Servo Reverser or 3-channel?

[kev187]

Hello

I am about to set up my new CR01 with Radio gear. I had to use the long bracket for my TLT-1 to reverse the rear servo.

How well do the SERVO REVERSERS work?



I am going with 4-wheel steering, front & rear Futaba S3305 High Torque servos. But I am going to try this inline reverser for the rear servo on a 2-channel set up.

Any thoughts?

Also how exactly does the 3rd channel on a 3-channel radio handle the rear servo, are they both connected to the steering? Is it worth my while to pony up the extra cash for a 3-channel radio vs a 2-channel & the $19 reverser?

Thanks in advance everyone!

I am looking forward to getting this kit running!

[Mriswith]

It's a y-cord with some fancy circuitry to reverse and adjust the center of one servo the opposite of the other. Just means rear tires will always turn with the frontbecause both servos will be plugged into the same channel on the reciever. I've used 'em before on a stock type Clod way back in the day. Worked well for me at the time.

If thats what you want then it would work. If you want to turn the rear seperately from the front, then you need a 3 channel radio.

On a 3 channel radio the rear servo would be connected to the Aux or 3rd channel. It's controlled seperately depending on the radio 3rd channel functions.

Bottom line, if you can afford the 3 channel radio, go with that. It gives you more options down road. As to which radio, you're gonna have to do some extra research, lots of options depending on you bank account.

[kev187]

Originally Posted by Mriswith

It's a y-cord with some fancy circuitry to reverse and adjust the center of one servo the opposite of the other. Just means rear tires will always turn with the frontbecause both servos will be plugged into the same channel on the reciever. I've used 'em before on a stock type Clod way back in the day. Worked well for me at the time.

If thats what you want then it would work. If you want to turn the rear seperately from the front, then you need a 3 channel radio.

On a 3 channel radio the rear servo would be connected to the Aux or 3rd channel. It's controlled seperately depending on the radio 3rd channel functions.

Bottom line, if you can afford the 3 channel radio, go with that. It gives you more options down road. As to which radio, you're gonna have to do some extra research, lots of options depending on you bank account.

Thanks so much

I was looking at the Futaba 2PL FM $90 + $19 for the reverser or $110 for the 3PM 3-channel.

Both the same price as I want an FM set up, never used one before. All my vintage Tamiya kits have Futaba Magnum AM's

Sooooo

with the 3PM, can I set the 2nd servo to steer the rear of the Cr01 as I steer the front servo, or do I have to steer the rear independently? Not sure how the auxillary works.

I truly appreciate the help!!!

[Mriswith]

The 3PM doesn't independantly control the rear steer, it mixes it. In other words the rear turns with the front BUT, you can select front steer only, coordinated steer ( rear steers opposite of the front for super tight turns ) or crab ( rear turns same direction as front ).

Here's some programing tutorials for the 3PM. The 3rd channel switch is only 2 position but with programming and using it's Condition 2 button, you can make it function as 3 position for other things like a winch or Dig. It's not an ideal radio for those but it can be made to work.

[kev187]

Originally Posted by Mriswith

The 3PM doesn't independantly control the rear steer, it mixes it. In other words the rear turns with the front BUT, you can select front steer only, coordinated steer ( rear steers opposite of the front for super tight turns ) or crab ( rear turns same direction as front ).

Here's some programing tutorials for the 3PM. The 3rd channel switch is only 2 position but with programming and using it's Condition 2 button, you can make it function as 3 position for other things like a winch or Dig. It's not an ideal radio for those but it can be made to work.

Thanks so much, looks like it makes a lot more sense to go with the 3pm vs. a 2-channel+ reverser. Will be a nice set up!

This is my 1st crawler, everything else has been pretty basic, even though I have owned about 25 kits over the past 20 years of my RC hobby.

[Joat]

Yeah with a 3pm fasst , you can have 3 modes, frt steer only, frt/rear steer in same direction-crabbing-, then frt and rear steer in opposite direction,I flip between the 2 rear steer options, find it handy.

[Bow3022]

just out of curiosity, couldn't you reverse the polarity on the servo in the rear using a regular Y harness? (Basically switch the red and black wires...wouldn't the servo then run in reverse w/o a servo reverser?)

[looseunit4x4]

thanks for the post , gave me the confidence to set up 4WS , purchased a 3PM and set up control , question , the trim functions don't seem to alter the trim of the steering , throttle trim works fine , any ideas?

[Joat]

Originally Posted by looseunit4x4

thanks for the post , gave me the confidence to set up 4WS , purchased a 3PM and set up control , question , the trim functions don't seem to alter the trim of the steering , throttle trim works fine , any ideas?

For which the front or the rear, you need to go into either the front which is the regular trims, or for the rear you need to go into the pmx and set the epa, I forgot how to adjust the trims for 3rd channel, it's in the manual somewhere.
On another not I am looking at maybe a 4-5 ch now

[quickster47]

Unless you are using some programmable servos, like the better Hitec ones that allow you to change the direction of the servo with the Hitec servo programmer, you will need a device that changes the direction of one of the servo signals.

Electronically, the pulses will need to move in opposite directions for four wheel sterring control.

Carl

[PumpkinPie]

You can turn the servo horn around so it faces down, attach the steering rod to the bottom instead of the top and will pull the wheels instead of pushing them, essentially reversing the steering. This is what I did on my CR-01:

[fatwoul]

Originally Posted by PumpkinPie

You can turn the servo horn around so it faces down, attach the steering rod to the bottom instead of the top and will pull the wheels instead of pushing them, essentially reversing the steering. This is what I did on my CR-01:

I did the same, and most of the time it worked fine. However, it's not considered good practice. There's a tutorial on here somewhere, and it explains how you want to keep the steering rod as parallel as possible to the axle and the rod that connects left and right wheels. Taking the steering rod off the other side of the servo horn makes it very un-parallel indeed.

I also found that by doing that, the geometry meant that the steering became biased to one side. That is to say that steered quicker and further to one side than the other on the reversed servo.

It is a cheap and straightforward solution, but it does seem to have several limitations.

[PumpkinPie]

Yes, you're right but it's an easy solution for casual crawling. You can move the servo rod to the bottom of the steering knuckle to make it more parallel, which makes it a bit better.

I did have the problem of the servo steering quicker when it was pulling the wheels than when it was pushing them, I didn't really know how to fix that.

[fatwoul]

Originally Posted by PumpkinPie

...I did have the problem of the servo steering quicker when it was pulling the wheels than when it was pushing them, I didn't really know how to fix that.

I wondered about whether you could compensate for it by maybe attaching connecting rod between left and right to different holes on each knuckle. Afterall, there are two holes to choose from, right? Maybe playing around with that might allow for, say, the left wheel to turn more or less than the right, which might compensate for the bias? Dunno, I'd need to re-assemble my rear steer but if you've still got yours set up maybe you could try it.

[PumpkinPie]

Mine is all in pieces, been waiting for parts from Junfac for 2 weeks or more... plus I had to return my towerpro servos because they were glitchy and my truck would steer itself, so I got nothing at the moment

I did think about trying your idea, it'd be quite difficult to get it set up perfectly though. I have ordered a heavy duty steering rod kit which may help a little, I'll report back if I ever get my parts.

[fatwoul]

Originally Posted by PumpkinPie

...I have ordered a heavy duty steering rod kit which may help a little, I'll report back if I ever get my parts.

JunFac? Yeah their fat steering rods are good.

[MonsterDDT]

I use server reverser ($15 bucks something?). It works great and I think it's the simpless solution. No need for 3 channel or upside-down-rod.

DT