Kevin Warnock

Linear actuator

I’m in the middle of converting an RTS bus to a motorhome. I read Bus Conversions Magazine to learn construction techniques. The discussion forum hosted by Bus Conversions Magazine is outstanding, and I visit this forum daily.

Sadly, some bus conversions burn to the ground.

What a tragic event that would be if it happened to my bus conversion.

These things really represent a lot of work, and getting a check from the insurance company would still mean you’d have to duplicate a lot of work to make a new one. Yes, you could buy an already finished conversion, but there won’t be another conversion anywhere in the world like mine when I’m done with it, it’s going to be that unusual.

So I want to make it very unlikely my bus will ever burn to the ground. I’ve already talked about putting the generator on the roof in a previous post. That should help a lot since many bus fires start in the generator compartment, typically in a storage bay, and burn up from there. If any fire started on the roof, it would be hard for it to burn down, especially since the box I will put the engine in will be made of metal and lined with cement board and rock wool type insulation that can’t burn. I will also put auto closing trap doors on the air inlet and exhaust, so that if there’s a fire, oxygen to the box will be shut off in seconds, which should snuff out any fire almost immediately.

Another big source of bus conversion fires are electrical fires. To limit the chance of an electrical fire, I am not going to install many wires in the ceiling and exterior walls, which will be insulated with spray foam. Spray foam is highly flamable, and when it burns, it makes toxic gas that can kill you very quickly. So I will keep most of the wires I add inside metal conduit elsewhere that’s not close to spray foam.

The manufacturer of my RTS, TMC Corporation, ran several large bundles of wire in the ceiling, and these are required for the vehicle to run at all. There are perhaps 100 conductors, and it would be risky to try to make them longer so I could run them somewhere else, so I will leave them in place. However, I am looking into encapsulating them in a fire stop product.

The above precautions are straight forward. What I’m going to write about today is less straight forward, and I would like comments as to whether what I’ve dreamt up would be a good idea to implement.

I’m considering installing smoke detectors that include a relay to control unrelated circuits. If the alarm trips, a totally separate electrical circuit can be closed or opened, depending on how you wire the relay.

What I am thinking about doing is using the smoke detector to control a set of motorized linear actuators that would be installed next to and attached to the actuation paddle of each of the master circuit breakers and master battery disconect switches on board. When the actuator is engergized, and motor inside it turns some gears which cause a plunger to move in a straight line for x number of inches. When the polarity of the energizing power is reversed, the actuator plunger moves in reverse. In this way, formerly manually operated switches and circuit breakers are now electrically controllable.

My RTS before the conversion was started had 2 master battery disconnect switches, in the battery compartment. These switches take some effort to push, thus my selection of an actuator that can push or pull 100 pounds. I would not allow the actuators to operate these main vehicle power switches when the bus conversion engine is running, since it could be dangerous to shut down the engine while underway, even if there’s a fire on board somewhere.

My RTS after conversion will additionally have 3 master circuit breakers, as follows:

1. AC shore power master breaker
2. 24 volt house battery bank master breaker
3. 12 volt house battery bank master breaker

If all 5 breakers were shut off in the event of fire, it would seem that an electrical fire might not get as far as if there were power flowing. What I don’t know though is if an electrical fire has caused enough smoke to trigger a smoke alarm, does that mean that even if the power is switched off that it will accelerate or continue burning?

Of course, it could be traumatic if you’re cooking dinner at night, set off a smoke alarm and are plummeted into darkness. But I almost always have my phone with me, and that doubles as a flashlight, so I’m not that worried about that. In addition, the System Sensor manufacturer of detectors I linked to above offers a model that has two degrees of alarm severity — smoke and heat. A local alarm is triggered with smoke alone and a general alarm is triggered when the built in heat sensor is activated. This might be the model to install in the kitchen/living room compartment of my 4 compartment bus conversion. Many of the System Sensor detectors run on 12 or 24 volts direct current, perfect for a bus conversion, and can be networked together so they all make noise when one activates.

System Sensor brand smoke and heat detector with external relay

Another downside is a small fire might be safely extinguished with a garden hose, which will need the pump active to pump water. But I would make it easy to reverse direction of the linear actuators so I could turn the power back on quickly, and I could have a dedicated circuit for the water pump that wouldn’t be shut off in the event of fire.

There probably is a good reason not to implement this idea, because if it was such a good idea, why isn’t it implemented widely in buildings? Linear actuators are cheap and plentiful, as are networked smoke detectors that can switch external circuits. If this idea were required by code, the price of these items would plummet, like what must have happened with ground fault circuit interrupters, which are so inexpensive I can hardly trust them, given how critical it is that they work for decades without attention.

However, there’s a chance this idea hasn’t been seriously considered and tested. I would love to start a debate in the comments here or on the Bus Conversions Magazine discussion forum, where my member name is ‘Kevin Warnock.’

PS – I want to express my condolences to Mike Sullivan, the CEO and President of Bus Conversions Magazine, who lost his Mother Dorothy Sullivan today.