Tow Mixers

Has this subject been covered yet?
- Not a cement mixer you happen to tow to a site, but the kind you make out of a Rear-end differential and a stock tank ??

nope

and if you have links to good diagrams that would make me happy

About diagrams, schematics, etc. If I have some from the net, etc. I don;t mind sharing them, but I am extremely hesitant to start sharing details and particulars of my own designs on anything.
Whether anyone would think so or not, my designs have real value, and although I would not presume to try to sell or market them here, I do like to keep my secrets either for my own fondness of being two steps ahead of the world, or for eventual commercial use myself.
- I will see what I have in images to share though...

Here are a couple quick pics to show the way its done...
The trick is that you tow slowly, as otherwise, if yu were to actually drive down the road to a location with it mixing concrete, it would likely turn too fast, and either you would have concrete flying out all over the pace, or you could burn up the differential, strip its gears, or break something.

With one of these, if my calculations are right, you can make/pour over 21 cu. feet / 7 Cu Yards / 158 gallons of concrete, mortar, or other slushy material.
I have considered the idea of gathering grass clippings, manure, sawdust, etc. and water to make a fast compost slurry. - But again, would not necessarily be able to drive at normal speeds.

I have been trying (not too much time spent thinking about it yet) to think of some type of "Blade" that could be used at higher speeds, like a radical curve or something that could both slip through the mix without undue torque or flaying it around, and still adequately mix the contents.

interesting I'd definitely say it need to tow slowly and from the look of the pic of it assembled that unit has leaked a bit at the penetration for the mixer. I think it might be more effective to build a rocking mechanism and use one of the oblong tanks.

Can you post a link to where you found the pics please?

Links - I have hundreds, if not thousands of pics in my little digital library, so that's just not possible.
Pics are added to the net almost every day, so the best thing, and what I tell everyone on any subject is just to plug the right words into a Google image search. A rich source of ideas.

I'm sure that the point where the differential enters the tank could be dealt with somehow.
One possibility is from where someone made a tow mixer with a 55 gallon drum and used a tire rim as a spacer and support - which, with a stock tank or similar would make the area around that point much more rigid and help with whatever method of sealing it one could figure out. Personally, I would try to find some way to use a large thick piece of rubber or similar, carved just right to mate with the top of the differential and once the differential was sandblasted to bare metal, glued with a good contact cement, and screwed from inside the stock tank.

What I would like to figure out, or get ideas on, is how to make some kind of blade or stirring mechanism that could work at normal driving/towing speed. The only thing I can think of coming even close is a seriously curved blade/etc. and maybe getting some differential that has a lower gear ratio than usual - but even the best possible/available gear ratio would likely make little or no difference.

do you want it to mix @ 55 and low speed or just at low speed, also would simply building in a way to disengage the blades for higher speeds give you what you want.

despite that availability of truck axles you may want to consider some type of geartrain that spins the mixer slower slower than the wheels rather than the 3-5 times faster you get from common differential

for myself I would stick to slow speed towing and mix onsite because with a couple tons of concrete slurry in there that thing is going to really drag hard on a truck. probably wasting more gas than you would if you just used a small gas motor to power the rig, and exposing exposing you to drive line failure

also for higway speeds you are going to need some suspension to keep from busting the axle and warping the tank, just picture the forces of a good sized bump at 65 on that thin steel tank.

sorry if it seems I am saying it wont work, I'm just trying to anticipate issues

Anticipating Murphy's law is a necessary and integral part of good design and planning.

You have a very good point about shock to the tank with heavy semi-liquid weight in it.
I would guess that there would be a "happy medium" of how much of something could be kept in the tank.

I would not worry about the axle itself, as it would normally be supporting a lot of weight, but without suspension, it could have an effect on the wheel bearings first, and possibly also the axle or other parts.
Using a smaller gas-powered something may be an alternative, although that would be a fairly specialized thing, and might require significant extra expense.
There is another possible method of constructing it with an intact suspension. I may have a pic for that

Other wise, I will need to haul heavy stuff, including cement to the site anyway, so I would like the possibility of hauling and mixing it simultaneously.
Also, I would like to be able to gather materials for composting and mix them as well as I bring them to the site.

I was anticipating the problem of choosing a faster or slower speed to also find a happy medium of max speed possible for roads (Avg. of about 45-55 mph), and even a very slow speed will work for mixing around on site.

I found the alternate method where it uses a separate differential for mixing - let me know if this inspires any further options...

http://www.livinginpaper.com/mixers.htm

In this, the guy simply remounted a drive shaft to the other differential, but then the question is - drive shaft from what/where?
- Oh, I get it... He's got a truck where either he has to re-mount the drive shaft every time he wants to move/drive it or use it to mix, or otherwise he's got a truck that goes nowhere does nothing except mix concrete with its engine and drive shaft I guess...

I wonder how crazy it would be to somehow seal up the bed of a pick-up and use the bed as-is to mix the concrete? - A bit of a stretch I think...

I rather like that big mixer design despite the incoviniene of having to swap the driveshaft onsite it gives a huge capacity a vehicle which can handle the weight and a huge range of speeds with a big enough motor for the job.

I think if you made a standard pick up frame trailer with intact suspension your could mount a hydraulic pump on the drive shaft flange of the differential then use a variable speed type hydraulic motor to run the mixing blades that would eliminate the penetration in the bottom of the tank provide a frame and suspension and provide variable speeds. think your local scrapyard might have a couple forklifts to take parts off?

@Brice:
Yes, right on all counts.
However, for my own purposes, it would mean a lot more money, work, time, etc.
I'm planning a fairly large construction that must be completed within a short time.
I could do a lot of that, but getting and properly rigging such a set-up (Hydrolic or other motor) would push it past the margin of my plans. Thanks for the input just the same, as it may help others who check this.

I've seen something like that on one of the papercrete sites. Maybe even plans. It's been a while though.

The tow mixer is made from a rear end differential of an old car or truck  found in a junk yard.  It is turned upside down and the part that is  normally attached to the drive shaft of the vehicle, is sticking up through a hole that has been drilled in a 4 foot stock tank.  A  lawn mower blade is then welded on to the drive shaft, and when towed behind a vehicle, the lawn mower blade turns and chops and mixes the paper/water/cement mix.  You're only going 5 miles an hour, for 5 minutes or so.  It may leak water slightly, but bondo is used to seal most areas.  It is a super fast process.  I can't see why someone would want to do this going down the highway at regular speeds.  It's not designed for that. 

I attended a class last weekend, and it worked very well.  We mixed enough papercrete in the tow mixer for 1 batch to make 18 blocks that were  1 x 2 feet in size.  I would estimate that when set up, they weighed about 6 pounds each.  The mix was  85 pounds of paper, 150 gallons of water, and 1 bag of portland cement.    The papercrete website has a lot of this info on it,  www.livinginpaper.com

Here is also a youtube video that explains how a tow mixer is made and used:

http://www.youtube.com/watch?v=JoLBeV6tzJ4

Thank you for the specifics of "5 miles an hour, for 5 minutes or so".
You say "1 batch to make 18 blocks that were  1 x 2 feet in size." - can you tell me/us about how full the tank was for that batch?

- Concerning papercrete specifically: personally, unless I was dealing with already shredded paper, I would want to "Mix" it for a lot more than 5 minutes.
I'm sure the method you reference works, but I'm just particular about how I build my own place, and never want to regret not being thorough in how I mixed the concrete or papercrete, as well as what I put into it, and the whole process in general.

Here is my specific thinking about mixing something while driving to the site:
I have to get the cement and any additives somewhere anyway. What I would have is some form of trailer, so where should I put it? - may as well put it in that improvised trailer.
If its going to be back there anyway, instead of wasting gas driving around in circles (especially at today's prices) , why not just be efficient and mix it on the way anyway if its possible?
If it just will not work, oh well, but I do intend to thoroughly explore the possibility.
Also, I like the idea of picking up small loads of sawdust, manure, etc. adding water, driving to the site and mixing it on the way so that when I arrive I can pour that into a certain composting process I want to do.
Do you know or can you find out what the approximate ratio or speed of that lawnmower blade to driving speed would be? It may or may not work for concrete or papercrete, but it might be ideal as the equivalent to a huge blender for my composting needs.

creteman wrote:

Do you know or can you find out what the approximate ratio or speed of that lawnmower blade to driving speed would be? It may or may not work for concrete or papercrete, but it might be ideal as the equivalent to a huge blender for my composting needs.

Rear end ratios seem to go from about 3:1 to 4.86:1 (almost 5:1) for cars/light trucks. Tire heights from 24in. to 28in.

The formula is (from a ford parts site... first thing in my search):

RPM = MPH x transmition ratio (1 in our case) x rearend ratio x 336
          -------------------------------------------------------------------------
                              tire height

The lowest RPM would be generated by 28in. tires with the 3:1 rear end at 2160 rpm at 60 MPH and the highest with the 4.86:1 with 24in tires at 4082. So if you could reasonable drive to the site at 30 MPH you cold have as low as 1080 RPM. The added bonus to big tires being that generally they would have better weight carrying abilities as well as going over bigger bumps without sloshing the liquid as much.

You would want to take the corners really slow or the liquid would tend to go over the outside rim.... or try to lay your trailer on it's side ( a known problem with RVs which have a special hitch to help keep the trailer from tilting too much when the water tanks slosh).

The slurry was totally mixed after 5 minutes.  That lawnmower blade is chopping thru it really fast at 5 mph.

I don't know how full it was.  We put water in a 4 foot trough to approx 18 inches high.  He said this equaled 150 gallons of water.  Then added 85 pounds of paper and 1 sack of portland cement.

When we drained it into the forms, it was thoroughly mixed and easily spreadable.  It was the consistency of cooked oatmeal, before it sets and gets thick.  It poured out easily, yet set up enough to remove the forms in 20 minutes without losing it's shape. 

We'll be making our blocks on our property, and to make them quickly, get into a flow of mixing, towing, pouring into forms....and while the papercrete is setting up in the forms, mixing another batch, towing...etc. 

Using that formula, I can come up with 1500 RPM by driving down the road at a good clip.  By comparison, Kitchen Aid food processors operate at 1750 RPM.

but your kitcheaid does not have a 2-3 foot blade its more about blade tip speed (rpm*1/2blade length) than rpm if your car has a tach this type of tow mixer will produce pretty close to the same rpm as your motor runs in fourth gear at any given speed

And the food processor has a lid.... it will not start till the lid is locked.

I've come up with two simple mixing methods that eliminate the need to tow the mixer. 1. Using any metal container, insert a pto driven post hole auger. Old augers with broken tips are cheap. A lawn mower type blade could be attached to the base. This would use less gas and spilage would be less likely. Most pto augers will deliver far more power than the diferential could. Tractor mounted augers are common and not expensive. If the farm is has a tractor, there's usually an auger. Using this method simply uses something already widely available and infinately useful. 2. Suspend a hand held auger over the tank. Just enough gas can be added so the machine quits automatically when a batch is done. A suspended auger would be steered with the tortion bar. A string would connect to the kill switch and a remote throttle would be handy. This would allow the use of any puncture proof container with the auger being the only cost. $200 all in for a good used unit. And most of us need to install posts as well. I'm currently considering a Little Beaver 11 HP. hydraulic unit. The power pack can run wood splitters, cement mixers, jack hammers, tampers etc. It is reversible so if anything gets caught on the blades it's easy to clear. The unit in the photo could be run from beside the tank and locked in place if desired. A pipe sleve with a top spiggot turns it into an Archemendes screw pump so material could be pumped .

You don't want to tow it from town mixing.

A: You don't want to make a trip to town for each sack of cement.
B: I suspect that you can overmix.
C: Since the seal leaks, and 'bondo' was mentioned for sealing, everytime you hit a decent bump, you are going to start leaking again. This will not get you in good graces with the highway patrol.
D: If you ever spill a load on the road, you've got a hell of a mess, and the shovel is back home.
E: The force on the mixer blade goes up with the CUBE of the speed. 60 mph has roughly 2000 times the force on the blade as does 5 mph.
F: If you don't wrap the blade into a pretzle, you are likely to entrain a LOT of air into the mix. This may keep it from draining properly.

While the mixer from a differential is a good idea, I would rather have it stationery.

Tow it to the site. Jack up one side.

Rig up a horizontal shaft lawnmower engine to drive the lifted wheel. (Note: this won't work if it is a limited slip differential.)
I'd suggest a lawnmower wheel.

Most gas engines run about 3000 rpm, which is likely too fast. Some can be throttled back.

Alternative 2:

From your wrecked car, use the front wheels for the trailer, and use the differential the way it was meant, as a speed reducer. This will also put the tank higher which makes gravity your friend for making your pour. The engine likely is *still* too fast.

Alternative 3:

Block up your riding lawn mower and put the drive wheel in contact with the blocked up trailer wheel. This gives you some speed control.


Alternative 4. Use a 1 horse electric motor and a belt drive to the jacked up wheel. This has the advantage that you can put it on a timer. Mix for 5 minutes and shut off.


If you have a stationery mixer:

1. While you are mixing you can be doing other things -- like stripping forms.

2. Perch one of those 250 gallon caged white tanks on a stack of railroad ties, and you can be filling that tank with the garden hose while mixing and forming the previous load

A mobile mixer does have the advantage that you can unloS the mix close to your forms even if you are processing dozens of loads a day.