H

Harold Lanfear

Well Known Member
I'm thinking about using an Radio Control servo to operate my heat box control instead of cable, which would be more difficult to route and connect. Has anybody done this before?

My current thinking would use a spring as a 'fail safe' device to close the door in the event of an engine compartment fire, etc. which may melt the servo.

I've gone as far as buying a servo and setting up a test module. It works quite well set up as with a one inch arm, providing a two inch throw.

Any thoughts?
 
Voltage

I briefly thought about using R/C servos, but discovered they use 5 or 8 volts (IIRC). How did you solve the voltage problem?
 
Automatic controll !

As with modern cars, you could use a thermostat to control the servo. You set the temperature and the thermostat opens and closes the valve, keeping the temperature in the cabin at the preset value. Very important is where you put the thermostat (direct sunlight, etc.).

If you use a two-way valve, with an additional cold air inlet (see Van's Websyore), you could controll the temperature realy well, even in the summer.

For additional safety, you could also put a temperature seonsor in the engine compartment, allowing the servo to automatically close the heater valve if the temperature reaches a certain value (fire). I would include the spring in any case.

Instead of the RC-servo, you could use a Ray Allen servo, like we use for the trim. Might be a bit more expensive though.

Actually I had planned for the above setup, but had to return the two-way valve and use the ordinary heater box, because I am using the Vetterman mufflers and they require air going through them at all time, which was not possible with the two-way valve, since it closes off the air completely in the off position.

Regards, Tonny.
 
Cabin Heat Valve

I used an R/C servo and Perihilion's general purpose servo controller...



Better pictures and a video somewhere, but I can't find them...

It works in the garage, but I'm not flying yet.
 
Thanks

Thanks to all for good ideas and comments. I'll think I'll move to use the servo vs. cable, given my space issues. The RC servos are smaller than Ray Allen's, and cheaper; given that my will be in the engine compartment. The RA would provide postion sensing, but I really don't need that. I'll post details when I get a final setup. H
 
a word of caution on RC servos

I built a robotic Halloween display for a friend that owns a bar here in San Francisco, and after 4 years ran into some trouble that you might want to know about.

The display uses 4 servos to tug on preloaded fishing line in order to move several rats around a wall. each servo was attached to it's line via a key ring at the end of a 5 inch (light) plastic arm. the rats would be taken down each year, but the servo control module would stay up as it could not be seen from the ground.

after about 4 years of sitting on the wall (with Halloween '07 off), I discovered this year ('08) that several of the servos had worn in 'detents' in the gearing. I call them detents only in that this is what they feel like when you slowly backdrive the servos through their full range. in practice the servos are shot, and have to be replaced. I'm not sure of the source of the failure. ....perhaps they did not like sitting for 2 years with a VERY slight load on the gears (the arms were in a vertical plane). ....perhaps such local gear wear would not occur with constant usage. again, this happened to several independent servos.

I will disassemble them to look at the state of the gears.

I just wanted to give you a heads up, as I think you'll definitely want to have the servos accessible for replacement if need be (for this and other unknown failure modes).

on the flip side I built a control system for work that uses many servos and they've been in operation for 9 years.

Note, they do have metal gear and ball bearing upgrade kits for off the shelf servos. you might want to look into this as some of those plastic gears are pretty soft.

-john
 
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