Let's make the MADPHUC in Seattle!

[Pop_Tart]

Hello There!

I have created a Spark submission with all of the details. When it is approved, it will be located here: http://spark.burningman.com/ad-category ... -vehicles/. If you are interested with lending a hand in the design, fabrication, or vehicularization of the MADPHUC, then contact me via Spark or a Private Message and I will bring you on board.

I plan to use this thread as my build log, recording my weekly progress towards the design and fabrication of the Mal-mArt Deep Playa Hammock Utility Car, the MADPHUC.

Note: I came up with the vague concept for this vehicle a couple of years ago, and it has been bouncing around in my head and morphing for quite a while now. In the last two weeks I finally settled on a design concept and have been sketching out plans. So technically, this is just Day 1 of keeping a logbook of records.

Design Stage, Day 1:

My work has a tool that we use to inspect a large weldment. The tool is a welded steel 'wagon wheel' and is the basis for my design. Here is what I have so far.


2012-12-10_15-18-16_428 by JDisaPopTart, on Flickr


MADPHUC 2_1 by JDisaPopTart, on Flickr


Madphuc_Colorful by JDisaPopTart, on Flickr

My next steps are to make a rough SketchUp of the A-Frame support structure and to start working on the loads calculations to ensure this thing is built strong enough that it won't collapse and kill anyone.

Cheers,
PopTart
http://about.me/jonathanandersen

[trilobyte]

You may also want to take a look at AutoDesk's free 123D apps. Similar to sketchup in a number of ways, but better apps (desktop and mobile) and files can interchange with bigger 3D apps and 3D printing services should that ever be something you're interested in.

Good luck with the project!

[Pop_Tart]

Madphuc Journal Entry #2 - Material Selection, Statics, & Dynamics

The Design Process Continues. The whole thing is being designed to be as portable and modular as possible.

Complete:

Wagon Wheel Arm Lengths sized to accommodate hammock droop at max capacity
Wagon Wheel Arm Material set as 4" x 4" x .25" tube stock
Central Axis sized to accommodate length of hammock + connectors & caribiners
Central Axis Material set as schedule 80 size 3 steel pipe with weld on fittings on either end
Connectors & caribiners selected to accommodate max load conditions

Next Steps

Static and Dynamic calculations in work to determine if material thicknesses chosen are sufficient or too much. When complete, the weakest link in this whole machine will be the hammocks themselves. I'd rather have one of them split open and dump somebody out than anything metallic snap and people die. Safety 3rd, yes. However, Death and Dismemberment will not be 1st and 2nd.

Design Options:

1. Mount this contraption to the back of a flat bed truck. Drive the truck to BM, assemble the pieces together on site, and drive off into the dust, picking up random hammock riders in need of a good swing.

or

2. Make this contraption its own standalone vehicle. Tow it down to BM, assemble the pieces together on site, and drive off into the dust, picking up random hammock riders in need of a good swing.

Not sure which would be easier or more cost effective. Will continue to evaluate as I go.

[MacGlenver]

Awesome plan. I will ride the hell out of some hammocks. Maybe a padded floor just in case of a fall

PS - I could see someone's arm/head getting chopped off where the spokes of the wagon wheel cross the upright support if the thing's turning. Maybe put some plexiglass wedges (or whatever) between the spokes so it's actually a complete circle (and, thus, someone couldnt get their arm in there).

Another design consideration is keeping the wheels in sync with eachother so that one side of the hammock isnt at the top while the other side is at the bottom.... Prolly need a couple solid connection points between the arms (or some kinda gear system, but that'd get complicated i imagine).

[Elliot]

I like it.

You note in one of the drawings that the hammock pivot points will need to rotate well. I would consider going straight to large and very smooth bearings, since the hammocks will have little resistance to being twisted and the load on the bearings will be high. Just mounting-hardware that can be rotated will not likely serve.

On the other hand, the "wagon wheel arms" of 4" x 4" x .250"-wall may not need such a thick wall. Most of the strength is in the four inches. As you also say, you may be able to reduce this, perhaps to .120" (roughly 1/8"). And .250 wall would be awful heavy. You are thinking right to have a qualified engineer go thru this, and I look forward to a ride in it.

[graidawg]

ok this is damn cool. I hope it works out, perhaps a little shade over the top if you are going out in the daytime? i does get damn hot

[ygmir]

great idea!!
I'm wondering what the "max load" per person you calculate is?
I ask, because the "normal" 150 lbs calc. leaves a lot of us out. me, by 90 lbs (well, hopefully less by then, hahah). Not that I'd ask anything be done specifically for me, but I know lots of folks are over 150, and know that number is bandied about as an "average".

one might consider a ring, around the outside, or near the outside, of the hammock poles, for added strength and stability. a person, hanging that far out on just the central mount, is a lot of leverage. a simple band of flat bar (let alone angle or tube) would add a lot of strength and stability, end to end, like a wagon wheel.

Just some thoughts.
good luck and please keep us posted!!
PS: if you need some machine parts made, I have a metal lathe and milling machines.

[AbundantChoice]

great idea!! one might consider a ring, around the outside, or near the outside, of the hammock poles, for added strength and stability. a person, hanging that far out on just the central mount, is a lot of leverage. a simple band of flat bar (let alone angle or tube) would add a lot of strength and stability, end to end, like a wagon wheel.

yeah, a wagon-wheel design would add a decent amount of structural integrity to it. Especially because moving / swaying hammocks aren't really a static load, even if it's moving slowly. That would also make it really easy to "fill in" the 'pie pieces' of the wheel with fabric or whatever to cover the safety issue brought up above.

[Tiahaar]

MADPHUC 2_1 by JDisaPopTart, on Flickr

Love this! You tempted me to play with some load numbers so I did. The uprights have a high stress point where they attach to the deck and are pulled together by a sizeable force, the deck will want to bow if not sufficiently stiff, and its all completely doable of course. Though adding the blue bar at the central axis will help brace both uprights I like the open design without it.

[trilobyte]

I'd recommend setting your max load at something that's generous for two adults. Hammocks get that way sometimes, and designing it for that kind of overhead means you wouldn't need to be chasing couples or larger scale individuals away. I'm guessing a decent square tube steel with a decent weld should be able to support that easily enough...

[Pop_Tart]

I'm going with a 500 lb load per hammock. Eno DoubleNest Hammocks are rated to 400 lb, but I've had more weight than that in mine. Working on the math right now for both static conditions and some 'worst case' dynamic load situations (vehicle is moving 5mph while hammock is rotating with an un-balanced load, at max capacity, while people are bouncing around a bit from road bumps (or getting frisky]).

Thanks for the feedback everyone! Your ideas are getting rolled into the design as I go. More updates to come!


Analysis by JDisaPopTart, on Flickr


Parts_List by JDisaPopTart, on Flickr

[Pop_Tart]

Tiahaar - Your quick analysis is pretty much in line with how I am doing the math. My first quick pass showed a large moment-arm and tension forces at the axis too, so I immediately added a central shaft between the two wagon wheels. Without them it would be the one nut on the end of the axles holding the wheels to the rest of the structure. Plus, with a center shaft, I can keep the rotation of the two wagon wheels in lock step with a single motor. Lastly, the standard flange welded on to the end of the pipe fits perfectly with the bolt pattern of the hub, which should greatly help with the module build of the unit.

MacGlenver, Ygmir, & AbundantChoice - I'm definitely looking into braces and stay out barriers from spoke to spoke. When the wheel is rotated with the arms sticking straight out right and left, there is a pretty big moment arm there (especially with any dynamic forces applied from motion). Once the loads math is complete, I'll pick out material shape and size. Definitely a padded floor of some kind. Maybe some astroturf too.

graidawg - I'm thinking the shade will be part of the A-Frame type support structure that the wagon wheels will be mounted to. Stay tuned for some concepts.

Elliot - I'm considering either the 2932T23 Easy Swivel Ring from McMaster-Carr or a Fusion Brand Aerialist Swivel. Going to have to get one of each, cover them with playa dust (plenty of that laying around the house) and see which one binds up the least (or keep searching for a different option). Might also add a tall aerialist hoist hanging off the back for either performances or a hanging hammock chair.

[ygmir]

y'know a trailer axle/hub (even brake) assembly might do pretty well:
you'd have a large hub face with a bolt pattern, for the "wagon wheels" (heavy plate, arms welded to it, then it bolted to the drum/hub), bearings and such, rated for loads (get the axle rated for what you want), central tube already in place, and even a electric brake, if for some reason you needed to hold it from rotating.

[Pop_Tart]

I've been looking down that route a bit. The hubs & shafts from trailer parts USA are perfect for the center of the wagon wheel, but none of the axle tubes are long enough to combine the two wheels.

[Pop_Tart]

I hadn't thought of attaching a breaking assembly. That is a really good idea. I don't want to have to reach a hand into the works as the primary way to brake the rotation (as that will likely break a hand). Plus if someone starts to get sick or want off, it would be handy to stop it remotely and quickly.

[ygmir]

you can get axles up to 102" outside hub face as standard. and they're easy to extend, especially if round or square tubing.
Fishplate, and you can go as wide as necessary

[Captain Goddammit]

Electric trailer brakes don't work well to hold a stationary wheel in place, they use the rotational force of the brake drums to apply the brake shoes and I think they'd generally suck for this application.
I think it would be slicker yet to cut the spindle mounts off of the rear trailing axle of a front-wheel-drive small car and weld them onto whatever square-tube, plate, or surface your design wants. That was how I made the front axle of my mutant vehicle.
Besides the fact that you can probably scrounge it up free, the big advantage is it will have a cable-operated parking brake setup that you can use to slow, stop, and hold the "wagon wheels". You can mount up a hand-operated parking brake lever, probably sourced from the same junk car that donates the spindles, backing plates, and brake drums.

[ygmir]

good call CGD!! I'd say el. brakes would work, but not hold well. they'd stop something, but I wonder about hold. Didn't think of that.
yeah, cable "E brake", or even a hydraulic with a MC on a lever.

[Go2]

If you rotated the assembly 90 degrees (so the wagon wheel axle and ground wheel axles are parallel), you could use a gear & chain system from one axle to control the rotation of the wheels - if the vehicle's moving, the wagon wheels are rotating. If it's not moving, they're stopped. Put the motor and brake on that axle, and you've got a safe way to get in and out. Let the other axle wheels rotate independently, and it should still steer ok. This wouldn't work if you had to tow it assembled (~9' wide vehicle), but would be fine for on-site assembly.

[Captain Goddammit]

Changing the whole design by turning the rotisserie 90 degrees isn't necessary, for road-driven rotation you could simply use a rear axle with differential from a small Japanese truck and drive the rotisserie off the U-joint (replaced with a sprocket).