.
On my Mk 2, all the shafts are silver steel, which is already ground to exacting tolerances, so it fits the bearings exactly with no work required except cutting them to length. (Note here that metric silver steel is machined to a plus nothing, minus a couple of thousanths, while imperial sizes might be a plus or minus tollerance, so bearings may not fit and you will have to go with metric) I was lucky with the steel tube for the rollers....that is also ground, so cleaning it up to get a good surface took a few minutes with 800 grit paper.
The arms on my Mk 2 are cut out of a very hard foam that our 5 axis guys use to carve car models out of....... but they could just as easy be made from wood. The shapes were drawn by hand and cut on a simple band-saw. The round hole cut in the middle of each part is so I could hold each part down on the top slide of my lathe, using the tool post bolt. I then drilled one of the shaft holes with a 15 mm drill stuck into the lathe head. I then indexed the cross slide the appropriate amount and drilled the other shaft hole. that way, the shaft holes were all drilled exactly the right distance apart, and they were parallel, and not skewed either. Fine slots were cut in the bases of each leg and holes drilled for the clamping screws.
The end plates for the big tube will have to be made on a BIG lathe, so that could be a stumbling block for this design to be made by one and all, so those without access to a machine shop will have to wait until Mk 3
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Blessed are the "cracked", for it is they who let in the light.
Last edited by silverbrewer; 07-25-2009 at 05:40 PM.
A lathe of 16" is available, made by the Pratt & Whitney radial engine manufacture. My Atlas is only a 12" swing. For drums look into big rig
18 wheelers as they have an ID of 16 1/2" by 7 3/8" deep shoe depth.
One problem your dealing with app 55 pounds of steel. I have used them as grinder and buffer stand bases. Big rig drivers as friends with worn out drums
available. F250 Ford pick ups of the 67 thru 76 era have 12" x 3" drums ortherwise look into F350 truck drums as they are wider. Cast in steel with finned aluminum drums on my 56 300C Mercedes drums are app 4 1/2" wide at the shoes.
Anything is better than having a collection of March pumps with what they are
the asking for them, this just rubs me wrong. I sold my last brewery with two March pumps with their priming PITA plus their high cost even used. I will explore the use of other pumps.
One last thing... you need to make sure the tubing can be replaced in a matter of minutes. I have peristaltic pump using high-temp silicone tubing that occasionally bursts during use. I think a the regular use of hit liquids and cleaning fluids causes the silicone to become brittle. Luckily - I have never had the tubing split while pumping my beer or mash.
Just to update on progress, I have now fitted bearings in each end of the three rollers and they are all fitted to the "spider".
The 12" aluminum tube and 10 mm thick Perspex end plates are all at my mates house waiting to be machined on his big lathe. The trouble is, he is in bloody Mexico!!! The only good thing about that is he is bringing me back a couple of propane gas rings, and one of "Derrins" stir plates.
JVD-X :- To combat emergency down time I have three tubes in the single pump body, so if a tube fails I can switch to the spare to get out of trouble, plus if needs be, I always have my MK1 model close to hand, even if it is only made of wood!! Although this is a "how long is a bit of string" type question, how often do you reckon the tubes will need replacing?
Regarding popularizing this type of pump, I think that would be a great idea. I still think making one based on a readily available brake drum is a good starting point, to keep the engineering simple. The trouble there is that what is a popular drum Stateside is not available here, so one of you lot needs to join in and do some development. I think that once the design has been finalized they should be really cheap to make, so the plan would be for everyone to have two or three of them driven off a single shaft.
To start the ball rolling, I see some kind of cheap standard brake drum cut away so only half of the drums surface is intact forming a semi-circle, but cut so the centrally machined circle where the drive shaft enters is still intact.
The ends of the drum surface are carefully rounded so as to not damage the tube.
Next, a bearing holder is manufactured that holds a couple of ball races, and that assembly sits tightly within the drums shaft entry hole so as to pick up on the concentricity that has already been provided for us. A suitable shaft is placed through this bearing holder and a two roller arm is fitted within what is left of the drums swept surface, to crush the tube.
As mentioned before, over here, metric sized ground shafts have a negative tolerance, so they fit very exactly, (but with a clearance) into metric bearings, but I think imperial ground stock has a plus or minus tolerance, so a good fit cannot be guaranteed. Do you guys work in metric? I work in metric all the time, but I still think in thousandths of an inch as soon as small stuff is encountered, but that's just cos I'm an old git.
The sort of motor that is used for grain mills should be able to be utilized if one is available, or the sort of geared motor commonly found driving industrial roller shutter doors will be well up to the task.....
Having said all this, trying to cover all bases is a big task as everyone has different abilities and equipment. A DIY build of this complexity should be aimed at peeps who either have suitable equipment, or can enroll in a model engineering class at a local college..where there are always people ready and willing to help....I suppose there is always the option to bulk buy in the manufactured bits from a small engineering company! This is after all a very well attended forum!
Discuss!!!!!!!!!
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Blessed are the "cracked", for it is they who let in the light.
Last edited by silverbrewer; 08-11-2009 at 08:02 PM.
Wow, quite an update! I think the idea of using a brake drum would be good. I have no expertise on the engineering that would be required but I would very much like to get my hands on the finished product. Most of the peristaltic pumps I find are either very precise and small or absolutely huge. Seems like there is a big market for a general purpose P-pump like this.
Using a complete front drum with hub assembly including the tapered bearings then all you would need is a machined center axle that fits the two different cone bearing bores for a concentric mounting point for your roller spider to mount onto. Threaded axle with jam nuts for slight bearing preload. With the drum mounted on a bracket off the hub lug studs it would then be easy if you have the axle extended past the outboard side of the hub for a connecting means to a 90 VDC gearmotor with speed control. For holding the tubing in their channels or pockets machine oversize aluminum rings with the proper spacers, freeze the rings or use dry ice then install the rings. Once expanded into the drum remove the spacers between the aluminum rings these channels for your tubes to set in. Like you mentioned before, cut away what's needed to pass the tubing in and out of the drum which can just be holes in the channels angles into the direction of the tubing and radiused to prevent any tube chafing. building the pump body this way 90% of it is from a automotive breaker just pick the diameter drum you want, make the spider to your drum and rollers as well the aluminum rings. Surely those tapered greased wheel bearings will outlast a lifetime of use going from 1,000 pounds plus loading to almost zero bearing loading just rotating. This is how I would build one as there are many drums available at 12" ID and smaller, my lathe can only swing 12" for the aluminum tubing support rings. I would build it to allow for grease seals at both ends of the hub.
Stateside there has to be a ton of cheap drums for chevy trucks. Measurements are done in either metric or inches, depending on who's doing the work.
You got that right after going thru 3 chebbie trucks until I got smart and changed brands. Dodge still a no. Went Blue Oval sold the last truck at 922K miles it passed 1,032,000 two years ago second owner now.
Those miles with the Blue Oval since 1972 with a 69, never looked back. A mint 68 F250 Camper Special with 69K original miles I had to have but the 390 had to go the 520 FE filled my needs.
JVD-X :- To combat emergency down time I have three tubes in the single pump body, so if a tube fails I can switch to the spare to get out of trouble, plus if needs be, I always have my MK1 model close to hand, even if it is only made of wood!! Although this is a "how long is a bit of string" type question, how often do you reckon the tubes will need replacing?
I have found that I get about 10 batches out of tubing. The tubing is not cheap but the length is really short, so it doesn't cost much. In addition, I use the pump for cleaning and sanitizing as well. For example, I use it to pump PBW and Starsan through my counterflow chiller; I also use it for my RIMS. This means it is easily running 2-4 hours each brew session.
So - as a guesstimate I would say you would need to replace the tubing every 30 hours of use. The point being, you can't really be sure when it's going to split - I have been lucky. Also - I have started taking the tube off the rollers between batches to minimize the strain on the tubing. I don't know if this will make a difference but I haven't gotten to my 30 hours since starting this practice.
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