Papercreters: [papercreters] Re: MIXERS;

Saturday, March 24, 2012

[papercreters] Re: MIXERS; - lawn mower engine?

Isn't it easier to drive the blade direct, and just not add paper until the motor's running.

--- In papercreters@yahoogroups.com, "JayH" <slurryguy@...> wrote:
>
> This post will probably state the obvious to many who have dealt with engines, but it is worth posting to help those that may not have considered all the details.
>
>
>
> The single biggest issue with using ANY internal combustion engine is initially applying power to the load from a standstill.
>
> In a car, this is accomplished by slipping a clutch at the friction point (for a manual transmission) or a torque converter (for an automatic transmission) to gradually apply more and more power until the engine is completely directly coupled to the load (the wheels). If the power is transferred too abruptly the engine will stall, as everyone who has popped the clutch in a manual transmission car is very familiar with.
>
> A papercrete mixer presents a similar challenge. Instead of an engine driving wheels, the load being driven is a mixer blade pushing against a bunch of wet paper, usually in big chunks.
>
> With a standard tow mixer configuration, we can take advantage of the tow vehicle's clutch or torque converter to ease the transfer of power from a stand still, to fully engaged and in motion. We do it all the time when we drive, and we would still use a clutch when towing a mixer.
>
> If someone wants to use a lawn mower engine, you will still need to address the need for a clutch.
>
> Many small engine powered devices employ a cengrifugal clutch. String trimmers and chain saws typically employ this type of clutch. They work differently than a car's clutch. There is no clutch pedal or lever, but it should still work rather well for a papercrete mixer. There would be no "clutch pedal" per se, but how fast someone revs up the engine determines whether or not the clutch is engaged. If the engine is idling at a slow speed, the clutch is disengaged from the load allowing for easy starting of the engine. As the engine is revved up, the clutch begins to apply some of the power to the load, beginning to spin the blade. As the blade spins faster, eventually all the power from the engine is being applied to the blade.
>
>
> One could also use a more standard vehicle clutch or a motorcycle clutch where the operator controls the clutch directly without drastically revving the engine.
>
>
> One final "poor man's" clutch is to use a slipping belt drive. The drive belt between the engine and a pully driving the mixer blade is left loose while the engine is started, and then once the engine is running, a lever of some kind tightens the belt slipping it against the pulleys until the mixer is up to speed. This system can be very effective, but it is very hard on belts. Expect to break a lot of belts and replace them frequently. Expect loose belts to fall off frequently as well. You'll want to have a good belt guard to prevent fingers, arms, legs, loose clothing, dogs, cats, children, or stray paper getting caught up in the belt. At the same time, you'll want the belt guard accessible enough to change out belts as needed.
>
>
> Lastly, there is the option of not using a clutch at all, but using a hoist of some kind to lift the mixer blade completely out of the mixer tank. This allows the blade to spin free and easy while the engine is started. Then the blade is gradually lowered into the mix as it is spinning. This option can work very well, but it has drawbacks. It's potentially very dangerous because the operator is probably going to be very close to the spinning blade as he raises and lowers it. Also, papercrete slurry will tend to fly everywhere as the blade begins to enter the mix, and right after it is removed. With appropriate design of the lift mechanism, and extreme care by the operator, this method can work safely. Eli Sutton used this technique and posted photos of his efforts.
> http://groups.yahoo.com/group/papercreters/photos/album/2081614419/pic/list
>
>
>
> Whatever method you choose, the goals are the same. Safety should obviously be paramount. After safety, the goal is to transfer the power from the spinning engine to the papercrete slurry gradually enough to avoid stalling the engine.
>
>
>
> With some type of clutch or other mechanism to ease the transfer of power, a lawn mower engine should work very well in a papercrete mixer. Just be sure one does not try to mix too large of a mixer tank of thick papercrete slurry with too small of an engine.
>
>
> I hope this helps.
>
>
> --- In papercreters@yahoogroups.com, indiakarl <indiakarl@> wrote:
> >
> > perhaps it's already been done, but i was thinking that a vertical shaft lawn-mower engine might make a suitable power source for a non-towed mixer. old lawn mowers are readily available for pretty cheap. mounted the flange of the engine base to a couple of 2x4's so it will sit across whatever you want for a mixing drum. a shaft welded to the downward pointing drive shaft of the motor with a blade on the bottom - what ever length/depth you need for your drum. you might even go with a shaft that has a keyway that fits the drive end of the motor, so you could take off the mixer shaft. you could have a small "pulping" blade that would thrash the paper/carboard material to pulp, then a larger blade that would be good for mixing in the concrete. i'm home in thailand at the moment. haven't seen a conventional lawn mower in the 10 years i've been coming here. but they do have an abundance of hardworking Diesel engines that they use for "iron
> > buffalo's", e-tan farm trucks etc. they have pulleys on the engine that they run drive belts off of to work irrigation pumps, pond pumps, threshing machines tons of things. a mixer could easily be powered by one of these: http://www.siamkubota.co.th/ (website is in thai, but you get the idea of the engines) didn't get to it this time at home, but next winter when i'm here, i want to build a "cool room", a small airconditioned room so the family has relief from the heat in summer season - obviously needs to be a well insulated building so we don't have a spend a small forturne on electricity and an air-con unit. PC would be ideal. i'm going to experiment with using rice hulls - another thing they have in abundance here. i can get a giant bag for 5 cents.
> >
> >
> > --
> > :::karl::: : : : : : : :
> > read ThaiCountryLife
> >
>