# Rotational house, motor (desperately need help)

1. Aug 13, 2008

### alexxan

1. The problem statement, all variables and given/known data
Dear forum users, I have big problem with motor, I don't have any Idea how I can make it. And maybe someone has an idea about this. I'm making rotational house for my finla project, finished with everything, only motor neede to rotate it. My house is 40tonns weight, and need to rotate for 220degrees in 12 hours. I want to make it as something like that:

and want to put it in that location, that rotational wheel will rotate and move house.

I found out that the total distance that it shound reach is 21.79m
Time = 12 hours

And I dont know what kind of motor should I chose to reach this goal, or where I can find some similar solutions?
I will really appreciate you help. Please, I desperately need you help. Also house is supported my wheels and central bearing. I don't know then what king of motor can do it. Also I calculated the speed and it sould me 0.03026 m/ min.

2. Relevant equations

3. The attempt at a solution

Last edited: Aug 13, 2008
2. Aug 13, 2008

### mshinavar

disneyland california has a rotating building, in large excess of 40 tons. maybe google that. i believe its called the imaginarium or something along those lines.

perhaps take the weight load with wheels (80,000 lbs is no problems for pneumatic tires, or even solid rubber tires), then use the central bearing only to control rotation, and not weight load. you could use wheel bearings even for that. bearings dont usually like loading in their axis of rotation direction

just copy that picture you provided. solid rubber wheels. and probably a high torque electric motor chain driving a drive wheel

3. Aug 13, 2008

### Topher925

Your going to need some serious gear reduction. Theres a lot of motors out there that will do the job. First look at your power requirement. Then what kind of motor you want to use (DC/AC, induction, PM) and then see if its readily available. I suggest looking at places that sell boat hoists. Big time reduction and powerful and reliable motors.

4. Aug 13, 2008

### mgb_phys

If you can get the track properly flat and level you will be surprised how little motor power you need, even with solid rubber tires running on steel rails. My guess would be 1/2hp would do, you can always double up with another motor on the other side.

Even with a gearbox it's going to be tricky to get a slow enough speed. A worm drive is the obvious solution but I don't know how much wear you would get.

Last edited: Aug 13, 2008
5. Aug 13, 2008

### Staff: Mentor

Thread moved to Mechanical Engineering, since it's a senior project.

6. Aug 13, 2008

### alexxan

thanks a lot for your answers, I heard from my supervisor that I need motor 1/2hp approx. (we have pretty rough relations with my supervisor, and he doesn't tell a lot at all)
But any way, for example my track supposed to be totally flat and level. But I have misunderstanding which motor can turn 40tonn house, if it has 1/2hp?

7. Aug 13, 2008

### mgb_phys

Rememebr once it is rotating you only need power to overcome friction, the mass of the moving object doesn't matter. As extra credit you could work out how much rotational energy an object rotating that slowly stores.

Large astronomical telescopes have very smooth bearings and can be pushed around by your hand in spite of weight 100s of tons.

8. Aug 13, 2008

### Staff: Mentor

Gearing is the key - it lowers the rpm and raises the torque. You'll want to do some calculations on that. Take a motor with a given rpm, take your wheels, calculate how fast the wheels have to spin to get your house to turn at the rate you want and divide one from the other. Boom - that's your total gear ratio. Then multiply that by the motor's torque and you get the torque delivered to the wheel.

Horsepower is torque (in foot-lb) * rpm/5252

9. Aug 17, 2008

### chayced

Just my 2c, but the motor itself will have to be over-sized. Sure all it deals with during steady state operation is the friction of the house itself, but when it starts it's going to have a lot of load on it and no RPM. Perhaps having some sort of clutch would help. Since this is just pencil and paper engineering not important, but in the real world motors do burn out.

Also research on rotating stages use in theater might help.

10. Aug 18, 2008

### FredGarvin

I was going to make this same point when I saw the OP. The thing you need to account for is a large power requirement when starting from a dead stop. You have to overcome all of the inertial and frictional forces and it will be more than your steady state value. I guarantee that. I have been burned by this in the past.

I'll look for the links, but Baldor Motors has some good white papers on their site for the proper sizing of motors to also include things like motor controllers. You get into whether you need constant torque or constant power, etc...

11. Aug 18, 2008

### Mech_Engineer

Yup, when you first start the motor up it will essentially be a short and one of two things will happen, you'll break something or you'll blow fuses. I would recommend coupling the motor to the house's drive train with some sort of hydraulic or viscous coupling, so that even when the house is not moving and the motor starts up the motor will still be able to rotate, and slowly add rotational energy to the house.

12. Aug 18, 2008

### RonL

http://www.esillc.cc/CAPSTANS .htm

Something along this line, using a system as simple as a proper sized rope, spliced into an endless loop. A single or double loop around a ring at the outer diameter of the house, and 3 or 4 loops around the capstan. A idler tension pulley to keep things snug, and a simple router type speed controller to regulate speed from 0-to max.

Building your own unit should be very simple and inexpensive.

Ron

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