Mutant vehicle - figuring horsepower required?

gyre · Post by **gyre** » Wed Sep 17, 2008 11:13 am

I think torque may be more important than horsepower.

A lot of small motors are designed for a lighter load than you are planning on.
Under worst case situations, this may cause bearing wear, or catastrophic failure.
With drivetrains I think they call it stall load and it is carefully calculated for axles and so on.
This usually doesn't come up until you start making these types of radical engine changes and taking a 75 mph motorcycle engine and running a heavy load at slow speed is one.
An issue I ran into is that smaller bikes have barely functional clutch and trans for their weight to start with.
You have to get to the 600 cc to start getting decent parts, even if you don't need the power.

I'm still not sure I understand all you're trying to do.

I am wrestling with the 4500 mile commute too and I am working on a compact to VERY compact design.
A larger vehicle may be better stored closer to Reno.

If you can, start with an adequate chassis to start with.
8 people is a lot.
You could start with a golf cart or small car base and use a trailer.
Or some other small vehicle, tractor, etc.

For electric, golf carts and fork lifts have the best motors for the money in your size range.
My 2 1/2 hp has 9 pounds of torque.
And they often come with great controllers.

I don't think a locked axle is an issue on the playa unless you have grippy tire.
May annoy you.
I've driven them on the street.

MikeVDS · Post by **MikeVDS** » Wed Sep 17, 2008 12:01 pm

It's about torque and horsepower. Friction and the playa are going to eat up some horsepower so you need enough to keep up with your resistance at 5mph. HP also determines acceleration rate. You also need enough torque to get you moving. You could move around the playa with a 1/1000 HP motor that is geared way down. You may take a year to go a mile, but you can move with really small motors. This is why there is no correct answer except for what is acceptable to each person. Some people may be willing to crawl along the playa.

From 0 to 5mph you probably don't want multiple gears. You're going to want to figure out the circumference of your tires and multiply it by the RPM of your tires. That's the distance you'd ideally travel in a minute. 50% loss might be a decent estimate. If you gear for 10 or 15 mph you'll lose torque (slower acceleration and lower max load) but you'll assure that unaccounted friction and losses won't prevent you from reaching your 5mph limit.

If you're going with automobile parts, just look at the vehicles that use the motors and compare capacities.

Captain Goddammit · Post by **Captain Goddammit** » Wed Sep 17, 2008 5:55 pm

geekster wrote:Often the alternator one has is really powerful enough, the problem is that people cruise around at little above idle and the alternator never gets to its optimum RPM. The field current is higher in order to keep up the power level at low RPM and that causes hotter internal temperatures than normal and can result in premature failure of diodes and windings. The trick is to get the alternator spinning faster at lower engine RPM, same with the water pump. These are the same tricks used for parade vehicles. Overheating and low alternator output is a problem with them as well. This is particularly true at night with headlights and other power drains for illumination, music, etc.

A larger main drive pulley will help everything out, power steering if you have it, alternator, water pump, etc. What you want to do is increase the ratio of drive pulley diameter to driven pulley diameter. I see a lot of people out there who have alternator problems even with high output units when they might be able to use what they already have if they could get it to spin faster at low vehicle speed.

I went through this issue with my boat. The best solution (by all standards - cost, ease, effectiveness) wasn't to gear up the belt, it was to use alternators that put out lots of current at idle speed. Get a GM "CS-130" from a late '80s - early '90s small GM car at the junkyard for $10 or so. You'll be happy. Get and mount two and you'll be happier.

Captain Goddammit · Post by **Captain Goddammit** » Wed Sep 17, 2008 6:23 pm

My thoughts on the mutant vehicle in question...
A solid drive axle with no differential will make steering very difficult.
Using a skid-steer setup (manipulating the left and right brakes) will work poorly, and not at all unless ALL wheels on each side are included. Well, unless you build a three-wheeler, but making the third wheel steer would still be far superior to brake-steering, which will probably just stop the vehicle.

You need real steering! And if using a differential of some sort is out of the question, I think I'd consider just driving one wheel.

More power is better. Gyre is right about torque. The playa might be smooth, flat, and hard... or it might be bumpy and soft.

I'm not keen on the centrifugal clutch either.

When you say you've ruled out car engines as too big and heavy, have you considered something like a tiny 3-cylinder from a Geo Metro, or some other such tiny vehicle? Adequate power, available automatic transmission which makes playa operation MUCH nicer, quiet running, and you can use the whole engine/transaxle/suspension setup and get power, brakes, and steering in one modular package.

geekster · Post by **geekster** » Wed Sep 17, 2008 6:44 pm

Get a GM "CS-130" from a late '80s - early '90s small GM car at the junkyard for $10 or so. You'll be happy. Get and mount two and you'll be happier.

Agreed. I have had good luck with the units from ambulances too. They are designed to put out a boatload of current at idle but the engines on ambulances often have an "idle up" mechanism that increases the idle speed if the voltage drops while out of gear.

A source

falk · Post by **falk** » Wed Sep 17, 2008 7:20 pm

Another thought. The calculator said I need 4-7 hp. But I realized that if I use a 4-7 hp motor, then I'm using one that's just *barely* good enough to do the job. When you use parts that are barely good enough on the playa, you quickly regret it. So now I'm thinking 10 hp or more.

I looked around: a 10-20 hp motor, in the form of a riding lawnmower, can be had used for about $350. If you're willing to chop it apart, it's got everything you need from the gas tank to the differential. There's a lot to be said for that approach.

I sort of had my heart set on electric, but it will cost at least 4x the price once you add in a backup generator.

Anybody familiar with this MV:?

http://images.burningman.com/index.cgi?image=23224
http://images.burningman.com/index.cgi?image=8070
http://images.burningman.com/index.cgi?image=6232

I never got a close enough look at it to see how it was made, but this is almost exactly what I want to do for mine.

Toolmaker · Post by **Toolmaker** » Wed Sep 17, 2008 7:20 pm

Captain Goddammit wrote:
geekster wrote:Often the alternator one has is really powerful enough, the problem is that people cruise around at little above idle and the alternator never gets to its optimum RPM. The field current is higher in order to keep up the power level at low RPM and that causes hotter internal temperatures than normal and can result in premature failure of diodes and windings. The trick is to get the alternator spinning faster at lower engine RPM, same with the water pump. These are the same tricks used for parade vehicles. Overheating and low alternator output is a problem with them as well. This is particularly true at night with headlights and other power drains for illumination, music, etc.

A larger main drive pulley will help everything out, power steering if you have it, alternator, water pump, etc. What you want to do is increase the ratio of drive pulley diameter to driven pulley diameter. I see a lot of people out there who have alternator problems even with high output units when they might be able to use what they already have if they could get it to spin faster at low vehicle speed.
I went through this issue with my boat. The best solution (by all standards - cost, ease, effectiveness) wasn't to gear up the belt, it was to use alternators that put out lots of current at idle speed. Get a GM "CS-130" from a late '80s - early '90s small GM car at the junkyard for $10 or so. You'll be happy. Get and mount two and you'll be happier.

One of the reasons my design used higher output alternators is due to price and junkyard availability. Plus I plan on lightin the fucker up like a winter soltice tree.

Speaking of which.. has anyone tried those make it yerself belts? ya know the one with links of some sort.. do they even hold up?

Since this thread has so many calculators and whatnot.. here is the belt pulley page I use.

http://www.csgnetwork.com/pulleybeltcalc.html

here is where the whole plethora of calcs are listed

http://www.csgnetwork.com/converters.html

EspressoDude · Post by **EspressoDude** » Wed Sep 17, 2008 7:46 pm

don't forget about the horsepower required to run the alternators, not only to create the output power, but also to charge the field.

Some of the 100 - 130 amp alternators will take 2 - 3 hp

unjonharley · Post by **unjonharley** » Wed Sep 17, 2008 8:10 pm

EspressoDude wrote:don't forget about the horsepower required to run the alternators, not only to create the output power, but also to charge the field.

Some of the 100 - 130 amp alternators will take 2 - 3 hp

OhOh!Back to the drawing board..

I want to run the alternator off the shaft that would go to the mower blade.. I can put one hell of a pully there.. The plan is to find the running speed at an idle/low speed in the transmission. Would preffer to run in hi gear.. The Q is..Do I make the motor pulley larger or the gear box pulley smaller?? A smaller rear pulley the engine would have to run faster.. Larger front pulley is more torque on the engine.. The engine is old.. I'll go with changing the rear pulley..

LeChatNoir · Post by **LeChatNoir** » Wed Sep 17, 2008 10:17 pm

Damn, Grazeldaâ€¦

Weâ€™ve just hijacked this thread.

Throw a bunch of backyard gear-head goobers like us a morsel and weâ€™ll wool it to death before leaving it limp and soggy on the floor.

And speaking of which:

I used ab alternator on The Contraption this year and it had noticeable drag on it. Itâ€™s a good old Delco-Remy and it had an output chart listed on the body by RPM. Working strictly from memory here, but I think it listed 20 amps @ 2000 RPM and I had it geared up to about 3000 or so using noisy chain and sprockets. 60T drive to 11T on the alternator. Had to turn a special hub on the lathe to get it to work.

Oddly enough, when we got it out of the trailer back home and fired the engine up you couldnâ€™t tell if the alternator was on or off. No noticeable difference in drag on the engine. I suppose thatâ€™s the difference between 4000â€˜+ and 700â€™ above sea level.

ygmir · Post by **ygmir** » Wed Sep 17, 2008 10:33 pm

unjonharley wrote:
EspressoDude wrote:don't forget about the horsepower required to run the alternators, not only to create the output power, but also to charge the field.

Some of the 100 - 130 amp alternators will take 2 - 3 hp
OhOh!Back to the drawing board..

I want to run the alternator off the shaft that would go to the mower blade.. I can put one hell of a pully there.. The plan is to find the running speed at an idle/low speed in the transmission. Would preffer to run in hi gear.. The Q is..Do I make the motor pulley larger or the gear box pulley smaller?? A smaller rear pulley the engine would have to run faster.. Larger front pulley is more torque on the engine.. The engine is old.. I'll go with changing the rear pulley..

Be careful about using to small a pulley, the smaller ones can lose a belt easier, and, wear the belt faster........

gyre · Post by **gyre** » Thu Sep 18, 2008 2:05 am

falk wrote:Another thought. The calculator said I need 4-7 hp. But I realized that if I use a 4-7 hp motor, then I'm using one that's just *barely* good enough to do the job. When you use parts that are barely good enough on the playa, you quickly regret it. So now I'm thinking 10 hp or more.

I looked around: a 10-20 hp motor, in the form of a riding lawnmower, can be had used for about $350. If you're willing to chop it apart, it's got everything you need from the gas tank to the differential. There's a lot to be said for that approach.

I sort of had my heart set on electric, but it will cost at least 4x the price once you add in a backup generator.

Anybody familiar with this MV:?

http://images.burningman.com/index.cgi?image=23224
http://images.burningman.com/index.cgi?image=8070
http://images.burningman.com/index.cgi?image=6232

I never got a close enough look at it to see how it was made, but this is almost exactly what I want to do for mine.

For charging, hook into a big grid and chip in on the costs.

Electric has packaging and durability advantages.
Look for second hand packages and parts.
Initial cost can be higher with lower maintenance and power costs.
If you go large enough, gas begins to be more cost effective.
The primary reason to use electric is the surreal experience of gliding silently along.
Try it before you nix it.

I find an electric bike very pleasant even if I have nowhere to go.
I plan on setting one up for default and when I switch to lithium iron from lead, at current prices I would spend about +$2,000.
But cost per mile would be pennies on the ac grid after that.

Grazelda · Post by **Grazelda** » Thu Sep 18, 2008 9:13 am

LeChatNoir wrote:Damn, Grazeldaâ€¦

Weâ€™ve just hijacked this thread.

Throw a bunch of backyard gear-head goobers like us a morsel and weâ€™ll wool it to death before leaving it limp and soggy on the floor.

please hijack away LeChatNoir... i am sucking in brain mojo with every post. some of the posters are my "playa heros" and fear if i reply too quickly i might get horribly snarked by one and my tiny little ego will be peed on. not all together a non-healthy thing in itself, but akin to getting a deep colonic from a pissed off LEO.

only advice things i am firm against are the use of a repurposed car/truck (weight, steel, and haul back), and using a repurposed golf cart (WAY more mondo amps than i would be able to replienish), and making it pedal powered (too old, pudgy and lazy to survive the experience smiling).

gyre · Post by **gyre** » Thu Sep 18, 2008 9:36 am

Golf carts, gas and electric are very efficient for carrying a lot of weight, not so much for a light package.
I don't see how you can carry what you propose with less power.

If you want to avoid car parts, there are many ultralight engines, many in cars.
The question becomes how much weight and how much do you want to spend?

Scat makes an aluminum V4 based on the Chevy V8.
Very cheap for the weight and very compact.
Mates to all gearboxes too, I think.
After the Scat, they start getting lighter and more expensive.
Turbine would be the lightest.
There is an 8hp model.

Is packaging a factor?

Will you re-use the drivetrain or burn it all?

Does noise matter?
Vibration?

Auto trans with fluid drive can help with the shock and stall load problem I mentioned.
Some bike engines can produce more power than the engine can actually survive under constant load conditions.

unjonharley · Post by **unjonharley** » Thu Sep 18, 2008 10:16 am

Slipping the clutch on a lawn mower power frame will not damage it.. It is not a clutch.. It's a belt tightener.. Slipping will be necessary to climb over the dunes at low speeds.. I figure on using the deck lowering lever to add a hand clutch.. The leg is less steady..

Saw a 18hp lawn mower (pretty new) for 60$ on Craigs List.. The front end was collapsed.. Other from that the owner said it was ok.. !8hp could go a long way.. just shopping

Grazelda · Post by **Grazelda** » Thu Sep 18, 2008 10:22 am

<compliment>gyre, you have a way of pelting folks with reality facts that is sometimes very educational

</compliment>

Golf carts, gas and electric are very efficient for carrying a lot of weight, not so much for a light package. I don't see how you can carry what you propose with less power.

in all honesty, i had forgotten about gas engine golf carts. my first job in life was recharging a fleet of elec-carts at a large golf course for the summer. the imprinting of that electric experience bred bad memory.

If you want to avoid car parts, there are many ultralight engines, many in cars. The question becomes how much weight and how much do you want to spend?

the weight is at the core of the original post, eh? and seat of my pants says about $1000 (plus using existing left over parts) + decoration. might add $500 if i get a new engine instead of used. $500-$800 buys a lot of new small engine.

Scat makes an aluminum V4 based on the Chevy V8. Very cheap for the weight and very compact. Mates to all gearboxes too, I think.
After the Scat, they start getting lighter and more expensive.
Turbine would be the lightest. There is an 8hp model.

see above. i think a Scat V4 would weigh in at about $35k, which for Burning Man seems a tad excessive, yet would be awful entertaining and look real purdy too. and a Scat to go 5mph? seems mechanically sacrilegious.

Is packaging a factor?

brain fart here. what do you mean by 'packaging'? for transport? as decoration when assembled?

Will you re-use the drivetrain or burn it all? Does noise matter? Vibration?

i will haul out all hardware. would really rather gift everything else, even if it means hauling it to Reno to find Habitat's local chapter. would like the silence of a electric solution, but expect lawnmower-level noise minus creative muffling (i.e. high stacks for intake and exhaust). figured to put the engine mount on rubber bushings and won't really know the vibration factor until i decide on the engine and fire the sucker up - under load.

Auto trans with fluid drive can help with the shock and stall load problem I mentioned. Some bike engines can produce more power than the engine can actually survive under constant load conditions.

agreed on both points. the fluid drive has me looking at old lawn tractors (old Wheel Horse's have nifty potentials), but i still fear the weight and haul out. and the only bike engines i really have access too are for vintage dirt bikes, and they simply won't translate as hoped; and almost all demand 2-cycle mix. and none of the engines i have would tolerate the constant/level RPM.

i need to learn a lot more about transmissions and differentials... sigh...

.

gyre · Post by **gyre** » Thu Sep 18, 2008 11:15 am

Thanks. Very poetic.
I don't think I've ever heard that turn of phrase before.

By weight, I mean the weight of the drivetrain.
By packaging, I mean how it will all fit together.
Electric has huge advantages in this regard.
Even a small gas engine can use a lot of room for an adequate muffler system and intake.

Do I understand you won't be re-using the drivetrain in the future at all?

SCAT
When I priced them it was about $2,000 for the essential parts.
Keep in mind that only block, heads and crank are special.
It's just like the Drysdale V8 in this regard.
The V4 has been sold to a bike company and I don't know if they will sell raw engines anymore.
Phone is 858/650-0000.
There are many second hand though.
Ford did the same thing with their V6 based on the 289 engine.
All pistons, rods and valves work from the V8.

Well built aluminum engines tend to be made for power, so not as small as you propose.
Smaller ones tend to be less sophisticated and so not as light as they could be.
There are very good small engines but they tend to be special use and expensive.
The 4 wheelers that are built to do tractor duty may be as close as you can get in mass production, in engine type.
As people have mentioned, lawn tractors may work geared properly.

Of course, if you only want this to last one burn, you have some strange options.
I hope you'll pass it on to someone else when you're done.

On alternators, they create a load relative to the demand on them.
Other than weight, I think the bigger ones, especially the ambulance type, are the most efficient.

motskyroonmatick · Post by **motskyroonmatick** » Thu Sep 18, 2008 11:30 am

In '06 I spent hours trying to help a guy secure his Rubber mounted go cart engine so that the chain would not come off every 200'. I helped the situation but the chain still came off quite reliably.
I would suggest making the motor mount rigid and connected by bearings or whatever to the rear axle. If you are going with a chain drive. Then the rear suspension could absorb some of the vibration and the actual motor mount could be isolated by rubber bushings mounted between it and the superstructure of your mutant.
The most important thing with a chain drive is dead on alignment that does not allow the engine to torque sideways throwing the chain when throttle is applied.
I'd go with a larger chain like a motorcycle chain for the strength and it is just way harder to throw a bigger chain.

gyre · Post by **gyre** » Thu Sep 18, 2008 2:23 pm

There is a car out there powered by a small bike on a swing arm.
Probably 250 cc or so.
It is traction limited which avoids stress on the drivetrain.
It's acceleration is vague and so is the braking.
But it does work.
It's use is integral to this particular car and I don't know how practical it is to use on something else.
It might be just the thing for a quick build.
Doing this requires that the bike not be supporting weight.

falk · Post by **falk** » Thu Sep 18, 2008 4:19 pm

gyre wrote:For charging, hook into a big grid and chip in on the costs.

That's actually a pretty good idea. Maybe with one of those lightweight Honda generators as emergency backup if I get stranded. That's how the Daisy Big Wheel works, IIRC.

gyre · Post by **gyre** » Thu Sep 18, 2008 4:28 pm

Falk, what is your avatar?

gyre · Post by **gyre** » Thu Sep 18, 2008 4:32 pm

motskyroonmatick, what do you think of toothed belt drive?
I've been thinking of using that.
Would an idler help with a chain?
Or guides?

motskyroonmatick · Post by **motskyroonmatick** » Thu Sep 18, 2008 6:07 pm

I have no hands on experience with toothed belt drives but I know they are used on some motorcycles in place of a chain. No maintenance and little noise. I think it would work very well unless large amounts of torque were applied to it at startup. I think it might handle high rpm's better than a chain and emit much less mechanical noise. Heat fatigue could be an issue at high rpm's.
If chain systems are aligned correctly they should not need idlers unless the length between sprockets is really long or it impossible to tension the chain without one. There are tensioning idlers that are spring loaded that hold the slack side of the chain at a constant tension. Chain guides can be useful especially on the slack side of a chain. These are usually made out of teflon but I have seen ones made of oak before. They have rounded ends and a small lengthwise indentation for the chain.
The go cart I speak of was a real botch job and there was nothing short of tearing it apart and rebuilding the entire engine mount to solve the problem. Every time the throttle was applied the engine would deflect to the side and the chain would ride up on one of the teeth of the centrifical clutch sprocket and pop off. The chain was only slightly larger than a bike chain. The cart was geared to go about 35mph. The whole thing was a mess and basically unsuitable for the playa.

I think the avatar is a Tee shirt painting factory. Lift up, insert shirt, spray paint the man figure and remove. If that is what it is I loved seeing it this year as I have a real vivid memory of it my first year.

gyre · Post by **gyre** » Thu Sep 18, 2008 6:23 pm

I've used timing belts for years at a steady 10,000 rpm shift point.
Always check the idler bearings and the teeth on the pulleys.
When they round off, the belt will slip.
I never had a belt fail, except once with oil on the belt from a leak.

I think chains can be more reliable, but the good chains are quite expensive, power hungry and vulnerable.

motskyroonmatick · Post by **motskyroonmatick** » Thu Sep 18, 2008 6:33 pm

I agree. Belts are also easier to replace IMHO.

MikeVDS · Post by **MikeVDS** » Thu Sep 18, 2008 6:36 pm

I've had better luck with belts than chains as well.

falk · Post by **falk** » Thu Sep 18, 2008 7:11 pm

gyre wrote:Falk, what is your avatar?

Central fountain from my 2005 project: http://www.efalk.org/OasisDome/

gyre · Post by **gyre** » Fri Sep 19, 2008 1:46 am

Thanks.
That must have been amazing during such a dry year.

falk · Post by **falk** » Fri Sep 19, 2008 11:58 am

gyre wrote:That must have been amazing during such a dry year.

Aren't they all dry? But yes, it was very nice. Cool and moist. Temperature was typically 20 degrees cooler. There's a very small possibility it will come back in 2009.

falk · Post by **falk** » Fri Sep 19, 2008 12:00 pm

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"?