Mutant vehicle - figuring horsepower required?

falk · Post by **falk** » Fri Sep 19, 2008 12:09 pm

So I'm seriously leaning towards electric. Simpler, less to go wrong. A 10 hp brushless DC motor seems ideal, and there are several available. Lots of good info at http://www.thunderstruck-ev.com/

an Etek motor would have been ideal, but they're out of production.

Problem: they're bloody expensive. After motor, controller, charger, batteries, and transmission, we're talking around $2k. Too much.

I'd love to just buy a big motor off of eBay, but I know almost nothing about motors and have no idea where I would proceed from there.

Has anybody else used electric? What solutions did you find?

gyre · Post by **gyre** » Fri Sep 19, 2008 12:21 pm

falk wrote:
gyre wrote:I've used timing belts for years at a steady 10,000 rpm shift point.
I'm not sure I understand the lingo. "Shift point"?

Engine rpm when shifting gears.

2005 seemed really dry.
2006 was pretty damp, relatively speaking.
Still drier than you can get it here with ac.

falk · Post by **falk** » Fri Sep 19, 2008 12:59 pm

Ahh. I wasn't planning to shift any gears; 5 mph will be my top speed.

motskyroonmatick · Post by **motskyroonmatick** » Fri Sep 19, 2008 2:33 pm

I think this project done by two guys in canada might give you some good ideas to pick and choose from.
Their not yet complete website.
http://forkenswift.com/
The blog where they detail the conversion of Forkenswift.
http://ecomodder.com/forum/showthread.p ... ft-33.html
I think using the electric hydraulic pump motor off of a fork lift might be the way to go. If you managed to get your hands on an entire forklift like those guys you could rob basically everything you would need to control the motor rpm which would give you much smother starts than an on off control. Then sell the remainder as scrap.

My thoughts on using an electric motor was to use an AC one and couple it directly to the front of a manual transmission. Gear selection could only be done with the power off and starts would be abrupt. It would also be powered by an on board generator. AC motors are much cheaper than DC due to their prevalence in industry.

falk · Post by **falk** » Fri Sep 19, 2008 3:11 pm

motskyroonmatick wrote: AC motors are much cheaper than DC due to their prevalence in industry.

Yeah, I noticed that. Typically they want 230-460 VAC to power them. How would I run one from DC batteries?

EspressoDude · Post by **EspressoDude** » Fri Sep 19, 2008 4:50 pm

DC motors typically have brushes and a commutator which adds to the cost. They will often put out twice nameplate horsepower for 10 - 30 seconds.

Ac motors are typically 3 phase. you would need an AC inverter and likely a battery bank of 240 volts to use a 230v AC motor...

motskyroonmatick · Post by **motskyroonmatick** » Fri Sep 19, 2008 5:38 pm

120 volt motors are all over the place although it is true that many run on 240 and 3phase which is much more efficient. I believe DC to 3phase converters are in the early adopter stage of things and quite expensive. I'm sure the cost would over rule that. There may be some heavy duty DC to 120 converters out there but I don't personally know where to get them. Searching around on the electric car forums would turn something up I'm sure.

Every time you run the voltage through an inverter or controller you get loss. The best bet is to keep the current type the same so if your going with multiples of 6 volts by using batteries then use a DC motor that will match up to the amount of batteries you want to use. Messing with an electric golf cart might give you a good working knowledge of how the system works and give you some ideas to make you mutant happen.
The big battle with electric cars is the sheer weight of the batteries and the fact that you have to carry all those batteries to get anywhere. Sure there are exotic batteries coming out but you can't beat lead acid and their hefty weight for cost to power ratio.

Captain Goddammit · Post by **Captain Goddammit** » Fri Sep 19, 2008 5:58 pm

If you use an electric motor and a gas generator to supply the power, you ought to just use a gas engine and save all the unnecessary complication and expense.
I'm not sold on electric power for low-budget playa vehicles. Unless you can afford or somehow scrounge up a LOT of solar cells, you're gonna need a gas generator to charge it.
And as for silently cruising the playa... well, my boat runs very quietly, and it sucks! What happens when you're that quiet is people don't notice that you're coming - like, even when you're two feet from them! It turns out that in actual practice on the playa, you WANT some noise.

gyre · Post by **gyre** » Sat Sep 20, 2008 1:40 am

That's what the bells are for, Captain.
Don't tell me you have a boat without a bell!?

Inverters are made as big as you want.
They are used for solar power in the hundreds of amps.

falk · Post by **falk** » Sat Sep 20, 2008 11:50 pm

Well, I've been pricing motors, controllers, charge controllers and so forth, and I'm convinced it will cost about $2000 to build a 10 hp electric
vehicle, not including batteries. Add another $1000 if you want a backup generator.

You can buy a used riding mower with a 20 hp engine used for about $400, so I'm starting to look in that direction.

gyre · Post by **gyre** » Sun Sep 21, 2008 2:30 am

Bigger than an electric forklift will get harder to find, but it happens.
There was a BIG dc medical motor by ge that I had a chance at and it ended up being thrown away!!!!
So cheap happens.
That motor probably cost thousands new.

Gas is probably easier to find past 2 1/2 hp.
Keep in mind the torque difference.
Mine is 9 pounds of torque.
Common type too.
Reaonable on ebay.
Much cheaper in the real world sometimes.

ygmir · Post by **ygmir** » Sun Sep 21, 2008 7:47 am

IIRC:
engine to motor equates to 3:1 as far as h.p.

falk · Post by **falk** » Mon Sep 22, 2008 11:32 am

This just occurred to me this morning. Black Rock City is at 4000 feet, and high temperatures can give an effective altitude (called "density altitude") of well over 7000 feet. According to my notes, that will reduce the available oxygen to a gas engine (or generator) by 20%

ilmarinen · Post by **ilmarinen** » Fri Sep 26, 2008 8:19 pm

Reading through this thread, it sounds like the power train from a 10-20 hp garden tractor sounds really close to ideal for a mid-size MV. I've just recently learned about hydrostatic transmissions on these things--which again sounds like the almost ideal transmission for the application. These vehicles are designed to have high torque for around 5 mph applications (snow plowing, etc.)

Does anyone know of example MV based on such? I guess I could see two paths here--first, rip apart the tractor, extend-out the axles to give a wider wheelbase and build-up a custom vehicle frame on top. Seems like axle load is a limiting factor, but maybe could take the weight into the frame off the extended axles.

Second would be to build a small/simple trailer and pull it with a (disguised of course, mutated as it were) garden tractor.

How important would real suspension be on the Playa vs. rigid axles, maybe with balloon-like tires?

I've sorta been mulling over MV ideas with some friends, so hijacking the thread a bit to throw-out some ideas.

falk · Post by **falk** » Sat Sep 27, 2008 9:14 am

For the price, I think you can do a lot better than the motor you listed. The sweet spot seems to be the Etek-R, which will produce 8 hp continuous and costs about the same. You still need a controller ($300-400), enough batteries to get you around the playa for a day ($1000), and a charger for the batteries. We're pushing $2000 at this point, and haven't even bought the axle or differential.

And you still have to run a gas or diesel generator to charge the batteries, even if you plug into someone else's electrical grid, they'll want you to chip in financially. If you buy a generator, the 2000 watt Honda generator is nice and quiet, but that will set you back another $1000.

By contrast, a 13-hp gas engine can be had for $400 and that replaces motor, controller, batteries, and charger.

Buy a used riding mower and gut it, and you've got axle and differential too.

ygmir · Post by **ygmir** » Sat Sep 27, 2008 9:22 am

And,
remember to consider total possible weight and cargo into axle/tire combos........also if it'll be mostly on one axle......
Try not to run those components at max, since, even slowly taken bumps and holes can increase the momentary load quite significantly......

unjonharley · Post by **unjonharley** » Sat Sep 27, 2008 9:30 am

The six hours to recharge for a four hour run helped me decide on gas.

So far I have picked up a 11hp lawn mower.. Now to strip it to it's frame and wash it.. Then rework all the moving part.. Clean or repair. Test run. test run for speed and change pullies if needed. Then to build the MV body over the whole thing.. It will be able to pull a trailer also..

unjonharley · Post by **unjonharley** » Sat Sep 27, 2008 9:34 am

ygmir wrote:And,
remember to consider total possible weight and cargo into axle/tire combos........also if it'll be mostly on one axle......
Try not to run those components at max, since, even slowly taken bumps and holes can increase the momentary load quite significantly......

This year there were a lot of MV's with outrigger axels/wheels.. Saw a couple that were bent also..

ygmir · Post by **ygmir** » Sat Sep 27, 2008 9:37 am

outriggers are great with a caster pivot setup.......as long as they're actually strong enough......

a lot of people don't consider the whole "height/width" thing..........

LeChatNoir · Post by **LeChatNoir** » Sat Sep 27, 2008 10:21 am

Buy a used riding mower and gut it, and you've got axle and differential too.

Thatâ€™s an idea so beautifully simple that it didnâ€™t even occur to me. Shows how my mind works sometimes, I suppose.

I guess I could see two paths here--first, rip apart the tractor, extend-out the axles to give a wider wheelbase and build-up a custom vehicle frame on top. Seems like axle load is a limiting factor, but maybe could take the weight into the frame off the extended axles.

That hit me too. You could put some extra support bearings out near the wheels, but that axle still seems small for anything really giant.

This just occurred to me this morning. Black Rock City is at 4000 feet, and high temperatures can give an effective altitude (called "density altitude") of well over 7000 feet. According to my notes, that will reduce the available oxygen to a gas engine (or generator) by 20%

It makes a noticeable difference. We started the Contraptionâ€™s engine up after getting back just to confirm this and you could tell it had more pep than when on the playa. Iâ€™d say 20% drop seems to â€œfeelâ€

ilmarinen · Post by **ilmarinen** » Sat Sep 27, 2008 11:22 am

LeChatNoir wrote:
That hit me too. You could put some extra support bearings out near the wheels, but that axle still seems small for anything really giant.

Yeah, I'm thinking medium-sized vehicles--6 person? The axle ratings on the smaller hydrostatic garden tractor transaxles is around 700 lbs , but, also, Tuff Torque makes one for the heavier "utility" vehicles that has 1850 lb static rating:
http://www.tufftorq.com/prods.asp?PID=21
Think that could be found on a number of used vehicles out there. It's big and expensive compared to their smaller garden tractor transaxles:
http://tinyurl.com/53ojxm

On the other hand, having the bigger model with a PTO could be handy for attaching an alternator to, etc.

Big advantage of the hydrostatic is you can run a small engine at max power or torque, at a set RPM, and use the hydrostatic transmission for infinitely variable speed (gear ratio).

But really, once you have extended the axle such that it's just transmitting power to wheels that have separate bearing directly attached to the vehicle frame, the only question is weather you exceed the torque rating for the shafts, right?

-B.

gyre · Post by **gyre** » Sat Sep 27, 2008 11:35 am

I don't think you can buy an equivalent quality gas motor as cheaply as electric.
Electric is much easier to buy used and get something good too.
It just depends on what you want.
There are 12-48 volt motors out there.
Hubmotors start at about 100 watts though I think 250 is the minimum useful.

You want the highest voltage you can deal with.
Some hubmotors have no controller really.
A good controller does much more than control starting.

I will be using 36 volts and charging with a 12 volt charger or chargers.
Charging while running might be easier at series voltage though.

My motor is a 2 and 1/2 hp/ 9 lbs GE about 60 pounds mass.
Curtis controller.

There is a formula for altitude/horsepower.
My car gained 90 hp from denver to sea level.
The formula used was more complex that just % but worked out to about 20-25 % in this case.
I think displacement is a factor.

MikeVDS · Post by **MikeVDS** » Sat Sep 27, 2008 12:05 pm

Electric is easier. I don't know if it's really "cheaper".

With electric you need to buy deep cycle batteries which can be costly. You also need a generator and you'll have to run it when it's parked, which can be a pain. You'll also likely use more gas running your generator.

You can buy a "totaled" car and fix it up pretty cheaply also. I went back and forth on what I wanted to do this year and I'm going with a VW buggy. It's tried and tested and I'll know what it can handle. Also just filling up with gas seems so convenient.

gyre · Post by **gyre** » Sat Sep 27, 2008 12:10 pm

At that range of power, gas becomes cheaper.
I was mostly referring to state of the art vs more primitive gas designs.

unjonharley · Post by **unjonharley** » Sat Sep 27, 2008 12:19 pm

Couple of years ago an airstream village poped up across the way from our camp.

As they arrived they unhooked and used a small electric mule to park the trailers.. It was like two wheels and a electric motor with a ball hitch..

Traction? aside, Something "like" this in size could pull a large load.

ygmir · Post by **ygmir** » Sat Sep 27, 2008 1:21 pm

one thing to consider, though, in pulling is that the 'tractor' needs plenty of traction......which either means weight or surface area........and tread design

LeChatNoir · Post by **LeChatNoir** » Sat Sep 27, 2008 9:29 pm

ilmarinen wrote:But really, once you have extended the axle such that it's just transmitting power to wheels that have separate bearing directly attached to the vehicle frame, the only question is weather you exceed the torque rating for the shafts, right?

-B.

I'd think so.

And if you had to extend the axles for some reason, you might have issues with torsion but that could be overcome by using a larger diameter shaft for the extension and support bearings along the length and/or near the connection.

falk · Post by **falk** » Sun Sep 28, 2008 1:21 am

LeChatNoir wrote:
This just occurred to me this morning. Black Rock City is at 4000 feet, and high temperatures can give an effective altitude (called "density altitude") of well over 7000 feet. According to my notes, that will reduce the available oxygen to a gas engine (or generator) by 20%

It makes a noticeable difference. We started the Contraptionâ€™s engine up after getting back just to confirm this and you could tell it had more pep than when on the playa. Iâ€™d say 20% drop seems to â€œfeelâ€

ygmir · Post by **ygmir** » Sun Sep 28, 2008 5:26 am

falk wrote:
LeChatNoir wrote:
This just occurred to me this morning. Black Rock City is at 4000 feet, and high temperatures can give an effective altitude (called "density altitude") of well over 7000 feet. According to my notes, that will reduce the available oxygen to a gas engine (or generator) by 20%

It makes a noticeable difference. We started the Contraptionâ€™s engine up after getting back just to confirm this and you could tell it had more pep than when on the playa. Iâ€™d say 20% drop seems to â€œfeelâ€

falk · Post by **falk** » Mon Sep 29, 2008 9:17 pm

Colonel Monk wrote:BTW, I wasn't saying that I think you're pursuing the wrong idea, only that there are other alternatives.

Yeah. I really, really want to go with electric, but the cost and weight seem prohibitive. I'm going to try attending some meetings of the local electric car club for more ideas.

Agreed, there are probably cheaper e-motors out there, but the eteks are gone now AFAIK.

Yes. The Etek-R and Etek-RT are someone else's product. They're brushed motors in the same form factor as the original Etek. They're brushed, so not as elegant as the original Etek, but the controller might be cheaper, so that's a plus.

So, I know that a simple gas motor is simpler, but I'm looking to try it this way. I've seen MVs on the playa doing it, but never asked them how - this year though didn't see any running on little genny only....

monk

The giant tricycle "Daisy" ran on gennie at night, or during the day once the batteries were exhausted. I think it used one of the EU 2000 hondas.

Mutant vehicle - figuring horsepower required?

Another thought: need to account for thin air

Garden Tractors