Safety trim wiring in parallel

[Rob3782]

I believe the trim motor from Kitfox will draw only a little over 5 amps when running and 7 amps for a very short time when possibly starting or at the end of the cycle. It is very common for electrical manufacturers to under size their lead wires. 18 awg is large enough. Safety trim module is designed for more than just Kitfox’s trim motor. John McBean went through a lot to get them to redesign this for us.

[Flybyjim]

Is this trim module for a speed change in the trim motor depending on the speed of the aircraft? Is this in the build manual somewhere?

[Rob3782]

The Garmin servo has the speed reduction control built into it. It reduces the speed of the trim motors at higher flight speeds. Unfortunately Garmin tells you in their installation manual that the servo can only handle a one amp load. TCW has been building a safety module that prevents you from running your trim motor continually after it reaches the extent of its travel. So John McBean got TCW to build a module that would handle the higher amperage we need for our trim motor and lets Garmin control the speed reduction and has the safety circuit built in also. Some of this can be done with relays. It is a small compact module. I thought it was worth it. 2CDBF9C4-C100-4F29-8B52-46F97E14D9EF.jpg

[Flybyjim]

I see, are most trim motors used in aircraft of this high amp draw? I have a Ray Allen servo mounted in the horazonal stab of my Rans S7 for my pitch control and I believe it is a much lower amp draw, there is no need for a speed reduction in operation at any airspeed.
Thank you for this explanation, Is there a need to have the speed reduction on the SS7 Kitfox screwjack for pitch control.

[Rob3782]

From what I have read on the forum in the past there was a few discussions on how to slow the trim speed while at higher speeds. It must be a common thing because Garmin built it into their system.

[Esser]

It’s described as quick but manageable with quick blips instead of holding a switch down above 60mph without it. Not required but a nice feature since you can reverse polarity if you need to and has a feature to stop a runway condition.

[jiott]

IMHO the trim speed reduction option is one of those nice to have items, especially for pilots new to the Kitfox, but certainly not necessary. I quickly got used to quick blips of the trim switch, rather than pushing the switch. After 10 or so hours I felt just fine with the simple stock system.

As a pilot gains experience you figure out ways to reduce your workload and be lazy. The Kitfox SS7 takes off perfectly with 1/2 flaps and the trim set at cruise trim with no flaps. So once you figure out this sweet position for trim, just set it there prior to T/O, then when your T/O climb is done and you retract flaps, you will find that the trim is already set for cruise. You hardly have to touch it except for maybe a quick blip to fine tune it. Yes, if you are doing a long climb to higher altitude you may want to reset the trim for cruise-climb then level cruise. Normally at the altitudes I usually fly at, I just hold a little stick back pressure and a little more throttle till I'm up to 1500-2000' and then just release the back pressure and throttle and wa-la I'm level cruising. Never touched the trim switch (OK maybe a quick fine tune blip). Lazy flying-works for me.

The better option to spend your money on I think is the trim position indicator. Then it is easier to preset your trim at that sweet spot I spoke of above.