Manually Operated Rotating Platform

Is this 'treehouse' to be life size (as opposed to a too-small to be occupied)?

If yes, my bigger concern before offering advice would be life safety.

If no, mount a (doll size) treehouse on top of... what?

Safety is always a concern however the primary purpose of this rotation is to simply change the position or direction the treehouse is facing. it will not be turning on an ongoing basis or for the purpose of being an "amusement ride". The axel with steering wheel is interesting but how would it turn while standing on the platform

"...but how would it turn while standing on the platform"

The red post extends through the rotating part and is attached to the stationary base. Pulling on the wheel drags your feet around, along with the rotating platform.

Your pic nailed what I was visualizing.

When I read your #3, this type of playground merry-go round came to mind.

Boys being boys, it may be wise to consider some type of speed governor. I am pretty sure that I, at age 7, would get a bunch of friends together and get that baby spinning as fast as I could!

I see what you are saying about the wheel and how it would work however I'm not sure that it would be very easy to move when you add walls and a roof to the mix..

I was thinking along the line of sort of basic gear or cog system that might be able to easily turn the platform from a pulley type mechanism.

Would it be correct to assume that this is outdoors?

How often will this rotation feature be used? Should it go round and round forever or will rotation be restricted to back and forth on less than a 360 degree arc?

Will the tree house be occupied during rotation? If so, will it be occupied by kids "boys will be boys" who will be jumping up and down and creating a lot of mechanical stress on the rotational devices (bearings, wheels, whatever).

Without knowing any answers to the questions above my only thought is to have a strong and safe platform under the floor of the tree house. Install something like a pipe flange to create a pivot point on the lower platform. Have either pipe or a 2'x4' constructed box to receive the pipe on the bottom of the upper platform (tree house floor). Install several fixed position casters on an arc to hold the weight of the tree house floor as it rotates and then sits stationary.

All safety issues are up to you. Above comments are conversation only. I certify that I have no qualifications whatsoever in the design area discussed in this posting. A very long time ago I was a young boy and therefore I tell you that all safety rules will be violated and if it is possible to pinch, trap or crush toys or body parts in the rotational mechanism then it will be done. When I was young dirt and blood were part of the day's fun. Now it is the source of lawyers income. If you proceed then do it with caution.

On the basis of of BruceFlorida's design, how about extending the fixed axle up through the rotating platform and mounting a steering wheel on top? Or alternatively some pulleys with a wheel or crank near the outer edge of the platform.

How big is your tree?

The tree will is actually being cut down so that the trunk will be left as a base for the treehouse. I will be building a platform on top of what will be a forked trunk. So the challenge is to be able to turn the treehouse through some manual method either while on the platform or through a pulley or cranking mechanism accessed from the ground .

How about using as the platform of your tree house a big "lazy Susan", similar to the big round tables used in chinese restaurants!

Two platforms separated by a "pipe" type bearing in the center with small wheels mounted around the edges such that they bring the top platform above the lower one.

Make the top platform a bit smaller than the bottom one and you can then have some poles on the lower one that you could "grab" and just pull yourself around to the new position. Having some sort of "locking device" for each position would be a good idea as well. Maybe a pipe that goes through both platforms and can be locked in with a padlock.

I see no need for elaborate mechanisms to turn it to a new position now and then...unless you do want to create a "ride"!

That sounds like a great idea. Even a fixed railing attatched to the lower platform could act as those poles that you mentioned to grab and pull yourself around.

Thanks for everyones input

Several years ago, in need of of a rotating hoist to move and pull tractor motors, I concreted a huge truck axle 3 foot under ground with a 4 " stem 8 foot high that would rotate 360 degrees. It hasn't budged after 30 years of use..May have to get rid of the tree or use it for a entry way..but load and safety would sure be cut to a minimum..Then as in the olden days we grew up, useing our heads, knowing thing bigger than we were could cause great pain.

can you please clear about the weight it will bear?

About ten years ago I needed to build a lazy susan roughly 6' in diameter for use in testing radio-frequency emissions and susceptibility. One requirement was that it have little or no metal in it, but it needed to be able to support several hundred pounds in addition to its own weight. I used MDF (Medium Density Fiberboard - was able to find two extra-wide pieces so didn't have to splice) and used a 1-1/2" radius router bit and a long trammel rod to rout grooves into each half for the upper and lower "races". I then placed 7 dozen ping-pong balls* in the lower groove, and set the other half on top. It has had two adult males sitting on it while being rotated, with no problem. A groove around the circular top piece has a rope making nearly two full turns, and the rope feeds in-&-out via plastic pulleys. The platform can be rotated from 10 or more feet away without disturbing the test. A band made of plastic strapping material wraps around the rope and keeps it in place; the ends are lightly spring-loaded. Rotation is entirely due to frictional contact with the bottom of the groove; no direct connnection. I left the lower support as a hexagon and let the corners serve as leg-mounting locations and for the pulleys. The legs are 4" plastic DWV pipe and flanges.

I put 4" plastic DWV (drain, waste, vent) pipe through central holes so that we can feed power and signal cables to the equipment, with plastic flanges. We limit rotation to about 720 degrees. Doing the same in metal and locking a cap to a pipe nipple extending below the supporting deck would prevent lifting or tilting the top piece; the flange could be bolted to the bottom of it with no access except by lifting the entire top (after removing the locked cap).

I intended to disassemble and varnish the grooves after checking functionality; as usual, it got pressed into service immediately and never did get the sealing coat - but it is still being used and working just fine. For outdoors, I'd think that two layers of 3/4 marine plywood, or a hexagon or octagon of treated lumber, would work for the raceways. Plastic balls are available in bulk from plastics supply houses as a floating cover for tanks of liquid, to reduce heat or evaporation loss. They'd hold more weight than you'll ever need.

*The lady at the sporting goods store wanted to know if I was running a ping-pong tournament, and I told her that, no, the balls would become part of a giant lazy susan; I'm not sure that she believed me!

If you were to get a complete rear axle from a junk yard, a workable rotator can be made fairly easily. Stand the axle on end, and fix the lower wheel studs to the stationary mounting base. Fit an old steering wheel to the place where the driveshaft used to bolt to. On the top axle, pass a long bolt through the backing plate right through the axle flange, and tighten. This will force the entire axle housing to rotate as one turns the steering wheel. Then a platform is built around the axle housing, attaching it where ever possible directly to the housing. Now the kids can stand on the platform and turn the steering wheel, forcing the platform to rotate.

While it may be too tall for use as on top of your tree stump, it will work well bolted securely to a concrete pad. The friction involved in the internal differential gears keeps the speeds and momentum to tolerable levels. Good luck.

A differential from a Corvette or..._Jaguar would be shorter but cost might be a factor. VW transaxel?

Good idea. Without the extra width of the standard axle, the finished project will be much lower. With some fabricating, could probably get a FWD differential to do it.

Bob thanks for that great idea. There are a couple of things you mentioned that I was unclear about but in general it sounds great. Why would the height of the tree trunk be a concern if the wheel stud is mounted to the fixed platform which would be firmly mounted to the top of the long trunk? I'm trying to get a coplete picture.

My concern is that the mounting of the wheel studs must NOT be unable to come loose, and that the floor of the platform is not close to ground hight, and will be able to spin. Are you comfortable the children and that arrangement? You know the children better than I do.