Automotive Window Motor for Power Bus Door?

Converted schoolbus, rear door

Currently if the bus is closed, I have to open the heavy rear door to get in.

Converted schoolbus, right front interior

I don’t have a good picture of just the door, but the rod going horizontally across from the handle in the center of the bus to the door (hidden behind the cabinet) mechanically holds the door closed (by design) when the handle is latched in the closed position. As long as the handle stays latched, you can’t open the main passenger door from the outside.

With my highly-skilled momentum technique, I can close the front door from the outside so I don’t have to walk around, open the rear door, walk through, close the front door, walk around, and reclose the rear door; but once done, I then have to do the hokey-pokey to get back in.

I’d really like to be able to lock the passenger door and have a way to get in from the outside. And unlike many other bus-RV converters, I really don’t want to replace the bus door with an RV door — I’m not out to hide the fact that the vehicle started life as a bus. Until I have good reason to feel otherwise, I’d like to keep the accordion-fold door.

I’d love to motorize the door and add electronic entry — although at least in the long term, I need to have a purely mechanical way to get in, as backup in case something goes wrong with the motor.

Automotive Power Window Motor

Automotive power window motor assembly

“Neighbor Dan” has a pile of removed auto parts in the corner of his shop, and a guy comes by occasionally to haul the pile to a scrapyard. Dan has offered me anything I want out of the pile, and he says he has three more of these power window motors that I haven’t found yet. I’ll keep digging.

I don’t know that this is the motor to use for my power door, but it bears consideration.

Automotive power window motor assembly, opened

It looks pretty obvious why it was replaced — the cable is all messed up and broken where it wraps around the spool.

Automotive power window motor

With the jammed-up cable spool taken care of, the output shaft spins at almost two rotations per second. That’s a little fast if I were going to attach it directly to the door-opening handle or use it to replace the handle altogether. If I were to do that, I might use pulse-width modulation (PWM) to slow it down.

The motor coil resistance is 1Ω or less, so the motor draws at least an amp and I’d need a pretty hefty FET to drive it. (A compensating factor is that the motor would normally have a pretty short duty cycle, so the FET wouldn’t have long to heat up.)

Alternatively, I could use the motor with the spool and cable (maybe one of the others isn’t as messed up) and use a larger pulley / spool on the handle end to “gear down” the rotational speed.

I’ve considered that I could remove the manual handle, do away with the connecting rod, and fabricate an entirely new means to close the door. But as it’s constructed now, the rod does double-duty closing the door and “locking” it shut once closed. If I did away with it, I’d have to recreate that functionality on my own.

I’m Open to Something Completely Different

If someone knows of a better way to lock and unlock a bus front door from the outside, or motorize an accordion-fold door, I’m all ears.

7 Responses to “Automotive Window Motor for Power Bus Door?”

  1. Dave says:

    Consider the options carefully. You don’t really want the door unexpectedly popping open while you’re driving the bus.

    Also, consider the force necessary to operate the handle/rod (and, consider what it would do to some fingers placed at an inappropriate spot!).

    Also, consider emergency egress in the event of an accident! You don’t
    want to wait several seconds for the door to open if the interior of the bus is on fire (I live not too many miles from the “Carrollton Bus Crash” site, and narrowly avoided being one of the emergency responders responding to that event.). :-(

    Also, since I’m thinking of that, you might want to check the location of the bus’s fuel tank, and ensure that it’s adequately protected in the event of a side impact crash. I seem to remember some recommended refits to gasoline powered buses to better protect the fuel tank.


  2. TLHarrell says:

    Many buses have a mechanical means to pop the handle out of it’s locked position, usually some sort of plunger button on the front of the bus. When pushed inward, it unlocks the handle mechanism. The door can then be forced open by hand. Generally the plunger would have a hole drilled through the shaft where it protrudes outside the bus shell where it can be secured by a standard combo or keyed lock. This mechanical system could also be actuated by a solenoid or your window motor as well while maintaining the ability to manually open it.

    If you’re not sure of how this relates, shoot me an email and I’ll sketch something out.

  3. neufeld says:

    Thomas, I’m leaning toward actually doing away with the traditional door-opening mechanism and refitting the door with a different kind of lock. I don’t have the details worked out yet, just some thoughts along those lines. The motivation is largely that doing anything with the existing mechanism is going to be somewhat Rube-Goldberg, that it occupies space and makes visual clutter at the front of the bus that it doesn’t need to, and that I don’t need to be able to open and close the passenger door while buckled in like a bus driver would.

    So although your comments about the plunger button aren’t the direction I’m leaning any more, they’re still appreciated and match what I’ve seen elsewhere.

  4. meagan says:

    hey, did you ever think about using a solenoid (these have been more popular in recent years for hot rods and custom cars that have shaved door handles) to pop open the door? youd have to use the remote dealy to open it, but maybe you could fashion some sort of emergency unlock on the inside for emergencies? theres prob tons of things that use solenoids that you could source from so you could save $$$. anyways, awesome bus!! someday i hope to get a school bus to convert and live in – thats the dream anyways. :)

  5. Matthew says:

    Whatever happened to this project? I am curios because I just recently bought a bus that uses a dc motor that looks damn near identical to your wind shield wiper motor. One of my concerns and disbelief is that this type of motor delivers enough torque (force) to push the door open…. considering gear ratio.

  6. neufeld says:

    Matthew, I’ve chosen not to pursue a motorized door opener, but I have no reason to believe it wouldn’t work. It’s a matter of gear ratio and torque — remember that a window motor like this will close a car window on your arm hard enough to hurt.

  7. Danika says:

    Don’t know if you’re still working on this project, but I am using a retired school bus to transport pets to spay-neuter surgery (Photos on website)
    I found out that there is what’s called a “vandal lock” that secures the front doors without motors or removing the original mechanism. It locks the doors and has a bar that attaches to the regular door opener. A company called TAC Bus Parts in Ohio sells them (about $50), if you have a Thomas or Bluebird. Unfortunately, I have a Carpenter, and I found your site while searching for someone who might know how to get one for my bus… Good luck on your project.

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