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Help! Need clever ideas to modify radio for special needs child

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Help! Need clever ideas to modify radio for special needs child

Old 05-30-2022, 11:05 AM
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Default Help! Need clever ideas to modify radio for special needs child

Hi All,

Looking for some help making RC more accessible and enjoyable for a special needs boy in my family.

TL;DR:
8-yr old boy in my family has physical challenges with his fine motor skills (no other issues, and he's fine cognitively). I need help with ideas for how to modify his radio such that turning requires much more than the standard amount of transmitter steering wheel input (which by my estimate is approximately 1/8 of a turn). Ideally, reaching full lock would require 1/2 or even 3/4 of a turn of in order to reach full lock from the center position. That would make it much easier for the boy to control his RC.

Any ideas? Thanks in advance!

DETAILS:
I need your help making RC more accessible for a special needs boy in my family. The controls on a standard transmitter have rather short throw (which is just fine for most of us) and the boy can't operate them with enough fine control to get low speeds, partial turns, etc. As a result, his driving is basically "on/off" for both throttle and steering. Amazingly, he manages to get around the yard and the street without constantly hitting things, but driving this way isn't much fun and he can't do things like line up his truck for a jump.

The boy is 8 yrs old, about average size, and has no trouble holding a normal transmitter or reaching the throttle and steering controls. His hands are not large enough to allow him to hit 'reverse' on the trigger with just one hand (he has to remove his steering hand and use that for assistance) but that's NOT the source of any fundamental problem. Also, he has no cognitive issues and he can fully understand the idea of turning the wheel halfway in order to make the car turn in a wide circle (for example), but he just can't execute that.

I have mitigated this issue on the throttle channel by simply setting the EPA at a very low setting, so his top speed is manageable and he just drives at that one speed. However, that kind of crude solution doesn't work well for steering - he needs the full range of steering, but he needs it to be available over a much larger throw range on the transmitter steering wheel.

I have thought through and experimented with all the settings we use for ourselves (D/R, EPA, expo, servo speed) etc and none of those solve the boy's fundamental problem, which is that he doesn't have the dexterity to turn the transmitter steering wheel in tiny increments. The entire range of motion on the transmitter wheel is perhaps 1/8 of a turn (so our adjustments are necessarily small fractions of that). That's totally impossible for him. I'd like to find some way to make the transmitter wheel turn say 1/2 or even 3/4 of a turn to fully deflect the car's wheels.

I am willing to perform minor surgery on my (cheap) radio to make this happen, and I'm "decent" at mechanical work (probably average for people who have been in RC for a long time).

I appreciate your help and ideas!

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Old 05-30-2022, 11:26 AM
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Interesting problem - the wheel is probably attached to a pot and I'm not sure how you would increase the throw on the pot. I wonder if you could offset the steering wheel and use gears or pulleys to change the ratio? My other thought is to use a longer arm on the steering servo which will slow down the steering, but you would need to add throw back in the radio.

Post some more details - which radio, car?

I'm in San Jose, and have a 3D printer and a small 2D CNC machine, and some CAD skill - let me know if I can help.
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Old 05-30-2022, 12:46 PM
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There's a guy locally that races with some adaptive devices for the throttle. Not sure if he does it for steering too. Feel free to PM me your info, and next time I see him, I'll pass your info along.
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Old 05-30-2022, 12:58 PM
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belewis01 That's so generous of you to offer. Sounds like we're local so I'll drop you a PM.

As to your other questions, the vehicle is an Arrma Granite and the radio is a stock radio (Tactic some or another). I also have a Radiolink RC6GS transmitter which is pretty full-featured but also pretty cheap, so it is great candidate for surgery with no concern of failure. I think your idea of trying a mechanical solution (ie maybe some gears in a circular arrangement) might work.

On the servo issue, I don't think a longer arm + slower speed will work. I can add more throw at the radio, but 100% of the throw always happens within the same 1/8 turn of the physical steering wheel. That 1/8 turn is the problem - it is quite small. I can slow the servo down electronically or mechanically, but that doesn't help, as he still ends up turning all the way, no matter what. He even calls it "going crazy" and he asks me why my car doesn't "go crazy" like his car (his car whips back and forth, as you would expect).

Thanks for the questions and ideas!
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Old 05-31-2022, 12:27 AM
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One simple solution is just to increase the size of the steering wheel, the largest wheel that he's comfortable with would be a good idea. A 2WD buggy front, stadium truck wheel or even a 1/8 buggy wheel and tire might do the trick. If you're able to get the assistance mentioned above, 3d printing an adapter from the radio's potentiometer to match the preferred wheel's hex size might work well.

Another option to consider might be using a stick radio. It is relatively simple to extend the sticks which would also have the effect of making requiring larger movements of the stick ends to get the same amount of steering from the car.
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Old 05-31-2022, 08:42 AM
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The steering pot is just a variable resistor. I wonder if you could use a different value pot, and/or a stronger (or weaker?) resistor in series (or parallel) then eliminate the physical wheel stop. That way he could keep the same sized wheel but have a greater range to turn it. You could even put a knob on the wheel that he could grab on to. Any electronic engineers here to work out the resistor values?
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Old 05-31-2022, 10:27 AM
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Originally Posted by Bsthetech View Post
The steering pot is just a variable resistor. I wonder if you could use a different value pot, and/or a stronger (or weaker?) resistor in series (or parallel) then eliminate the physical wheel stop. That way he could keep the same sized wheel but have a greater range to turn it. You could even put a knob on the wheel that he could grab on to. Any electronic engineers here to work out the resistor values?
This was one of my thoughts as well, but I have very limited electronics skills.

It's an interesting problem, I wonder how many really notice that the wheel only turns about 20 degrees per side?
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Old 05-31-2022, 10:42 AM
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Originally Posted by belewis01 View Post
This was one of my thoughts as well, but I have very limited electronics skills.

It's an interesting problem, I wonder how many really notice that the wheel only turns about 20 degrees per side?
Ya I'm thinking once he had a wider motion range he could then fine tune the control with Expo.
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Old 05-31-2022, 01:26 PM
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not sure but would this thread be any help? https://www.rctech.net/forum/electri...eeds-user.html
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Old 05-31-2022, 01:41 PM
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maybe a drop down type wheel add on. with a 2 pully . top at 2x .smaller one joined with a O ring. made from carbon fiber..
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Old 05-31-2022, 11:29 PM
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Thanks everyone for these great ideas! I'm pursuing a few paths and we'll see what happens. Much appreciated.
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Old 06-08-2022, 03:28 AM
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Digi radio should be able to adjust the exponential almost infinitely to achieve the effect you're after, as well.
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