Low Speed High Torque Drive?

[JHale]

Hey all!

In a project completely unrelated to FIRST, I have a question about putting together a high-torque drive.

Here is the context: My goal is to have a robotic (in a few years maybe autonomous) snowblower...yeah. I got my hands on a HUGE 10hp 5x3' impeller Craftsman, its ancient but it kicks major snow butt!

I am trying to work out the design for the drive right now. There are two options:

1. Electric drive run off battery/generator combination.
2. Mechanical drive run off the existing input shaft.

The first is easy, but what is a good motor/transmission combination? Money is definitely a factor, I can't really spend more than $250 or so per trany. Remember that I am trying to replace a 10hp motor in this case.

The second I would imagine to be more effective but way more complicated. I would need two transmissions (one for each drive wheel) that would have forward and reverse. I was thinking planetary with clutches but its a complicated approach.

What are your thoughts?

Some tech:

12" drive wheels in skidsteer type configuration. (The rest of the blower just scrapes along the ground)

[AdamHeard]

The cost here seems to be the biggest issue; even if you get some big, powerful, motors on the cheap, the controllers sure won't be.

I don't have any links on hand, but there are many "surplus" sites that may have motors to suit your application. A lot have gearboxes already on them for various applications, so I think getting lucky and finding a good motor/gearbox combination would be your best bet.

Robot Marketplace has a lot of random motors people have used to power heavyweight (320 lb) combat robots, so something there probably is powerful enough to power your snowblower; especially since you'll be gearing down substantially. The problem is, for the big boys you need some serious cash; and most are just motors, no gearboxes.

I'd say if you have work with a team, see if you can find a way to do it with small CIMs. Crunch the numbers and do some tests to see how much power you really need to drive it, and see if a pair (any more than 2 and the implementation get's clunky fast, as you can no longer use a COTS gearbox) geared real low will cut it.

[Brandon Holley]

a company in japan has made autonomous snowblowers...if you research them you may be able to see what they came up with

I don't remember the company but some quick google searched should turn it up.

[JHale]

Forget the controllers for now in price. I'm looking for both transmissions and motor sets for sub-$600. Electronics will mostly be donated, so I'm not worrying about that right now.

http://www.robotmarketplace.com/products/0M-E150.html

Any thoughts on that motor in a ~200:1 ratio transmission (I'm planning on using belts)?

What about the CIM motors that come in the KOP, they are cheap, but do they have the power?

[artdutra04]

I wonder how feasible it would be to use the 10hp engine to drive the snow blower itself while throwing snow?

I'm assuming the snowblower is a half-track with skid-steer for turning. If that's the case, then attach two pulleys to the engine output shaft for non-toothed timing belts. The reason why non-toothed timing belts would work well here is because if use a linear actuator to dynamically tension them, you can let off the tension and the belts will slip. This allows you to have a variable "clutch" to engage power independently to each of the tracks.

Now that the power is delivered to the wheels, you need a way to select direction. On each of the tracks, mount a gearbox inside there with a mechanical means to reverse the output direction, such as a dog- or mesh-shifter that shifts between two sets of gears with the same ratio but opposite output direction.

Since servo motors can be used to power the dog-shifters, and a simple relay switch can power a linear actuator, there is no need for complex electronics or even an onboard generator*, since neither of these will draw much current. Something such as a 12v FRC battery (or two) or a custom pack made from Li-po cells should provide more than enough power for hours of run time.

* Although if you want a small generator to trickle charge the battery, this is the perfect scenario for a Sterling engine: hot engine + cold air. You can also mount Peltier thermoelectric coolers there to use this huge difference in heat to act as thermogenerators, although the efficiency will be low.

[Tom Line]

If you use an electrical system to drive it, you're going to want a charging system as well. Batteries don't like the cold, and bad things might happen when your control system dies but your snowblower keeps going.

Come to think of it, you're going to want a charging system anyway. Even if you were to power it from the 10hp motor, you'd need gearing and a clutch system that would likely be electronically engaged.

Is this a pull-start, or does it have an electronic ignition and a battery already onboard?

[MrForbes]

see if you can find an old riding mower to swipe parts off? they usually have a transaxle driving the rear wheels, with a belt pulley on the input side.

(if you want the one in the picure, let me know....it's free....)

[JHale]

@artdutra04:

You're 90% right, except its wheels instead of treads. Right now they are attached to a single axle that hits a 5 speed transmission etc. The pulley system is actually how the existing clutch works.

The idea with it being driven by the engine would be to split the output to two transmissions.

@Tom Line:

The engine does a nice job of keeping everything toasty. If I pack the batteries where I plan to (essentially right under the engine) I am sure there will be no temperature problems.

Its an electric start. The onboard battery is a joke though. Its charged off the alternator.

@Squirrel:

Thats the way it is driven now. To turn it you have to lift the front of the ground and just use yourself.

[JHale]

I just had a thought:

What about picking up a used power chair? That gives me two motors+transmission+speed controller. I can do a little custom gearing if I need to, but it could solve a number of problems.

Thoughts?

[spazdemon548]

One option you have not considered is a hydraulic drive. I am not to familiar with them, but you will be getting speed control, forward/reveres, and its likely that you could direct drive right off of the hydraulic motors with no transmission needed. As far as electrically actuated valves go though, I wouldn't know where to start, and they might draw enough that you'll still need that alternator.

[JHale]

@spazdemon:

Way out of my price range. A small vane motor alone is about $600, I would need two along with all of the flow control mechanisms and the pump.

[DonRotolo]

You're using the gasoline engine to drive the impeller, right? All you're looking for is a way to steer the thing, since it already moves forward under its own power.

In that case, go after the problem: Steering.

Some ideas:
Mechanically brake one wheel or the other (is there a differential?)
Put a third wheel or track on to positively steer it
Drive one wheel electrically, and stop the other wheel when necessary (the electric one can run backwards...)
Ditch the auger and put a propane flamethrower on it.. (eh, scratch that one...)
I'm sure you can think of more.


It seems to me that making it track straight is an issue. I know that when I use my 7 HP blower, I have to wrestle with it to make it go where it's aimed - sometimes.

Oh, and in any case, put a fail-safe kill switch right up front, so if it's coming after someone they can whack the switch and kill the ignition or something. You never know.