Replace door actuator with electric

jap42 · June 19, 2020, 11:19:34 AM

One of the fun things with a nice old bus is air leaks. I would like the door to be able to work even if I run out of air. I know I can manually open and close but I kind of like the auto open and close. I'm wondering if anyone has swapped the air cylinder for an electric actuator. I am thinking the setup that actuates the solenoids for the air could just be used to control a reversing switch to make the actuator go in or out. And then just let the built in limit switches stop the actuator. Some kind of spring mount so when the door closes the actuator can pull a few pounds of tension on that spring and keep it closed tight.

Does anyone know how much force the air cylinder has? I cant imagine I would need more then a 500# actuator. 4-6" travel.

Jim Blackwood · June 19, 2020, 12:15:14 PM

A 2" cylinder on 100# of air will make about 300# of force.

Jim

jap42 · June 19, 2020, 03:52:39 PM

So maybe a little more on the electric, 500-800# to make sure its not over working. The same spring setup may be helpful in preventing damage if the door gets stuck.

My cylinder is strange, it is almost like two cylinders in tandem. Its a little hard to follow the nest of hoses but I think one moves the cylinder and the other maybe acts as a dampener? For an air cylinder the motion is very fluid.

oltrunt · June 19, 2020, 04:46:58 PM

You could be right. I'd be interested in seeing a pic if possible. Thanks, Jack

luvrbus · June 19, 2020, 05:47:56 PM

Quote from: jap42 on June 19, 2020, 03:52:39 PM
So maybe a little more on the electric, 500-800# to make sure its not over working. The same spring setup may be helpful in preventing damage if the door gets stuck.

My cylinder is strange, it is almost like two cylinders in tandem. Its a little hard to follow the nest of hoses but I think one moves the cylinder and the other maybe acts as a dampener? For an air cylinder the motion is very fluid.

Those cylinders do have oil is why they are so fluid

jap42 · June 19, 2020, 06:52:15 PM

So I decided to look up the diagram for the door system. So yes, the door actuator does have a hydraulic portion that both dampens the motion and locks the door when it stops. The air is controlled by a 4 way valve. I can replace that valve with a relay (I need to convert to 12V anyway) which will switch the power back and forth to change the direction of the actuator.

buswarrior · June 19, 2020, 07:27:25 PM

The later model mci ha ve electric actuators.

E and J, and no doubt the 4505's too.

Happy coaching!
Buswarrior

jap42 · June 20, 2020, 03:35:35 AM

Interesting, I wonder if they would drop in place or if the setup is different under the dash.

I think the stroke is about 6 inches. Theres not much in that size over 300#. Most are 225#. Judging by the hydraulic portion of the air cylinder I would say the 300# force the cylinder would have is used mostly to overcome the hydraulic resistance. I am thinking opening the door may not take as much. The other issue is speed. The door now goes from full close to full open in about 3-4 seconds depending on the air pressure. Most of these actuators move 10mm/second. Thats about 20 seconds for a full stroke. A slow opening door can build suspense but that might be excessive. There are high speed models but they are only around 55#

My plan B is to add a second accessory tank with a check valve and a 110V compressor that will keep that tank topped off. I only have one little are leak in the unload valve which is pretty easy to replace with a standard push pull valve.

luvrbus · June 20, 2020, 07:09:18 AM

You have a lot of options on the door , the self closing door has been a option for years they are neat till one goes haywire,road noise and leaking air around the door is going to be your biggest challenge .My Rv has a air seal around the door when you shift to drive it airs up lol that is going to be fun to repair when it fails just keep it simple

lostagain · June 20, 2020, 07:28:13 AM

Speaking of keeping simple, I would just keep the bus aired up with a portable compressor, which most of us carry anyway.

JC

Jim Blackwood · June 20, 2020, 10:12:15 AM

The DL's also have a big latching pawl that grabs the edge of the door and clamps it down. That also is air powered.

I don't know where you are going to find an electric linear actuator to do what you want, and it will probably be expensive, although I don't doubt it'd be handy. When air pressure drops off the door can be grabbed and pulled open but it does take some effort. On the face of it electric does seem like a more elegant solution. A more old school method would be an electric motor and threaded rod to run the door open or closed. But one nice thing about the air system, all the safeties are built in.

Jim

jap42 · June 20, 2020, 11:54:58 AM

Keeping the whole bus aired up is defiantly an option. And with some of the newer quieter air compressors that is more likely the best option. Once I get my relay valve and blower belt tensioner replaced that will likely be the Route I go. Right now I am loosing all my air in about an hour or two. My airbags are empty in about another hour. I don't want that kicking on every 20 minuets to add air.

The A3 has the latch also, but it only latches when the master power is on.

lostagain · June 20, 2020, 12:14:11 PM

Once your air leaks are fixed, you should only have to run an auxiliary compressor once a day for a few minutes to keep up.

When you're loading a hockey team after a game in cold weather and you are not allowed to idle, you can open and close the door a hundred times on the air you have on the bus.

JC

jap42 · June 20, 2020, 12:43:31 PM

As cheap as a little Husky compressor is I may just install it between the Aux tank and the door with a check valve. I just know there are going to be a bunch of little leaks that I will not be able to hunt down. But if I eliminate the big 3 I should be doing much better.

Thanks for all the input! I guess I will table my actuator idea for now. Until the air cylinder goes, then I will revisit it.