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Spar pin switch conversion question

John-G

Well Known Member
I was going to call Van’s support … but they are off to Oshkosh until August, so hoping a fellow RV-12 builder can help me out.

Just finished completing SB-00053 (no cracks found) and figured while the seats are out, this may be a good time to convert from the old spar pin magnet/reed switch to the newer micro switches ... because the reed switches have been acting flaky lately. I have the new spar switch kit which contains the micro switches and the F-00104 plates the switches mount onto.

However, the kit did not come with instructions on where to drill the two mounting holes into the flange on the F-1248 L&R arm rests to mount the F-00104 spar pin switch plate. My existing older F-1248 arm rests only have one tiny hole in them with the reed switches mounted behind the hole. The updated plans (page 31B-10 rev 1) says nothing about drilling holes into the armrest for mounting the F-00104 spar pin switch plate … it just says to mount the F-00104 onto the flange of the F-1248 arm rest using the hardware shown (two 8-32 screws).

My question is: Are the newer kits coming with the F-1248 arm rests pre-drilled for the F-00104 mounting plate? If so, can somebody please give me the approximate measurements to the center of the two mounting holes as measured from the center of the aft most rivet hole where the F-1248 is riveted onto the F-1204H bulkhead cap?

Or, if there is another location in the plans with a call out for the drilling, please direct me to it.
 
The magnetic reed switches work a whole lot better when mounted parallel with the magnets instead of perpendicular.
 
The holes are pre drilled in the latest kits. See attached. Maybe you can persuade someone with an incomplete fuselage kit to trace a template for you before they install their arm rests.
 

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Bob- Thanks for posting the attachment showing the new "new" spar micro switch assembly .... the kit I received has actual button micro switches as opposed to the standard micro switches shown in the drawing you posted. Looks like Van's has moved on to a third generation using a traditional micro switch like the ones used for the stall and canopy open sensors.

So if anybody has measurements for the push button micro switches it would be greatly appreciated.

Joe - You bring up a valid point ... I can see how the reed switches would work better if placed vertically. May just try that prior to just winging it and drilling holes.
 
... because the reed switches have been acting flaky lately.

The spar pin sensor on the right side has flickered on and off for the past few flights. I know it is the right because when the warning lights up I can pivot the safety arm closer to the side wall and the light goes off.

While there isn't much room for the safety arm to move it is enough. My fix was to install a zip tie in the hole of the catch to fill the empty space and prevent wiggle room of the safety arm.

A few flights later the "Spar Pin" warning has not occurred.
 
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