Jay, I don't think it's relevant how long it takes to charge a battery, or 8, or whatever.
We have a very SMALL system, so small that we have our fridge on a timer so it only runs a few times a day or once a day in winter.
However, we frequently have EXCESS power in the afternoon. So that's when we run the food processor to make fudge, the skill saw to cut firewood and the washer. Speaking of which, be just fried the second Maytag washer after running some old full size washer for years without problems. It seems that the Maytag waterpump or moving to the spin cycle caused the problem as washing was fine.
We've tried running it off the 3000 watt generator, the inverter with the generator charging the full batteries and whatever else we could think off, on sunny days while the solar panels were also charging ... still no go for the Maytag.
So the bottom line seems to be the INVERTER. Our 3000 watt inverter just won't do it. We got a small Toshiba washer now that runs fine.
We also can't run our 1/2 hp water pump for the house water off the inverter unless we repeatedly try and eventually the pump will come on before the inverter overloads. We obviously only do that in emergencies when the generator won't run.
We have a little 400 watt electric mixer I got from Harbor Freight years ago thinking we might use it for small jobs. We used it to "clean" caliche rocks and used the clay / caliche to improve the adobe mix on days when the batteries were full. Only had to run it a few minutes at a time and then we let the rocks soak some more.
Last fall I put some shredded paper in the mixer for some papercrete testing but it got cold and well, it still looks like shredded paper and it would take FOREVER to build anything with that mixer. Maybe if we had some blades welded on it would work better.
The stucco guy had a full sized mixer he ran of a little generator all day long, but gas isn't cheap these days.
I don't know about RPMs and torque, but we've learned some hard lessons with the washers and obviously STARTING any mixer filled with paper or worse, cardboard, is going to be the tough part.
Anyone off grid SHOULD have plenty of extra power on sunny afternoons and it's not like we need a lot quickly, but we'll start looking for a trailer as Terry has. Not ideal here either since the roads SUCK, but it seems like still the best option.
At 05:40 PM 3/17/2012, you wrote:
You make an important point, but that point only applies if someone needs to make a large amount of papercrete quickly.
The size of the power source needed to charge a battery pack is mostly related to how fast you need to charge it. I'll make a couple of extreme examples to illustrate my point.
You used the example of solar, which is not necessarily the cheapest alternative power source for an off grid situation, but I'm comfortable exploring that option.
Let's assume that one panel will charge one battery given one full sunny day. (I want to avoid getting into a discussion over what specific size or type of panel is best or what type of battery, charge controller... blah blah blah. While that data can be important in designing a solar electric system it is not the topic we are discussing. I'm trying to keep things simple.) If one panel can charge one battery in one day. 8 panels should be able to charge 8 batteries in one day. Or one panel should be able to charge 8 batteries in 8 days.
If someone is willing to wait 8 days for batteries to charge back up, then one solar panel can be adequate to charge an 8 battery pack. This assumes 8 straight days of sunshine. My point is that if someone is willing to be patient and wait for the power to accumulate in the batteries, a smaller power source to charge them can be used.
You are factually incorrect about the torque output of an electric motor at zero RPM. A DC motor can exert large forces on it's shaft even if the load connected to the motor is so large that the motor cannot turn it and stalls the motor. No internal combustion engine can do that. When an engine stalls, it stops producing any power or any torque. Remember, John Wayland's Drag Racer has no transmission. It has no clutch. The motor is directly attached to the drive shaft. His accellerator either applies elctricity to the motor to make the wheel's go, or it doesn't. The car wouldn't be able to get going from a standing stop if the motor had zero torque at zero RPM. The opposite is the case. The motor can exert etraordinary torque at zero RPM. That is exactly why John Wayland's White Zombie Dragster can consistently beat internal combuston powered cars in short sprints.
You don't have to take my word for it. Trust the brainiacs at MIT.
I could quote 100's of other sources on the internet if you want me to.
I assure you that whatever torque your diesel engine can provide at it's best, that can easily be overpowered by a DC Electric motor properly powered.
Where an internal combustion engine has a huge advantage over an electric motor is in endurance and rapid replacement of energy reserves in the energy storage device. An electric motor needs it's batteries recharged when energy reservs run low, and that typically takes significantly longer than refilling a fuel tank. You won't see John Wayland trying to race his Datsun in a 1000 mile race for this reason (and several others.) His car is fantastic in short sprints. It is a Drag Racer, not an endurance racer.
I want to repeat the points I was making when I began discussing the possibility of an elecric mixer a long way back in this thread, perhaps wording them better. Each type of mixer can have its advantages and its disadvantages. Some mixers are great in certain situations but not others. It is up to each individual builder to decide what will work best for their own situation. While a tow mixer is a very nice design, it is not always the best for every situation.
A tow mixer, for example, is particularly great for pouring papercrete blocks. Being able to tow the mixer directly over the top of the forms laid on the ground to fill them and letting gravity do the rest makes a lot of sense. I cannot think of a more simple way to accomplish that task. Simple usually is best. However, as you pointed out in a previous post in this thread, making blocks, turning drying, stacking, the mortaring them into walls is a very large investment in manual labor. The whole ordeal of building with papercrete blocks is a complex operation of many steps. You handle the papercrete multiple times by hand. It's probably the single most labor intensive form of papercrete construction. Not for the weak of heart as you pointed out.
If someone is not making blocks, but wants to slipform or pour papercrete into forms the full height of the wall, a tow mixer loses that fight with gravity that it takes advantage of when pouring blocks on the ground. One can resort to more manual labor to haul buckets of slurry up to the form, but there is no particular advantage to getting your mix from a tow mixer vs any other mixer in that situation. Bucket shlepping is hard manual labor. If someone can use a trash pump to pump the slurry to the forms, that makes a huge difference, but again the trash pump doesn't care whether the slurry is getting pumped from a tow mixer or another type of mixer.
I would rather invest my time and effort into building a machine that can reduce the amount of manual labor I have to expend to a minimum, as well as minimize the amount of money I spend on building and powering it. I want to do more with less. More building with less work, less money, less energy, less wasted effort, less injuries, less stress.
It's not that I'm afraid of hard work. I work hard frequently, but I'm no masochist. If I can find an easier way that makes sense, I won't torture myself just for the heck of it, I'll be all over the easier method. That doesn't mean I think those that build with blocks are wrong or are masochists. They are doing what works best for them, I respect that. I applaud their efforts and root them on.
I simply have a desire to push the boundaries of what is possible. I want to always work to improve what we do and how we do it with papercrete. That's why this group was created.
If I can create a new mixer and a new technique for construction that might work well for myself and maybe some other builders, I will consider my efforts a great success. If I fail, but I learn something, and share my failure with everyone else, and they learn something, that too will be a success, albeit not as big of a success. If I try and fail, and that entertains someone so that they can say, "I told you so," I'm okay with that too. I'm a big boy. I can handle it. Perhaps what I share will inspire someone to an even better idea and come up with something completely different that works better than anyone has imagined. I would love that too.
Compounding a failure by not learning from it is the worst thing we can do on Papercreters. We should be celebrating those willing to admit their mistakes and share them with us, so we all can learn how to avoid the same mistakes. I may turn out to be the biggest failure on the group. If everyone learns from it, then at least my efforts will be good for SOMETHING.
--- In email@example.com, Donald Miller <donald1miller@...> wrote:
> Jay, you won't get any argument from me about the torque output of a series wound DC motor. The problem with using this in an off grid situation is providing the power to run it. These motors take a lot of current to operate and therein lies the problem. To provide the power to run these motors would require a solar panel array and battery bank of such size that the cost to purchase said panels and batteries would be terribly cost prohibitive. And you are somwhat confused on the torque output of diesel engines. One of their strong points, at least in a small truck, is that they deliver a lot of torque at a low rpm. My Dodge 4X4 3/4 ton pickup runs at 1700 rpms at 65 miles per hour. And, true, a diesel engine puts out zero torque at zero rpm, but so too does the electric motor. If the motor isn't turning it can't put out any torque. My tow mixer is on the small side, 160 gallon tank and let me tell you takes a lot more than "measly" power to operate it.
> Even a tow/stationary mixer made from a 55 gallon barrel would require a large motor to operate it and that large motor is going to require a lot of DC current to run on.
Saturday, March 17, 2012
at 8:10 PM