Looking to get some help with a vehicle project... resources

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Looking to get some help with a vehicle project... resources

Postby caveatlector » Tue Mar 02, 2010 2:29 pm

Hi all! I'm preparing for my first burn, and was wondering if there were building resources for those of us who are thinking about making a vehicle or small installation.

I need someone to look at my idea essentially and give me feedback about potential issues. I'm aware of the dusty nature of the playa, as well as the unrelenting dryness and heat at times, and I've designed accordingly.

Any recommendations would be greatly appreciated!
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Postby Captain Goddammit » Tue Mar 02, 2010 6:09 pm

There are several of us who have built playa vehicles on here... show us what you've got in mind and we'll add playa-wise input!
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Postby LeChatNoir » Tue Mar 02, 2010 6:16 pm

Hi caveatlector,

Welcome to eplaya. Taking on a Mutant vehicle or art project for your first burn is ambitious, but certainly not un-doable. I always advise people to come their first year and scope it out. It’s such a sensory overload at times, that it can’t really be described and after you’ve been you may find ways that you’d want to change your project‘s intial design to better suit.

That being said, there are numerous tinkerers and builders here. Starting a thread about your project will get you lots of good advice, plus it can provide you and others a lot of fun… sort of prime you for the whole interactive Burning Man experience. And the more you do you homework and throw yourself into your project, the better your response will be from those here who also are driven to create.

Here’s a good example of a thread started to document and trouble shoot a project:

the Aluminipede Thread

And of course, you’re welcome to come over to The Contraption thread and lurk, read, chime in… whatever you're comfortable with.

Also, Mutant Vehicles are much more than just bringing it and driving around. You must go through the serious of hoops with the Department of Mutant Vehicles to get an invite, then you must pass up to three different inspections (Day, Night, and Flame Effects) before you can operate your MV on the playa.

Find DMV info Here.

An art piece can be as simple as bringing it and setting it up in your camp. I’m pretty sure that if you want to place your art out on the open playa, then you must jump through some similar hoops with the Artery to get it placed. I’ve seen people do stuff without this process though, but less often. At the very least, make sure it‘s well lit up at night, all night, every night so nobody crashes into it on a bike.

And above all else, before starting anything, read the First-Timer’s guide over and over again.

Welcome aboard!! Tell us about your project ideas.
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Postby AntiM » Tue Mar 02, 2010 11:07 pm

There are a few hoops for a placed piece on the playa, and then you're on the map. Not too bad, I managed it. But really, anyone can set up anything out there. Yes, it has to be secured from the wind and lit up at night, and not be in someone else's spot. There are markers if you know what to look for.
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Postby caveatlector » Wed Mar 03, 2010 12:09 am

I'm so pleased to see so many useful tips and people willing to help. I know I'm biting off more than I can chew, so I am not really holding my breath about getting the vehicle done in time this year-- but I like the idea of the project so in the very least I'd like to get started.

The idea sort of liooks like this:

Image



I want a vehicle that you have to carve with to turn, very much like a real dog sled. I've got a friend who's got an engineering background looking at the various hub motors I could use for this instance, but if you want to look at what I'm considering specs can be found at http://www.goldenmotor.com in the hub motor section.

When finished, depending on cost, I'd like one or two LED / ELwire sled dogs suspended up front as well (again, not sure how to affect that).

Thanks for your attention! I'll be going over the information that LeChatNoir provided to see what I'm forgetting / missing / competely overstepping.
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Postby Captain Goddammit » Wed Mar 03, 2010 9:19 am

Wow, love it!
One comment, the small wheels... aesthetically I know you'd want them small as possible so as not to be prominent cuz dogsleds aren't supposed to be wheeled vehicles, but for practical reasons you might wanna make 'em a bit bigger. Some years the playa is smooth and hard and presents no problem, some recent years it was hard to even ride a bike.It was very soft and choppy.
Maybe you can find a slick way to use bigger ones and hide them, under "luggage" or something.
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Postby caveatlector » Wed Mar 03, 2010 10:07 am

Captain Goddammit:

I'm sort of stuck on the wheels at the back, I think, if I want to keep with the idea of lean-and-turn-- unless I decide to go insane and tool my own mondo-sized trucks that can handle a larger wheel set (which isn't a terrible idea but not something I can do for this year).

Locally, I can pick up a pair of these:

Image

They're 113MM wheels-- about 5". I'm not sure if I could find any larger.

I've assumed that since I'm using front wheel drive with a pretty large wheel, that the back tire size is less important, but that's using a poorly educated set of engineering instincts.

Things that my picture doesn't show are the battery packs for the Elwire "dog" silhouette on the front as well. Those packs will be the key to keeping the weight forward so I have actual traction. I might need to sandbag the front further, but I"ll play that by ear.

Actually, I'm not even sure if using an electric motor is such a good idea anyhow since I'm really unsure how I'm going to charge the batteries once I'm there-- but I really don't know much about internal combustion engines (I'm a nerd, not a grease monkey).

Thanks for the input! Any further advice would be greatly appreciated.
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Postby LeChatNoir » Wed Mar 03, 2010 10:25 am

Smaller wheels mean a higher coefficient of drag. On hard pack playa I suspect it’d not be a problem, but if it’s soft and crunchy, it could be. And if there are periodic dunes and sand traps, like in 08, they could stop you cold. Though that would likely be the case even with larger wheels. .If these are pneumatic tires, maybe keep the pressure on the high side

Adding suspension of some sort under the trailing wheels could make your ride more comfortable and less stress on your vehicle. The streets can get pretty rutted in places, depending on the playa conditions.

This sort of reminds me of a windsurfing set up. Anybody here on the board done that on the playa?
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Postby LeChatNoir » Wed Mar 03, 2010 10:31 am

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Postby Captain Goddammit » Wed Mar 03, 2010 11:13 am

I noticed the strategically-placed batteries, for ballast and shorter cable runs, your excellent diagram did show that. Smart figurin'! Unfortunately, playa conditions lately have been lot worse than you might be expecting. After riders are aboard, I think you're still gonna be tail-heavy, so it might be worth considering rear-wheel-drive
I have a skateboard with wheels about 5 or 6 inches in diameter I used to tow as a "waterskier" behind my Land Yacht. Whenever the rider would encounter the choppy playa "waves" he'd invariably fall off. In '08 people were pushing their bikes through the playa, and that was with 26" wheels.

There's been much discussion about electric vs. gas power for playa mutant vehicles. The general consensus among playa-vehicle makers leans toward gas engines as the most practical, mostly because battery technology isn't where it needs to be to store enough energy, plus long recharge times. But there are always other factors; if you're lost with engines but comfortable and "in your element" with electric power, maybe in your case electric is the way to go. You're gonna need a generator to charge with though. That's the big Catch-22 with electric playa vehicles - you're gonna have to run a gas engine to make the electricity anyway... unless you have a LOT of big solar panels. An alternative if you have a small and efficient car (or lots of gas!), and a nice QUIET generator just isn't in the budget, is to run some jumper cables from your car to your sled and run the motor while it charges. Remember, most car alternators produce nowhere near their rated output at idle speed, but you can speed up your charge times by using heavy-gauge jumper cables, and using two or three sets at the same time. That carries a lot more current - try it next time you're trying to jump-start a vehicle who's battery is too dead to crank even with cables hooked up; old trick from my AAA tow-truck driving days.


The EL-wire sled dogs out front is a terrific plan, it'll look awesome at night. That concept been done with great success. Basically you make up a thin frame and lay out the design on it, visible on both sides, and the really good ones use a sequencer and a few EL-wire layouts to give the legs (or whole dogs) motion. You seem like the kind of guy who could make that happen.
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Postby caveatlector » Wed Mar 03, 2010 12:14 pm

Thank you, LeChatNoir, I think I might use these pneumatic tires. The ones I've been considering using are solid plastic and might simply dig into the dirt.

Captain Goddammit: Do the playa conditions vary wildly from year to year, or are they degrading further with each BM? Should I be considering more of a tank-track drive for a 2014 vehicle? :wink:

I think if I can make the vehicle work, I'll probably stick with electric and rent a generator-- the electricity could come in handy for other things such as my kettle / lights / stereo system -- and I can keep moving and greased bits to a strict minimum. I fear what the dust can do to a gas engine.

Oh, if you have access to a sled dog profile, awesome. You'd be surprised how difficult it is to find one using Google Image Search.
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Postby AntiM » Wed Mar 03, 2010 12:20 pm

The playa surface refreshes each year, it does cover with water, the freeze and thaw reset conditions. I know that's over-simplified, you geeks! If there is not enough winter/spring moisture, the surface will be soft and rough.
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Postby rodiponer » Wed Mar 03, 2010 2:39 pm

This is cool. I like your diagram, idea, and details.

In case the playa is really soft this year, I think you should design the rear pedestal to be strong enough that you can use it to push the vehicle when it gets stuck. Real sleds do this anyways. Even better is to have a rail on the sides that the passengers can use as hand holds to help push.

I would make the rear wheels at least as big as the tires on a kids bike. I think the vehicle will get more stuck if the small back wheels get buried. I think you could hide them in the design of the vehicle, maybe inside side rails or luggage. I don't think the outrigger tires need to be larger, since they will rarely touch the ground.

I had a hub motor on the front wheel of my mountain bike, which I used to drag myself and my disabled daughter in her kiddie bike trailer. I really think that front wheel drive is the way to go. The spinning front wheel pulled us through the soft sand much more effectively than when I was pedaling the back wheel. I don't know why this is. It did lose traction sometimes and just spin, but it still propelled us pretty well.

The Captain has a whole lot more experience at )*( and with mutant vehicles than I do, but I disagree with him about electric motors. I think you just have to size the batteries appropriately and know how to maintain them. I think the negative impression people have of electric drive may be from throwing an electric golf cart in storage for 11 months, letting the batteries completely discharge, dry out, sulfate, or whatever, and then trying to resurrect them the week before or while at Burning Man. In that circumstance a gasoline engine would be much more reliable, since people understand them better-- clean the carburetor if it's clogged up from being in storage for a year, and you are good to go.
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Postby Ugly Dougly » Wed Mar 03, 2010 3:13 pm

I think we are getting a lot of H2O this year.
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Postby LeChatNoir » Wed Mar 03, 2010 7:59 pm

Wire frame sled dogs in two to three “snap-shotâ€
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Postby capjbadger » Tue Mar 09, 2010 2:57 am

With the overall size of the vehicle, I'm a little surprised no one has suggested cutting out the engine/motor completely and making it pedal powered. No DMV hoops to jump through and that frees up your battery for just sounds and lights and EL wire.

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Postby Captain Goddammit » Tue Mar 09, 2010 7:57 am

Well next time you're on my boat I'll hand you an oar!
No motor? Are you feeling OK? Still feeling effects from that night at my camp in '08 when we were drinking shots of tequila and eating pickles?
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Postby LeChatNoir » Tue Mar 09, 2010 10:12 am

capjbadger wrote:With the overall size of the vehicle, I'm a little surprised no one has suggested cutting out the engine/motor completely and making it pedal powered. No DMV hoops to jump through and that frees up your battery for just sounds and lights and EL wire.

-Badger


You're right! The first year for us we had no DMV issues since the vehicle was human powered. However, with the addition of passengers to the dog sled, it could get tough quickly unless they somehow help pedal.
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Postby gyre » Wed Mar 10, 2010 12:20 am

How is a dogsled steered by leaning?

I thought dogsleds were steered by persuading dogs to go in a particular direction, and then dragging the sled along.
The leaning is to keep the sled from tipping over.
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Postby caveatlector » Wed Mar 10, 2010 10:57 am

How is a dogsled steered by leaning?


It's been about an eternity since I've driven one, but what I can recall: A dogsled is actually controlled by a combination of leaning and the dogs. A good track helps as well on keeping the sled on target.

When you lean on a dogsled, you're putting torque on the frame, which puts pressure on the sled runners-- sort of like turning when you ski. The sled is basicly kept from skidding all over the place by doing that.

Back on topic:

I had another builder suggest that I make the whole thing rear-wheel driven, saying that my weight will be too unevenly spaced to actually get traction.

That makes sense, but now I'll have to rethink the whole design. Anyone got any thoughts on that? Would adding another set of giant trucks on the front and just a single powered wheel on the back work?

Is it back to the drawing board for me?
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Postby Captain Goddammit » Wed Mar 10, 2010 11:45 am

You know, the single (driven) rear wheel idea might be worth investigating just because you could conceal it really well. I have the two front wheels of my boat spaced only about a foot apart, it's almost a tricycle, just because I was able to keep them tucked inside the hull that way.
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Postby rodiponer » Wed Mar 10, 2010 12:21 pm

Well, I think the front wheel will have plenty of weight on it. The two batteries should weigh something like 60 to 120 pounds, and will be right over the wheel. The rear wheels are on the end of the sled, so any weight in the sled will contribute to pushing down on the front wheel. It would be different if the rear axles were not on the aft end of the sled, since then any weight behind the rear axle would contribute to pivoting the front wheel up.

Here, it only takes a second to do the math. Just calculate the center of gravity, which you can do by hand or in a spreadsheet. Have X=0 at the front wheels axle, then for everything you can think of, add up the weight of the thing times the distance from X=0, like so:

Batteries (6", 100 pounds) = 600 lb/inches
Throttle controller (12", 1 pound) = 12 lb/inches
10' aluminum tubes, 2" square, 0.125" wall, running fore and aft at 1.1 lbs/foot (60", 22 pounds) = 1320 lb/inches
170 pound guy 10' back (120", 170 pounds) = 20,400 lb/inches

Then add up all the moments: 600 + 12 + 1320 + 20400 = 22,332 lb/inches
Add up all the weights: 100+1+22+170 = 293 pounds
Then divide the moments by the weight to get the center of gravity: 76"

Let's say the two axles are 10'6" apart, or 126" apart. To get the total weight pushing down on the front axle, just divide the center of gravity by the distance between the two axles and subtract that from 1, so: 1 - 76/126 = 1 - 0.6 = 40% of the weight is on the front axle, or 40% of 293 pounds is 117 pounds.

Add a 170 pound person sitting in front of you, say 6' from the front, and the numbers become:
Moment: 32,640 lb/inches
Total weight: 463 lbs
CG: 70"
Weight on front axle: 45% of total weight, or 208 pounds

By comparison, my bike with a hub motor on the front wheel weights about 250 pounds with me on it (yes, I have pudge). I think a bike has more weight on the back wheel than on the front wheels, but to be simple and generous we can just say that 125 pounds was on the front wheel. This was enough downward force to generate traction for the motor to pull me and tow a 100 pound kid trailer around the playa. Though I did have to get off an push on the biggest soft spots.

OK, this looks more complicated than it is when you write it out. But it's very easy to add this all up and figure it out in a spreadsheet.

I still believe in the power of front wheel drive, especially with a large front wheel. It will spin and help climb over the sand snakes.

There are smaller hub motor wheels that you could also use for the rear wheels. For three wheel drive. That would be cool, too, and certainly helpful if you never want to push.

I think an important detail is that the rear wheels are large enough that you won't get buried up to the axles or frame of the sled. Maybe assume that the deepest the soft sand ever gets is 6 or 8", so the wheels should be at least 12 or 16" in diameter.

On more suggestion for your design-- have nice headlights that shine on the ground at least twenty feet ahead. At night it is hard to drive around the soft spots on the playa if you can't see them. So with the dinky little bike light I had I tended to get stuck much more often at night.
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Postby Captain Goddammit » Wed Mar 10, 2010 1:02 pm

Your formulas seem fine but I don't think your application of them is. If I'm interpreting the diagram and dogsled profile correctly, the operator will be at the extreme rear, not in the middle where his weight will transfer at all to the front wheels. I think it's gonna be real tail-heavy. Do you remember riding a Big Wheel as a kid? It was front-drive but tail heavy, and sucked on anything but flat hard ground. This dogsled is very similar in configuration. It will work as a front-drive rig, but I'm betting it has traction problems if we don't get a nice smooth hard playa this year.

A friend and I built my boat. We did it via the concept argument method... by the time we agreed on anything, we were pretty damn sure it was right!
The brake pedal mechanism was funny... I had one idea, he had another. We both successfully argued our idea's merits until I wanted to do it his way, and he wanted to do it mine. Then we had to argue back the other way!
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Postby Captain Goddammit » Wed Mar 10, 2010 1:17 pm

Actually after some further thought, maybe a combination of our schools of thought would be best.
How about front-drive, but move the front wheel back, maybe about mid-ship, for better weight transfer? The batteries could then be ahead of the drive wheel, gaining a big traction advantage, and you'd have the climbing-over-stuff advantage of front drive.
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Postby gyre » Wed Mar 10, 2010 1:34 pm

There is nothing magic about front wheel drive.
If you were pedaling, your bike was two wheel drive, not front wheel drive.
A bike powered through the rear wheel alone will out perform a front drive setup.


Weight and traction is what counts.
All wheels have a traction circle defining their limits.
This is why front wheel drive is the worst choice for an automobile.
There are other dynamic issues, as well.

I used to balance my (very obviously) rear drive roadster to just barely be able to get traction in the rear.
This gives maximum steering and braking.
Then I went out in the snow to torture front wheel drive owners.
Uphill was much, much worse of course.


Building for the playa, you can set your own goals.
Multiple small wheels have been used before.
Wide and smooth tires work best out there.

There have been a number of vehicles on the playa that steer by leaning.
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Postby Bounce530 » Wed Mar 10, 2010 2:30 pm

gyre wrote:There have been a number of vehicles on the playa that steer by leaning.


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Postby gyre » Wed Mar 10, 2010 2:55 pm

Check out Moebius for an interesting steering design.
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Postby capjbadger » Wed Mar 10, 2010 5:15 pm

Captain Goddammit wrote:Well next time you're on my boat I'll hand you an oar!
No motor? Are you feeling OK? Still feeling effects from that night at my camp in '08 when we were drinking shots of tequila and eating pickles?

Haha And your very drunk friend that couldn't get enough of the "pickle juice!" lol

BTW, I have real vacation time again, so I'll see you out there. :)
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Postby capjbadger » Wed Mar 10, 2010 5:25 pm

LeChatNoir wrote:
capjbadger wrote:With the overall size of the vehicle, I'm a little surprised no one has suggested cutting out the engine/motor completely and making it pedal powered. No DMV hoops to jump through and that frees up your battery for just sounds and lights and EL wire.

-Badger


You're right! The first year for us we had no DMV issues since the vehicle was human powered. However, with the addition of passengers to the dog sled, it could get tough quickly unless they somehow help pedal.

Well I was thinking of having the passengers pedal too to offset the additional weight.

As for the drive wheel placement, that's simple. put the drive wheel where the weight is. Looks like the back to me on this one. :)

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Postby rodiponer » Wed Mar 10, 2010 5:39 pm

Hi,
I think we should keep in mind that he's taking about a bicycle hub motor, maybe 1000 watts (~1 hp) of output. I haven't seen larger onees. I think the motor will run out of torque long before the front wheel runs out of traction with 200 pounds of weight on it. Moving to rear wheel drive with 600 pounds of weight won't do anything, it will still stall at the same place.

I agree that rear wheel drive is best for a bike. But I think front wheel drive has advantages for this vehicle in soft sand. On a bike, if the front wheel starts to get stuck you can shift your weight back and try to lift the front wheel out of the muck. He won't be able to do that with this design, so I think it's better for the front wheel to instead be driven so that it can climb and lift itself out and over the muck instead of staying buried and needing to be pushed through it.

But maybe I am wrong, and the rear wheels will then just get stuck in the ruts if they aren't driven.

Well, I just made up numbers to show how a spreadsheet would work, if he wanted to be very nerdy about it he could add up dozens of things, starting with the heaviest things until he feels like he has a good enough idea.

But even with more details, the math is that the batteries will always push down on the front axle no matter how much weight is in back. Something that is halfway between the front and rear will split it's weight evenly between the front and rear axle. The base frame's center of gravity will probably be halfway back, so half of it's weight will go to the front axle. So I think with the batteries and frame he'll easily hit over 200 pounds on the front axle without any passengers.

It's true, a driver who is standing 6" forward of the rear axle on a 10'6" sled (as in my rough example), nearly 95% of their weight will be on the rear axle, and only 5% on the front axle. So their 170 pounds will only add 9 pounds of down force on the front axle, but it doesn't decrease the amount of weight on the front axle.

If the front wheel is moved back, he should increase the ground clearance so that the bow of the sled doesn't dig into the ground when the front wheel goes into a trough.

Now if only I knew enough to calculate the difference in friction between ball bearings and plastic sleeve bearings for my mutant vehicle. I tried to estimate it with a 20 pound experiment, where there was no difference between the two bearings, but want to figure this out for 200 to 300 pounds. Maybe I need to mount this to a hammock swing and load the kids in. Or learn the math.
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rodiponer
 
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