Master Contacter

[Bryan Cotton]

Bob,
Thanks for that info. Not a bad option.

Here is a picture of my steel key to replace the red plastic key. It started out as a tube. I found a bolt that fit snugly in the tube. There is a short piece of bolt inserted and a hole drilled through tube and bolt hunk. This hole is a light press fit for an AN3 bolt shank.


The switch and steel key weigh 4 oz. An aluminum tube to rivet to the steel key adds 2 oz. Add rivets, handle, and brackets will probably be another 2 oz to the assembly - one half lb. I am curious what a contactor weighs. Anybody?

[gammaxy]

This link says 13oz:

http://www.bandc.aero/continuousdutycontactor.aspx

[Bryan Cotton]

Thanks Chris! Seems like a good trade.

[Bryan Cotton]

Here I am engineering by making parts over and over until they come out right:


On the final bracket I'll have nutplates for AN3 bolts.


The brackets are offset 30 degrees so I can run my pushrod horizontal from the subpanel.

[n982sx]

When I started to make a few custom parts, I saw that Bob Mika used paper models. I did that for all of my Sonex custom pieces and it worked well. Saved on aluminum.

[racaldwell]

Hi Bryan,

How does the shaft for the battery switch get around the fuel tank? I don't have a front fuselage yet so I can't see for myself. I am contemplating the Flaming River battery switch that comes with an extension handle. But I already have a Sky Tek master contactor in the hangar that I am tempted to use out of simplicity sake. The one in my RV-6 has been holding up for almost 18 yrs & 960 hrs.

Still trying to finalize my power circuit.

Rick
Xenos 0057

[Bryan Cotton]

Rick,
I have not finalized it yet, but it is to the left and underneath. The handle will be on my subpanel.

[lutorm]

I'd also like to stop wasting 1 out of my 10 precious alternator amps on the master contactor. There are solid state "relays" that use essentially no current, something like https://www.mouser.com/ProductDetail/Cr ... 7kvuhYo%3d. Anyone tried this route?

The thing you have to watch for with solid state devices is that they're sufficiently protected from voltage spikes, these have maximum ratings of at least 50Vdc, but it would be possible to add an extra overvoltage protection on top.

[Bryan Cotton]

Here are a few pictures. First one is the mechanical switch.

Master sw

Here is the switch mechanism in the off position.

Off

And again in the on position.

On

I sacrificed a 1/4" drive u-joint from my socket set to make this work.

[Bryan Cotton]

A couple more pictures. Here is my u-joint welded to my steel key. The plastic key is shown for comparison.

Here is the handle I welded up. The guide is a loose fit, it keeps the tube from flopping on the floor. It bolts to the vertical extrusion that is in line with the instrument panel.

Weight is 10.5 oz missing the mounting bolt for the guide and 4 rivets. The 13 oz for the electric contactor would not include the master switch and associated wire. So the weight is close, the current draw is infinitely better.

Edit: there are two small firewall penetration guards I have to weigh too. So weight is very close to dead even.

Edit again: the electrical master will also need a penetration but you could argue it shares one with other wires.