4PL Throttle Trigger Travel Mod

[YJ_Driver]

I've had the 4PL for nearly a year now so I'm due to make a mod and void the warranty ;)

One thing I quickly noticed with the transmitter is that the reverse travel of the trigger is much shorter than the forward. This is fine for boats or cars that only use brakes, but for crawlers and scalers I find it limits low speed control in reverse. I took measurements with a protractor to find out what the stock unit offers.







I found the forward/reverse ratio to be about 75/25 (30 degrees forward, 10 degrees reverse). I'm used to my old radios that gave me 50/50 so I set out to change it.

The third picture above shows where it is being limited on the back stroke at the blue arrow; it's not even reaching the mechanical ATL screw at the red arrow. I decided to trim these two areas to maximize the travel. But first I had to make sure the radio could get 'adjusted' to the new throttle travel.

I took apart the trigger mechanism, took note of the pot (potentiometer) position at the reverse position and removed the trigger from the pot. I then went through the Adjuster process (p. 97 in the 4PL manual) turning the pot further back than I was planning for test margin. The radio had no problem adjusting, so all looked good and out came the X-Acto knife.

I trimmed the areas shown in blue and red below; I didn't remove the whole rib as I figure it's there to add stiffness. I re-measured the back stroke and figure I gained about 80% travel. Still not 50/50 but way better.







I re-assembled the radio and went through the Adjuster sequence a final time. Driving my cars I can really feel the difference, I have much better control in reverse than before. The nice thing about this mod is that if you don't like it afterwards or your radio can't adjust to the new reverse position, you can use the mechanical ATL screw to push it back, which makes me wonder why Futaba limited the stroke so much in the first place.

If you don't want to push the reverse stroke back like I did but still want a lower forward/reverse ratio, you could try adding a spacer at the yellow arrow shown in one of the pics above. This would push the neutral position forward reducing the forward stroke and incresing the reverse stroke at the same time. You'd need to go through the Adjuster sequence afterwards, oh and don't make it permanent until you're sure the radio will accept the new neutral position!

Richard

[Charlie-III]

Nice write-up, I'll pass it onto my son since he runs a 4PL.

[ninja turtle]

hey thats pretty cool. thanks for sharing. i need to do this once my warranty is up.

[asw27x]

cool but i cant see the pics

[YJ_Driver]

Charlie and Ninja, thanks for the comments, and the link in Harley's thread.

Originally Posted by asw27x

cool but i cant see the pics

What browser and version are you using? They're direct links to my personal gallery so I'd like to know if I should change something.

[Charlie-III]

Originally Posted by YJ_Driver

Charlie and Ninja, thanks for the comments, and the link in Harley's thread.


What browser and version are you using? They're direct links to my personal gallery so I'd like to know if I should change something.

No problem, just trying to keep most 4PL stuff in 1 thread (or, at least findable).

I also see my son found my email!

[I see the pictures.....]

[asw27x]

I'm using chrome but on my iPod I can see them I'll just use my ipod

[YJ_Driver]

Originally Posted by asw27x

I'm using chrome but on my iPod I can see them I'll just use my ipod

I don't have Chrome installed anywhere, maybe I'll try it sometime. Thanks for the info.

[asw27x]

Mod is done since I have pulled my radio apart before it took about 5 mins and can't wait to try it

[Prop Shaft]

I did this mod but also added a shim to get it closer to 50/50 (white styrene in pic). Its near spot on now but I found I could not calibrate it by using the adjuster mode after adding the shim. The pot reads full throw a short ways before it mechanically bottoms out in reverse. I still use it this way tho as it still works just fine with all my novak esc's after doing the 1 touch programming.

[ninja turtle]

Finally did this. Wish i would have done it a long time ago, literally took 5 minutes. Reverse is a lot smoother now. Thanks again YJ_Driver. Now i need to figure out the 3 position momentary switch mod.

[josh6575]

Thanks for posting. I'll give it a try.