Need help with my 6ws conversion

[ColdFox]

Hi fellow scalers,

I want to convert my 6x6 to 6 wheel steering because having 3 locked axle and stock scx10 steering doesn't make great turns

I'm on a budget, and don't really know what to do...

I currently own a DX3E, and already use the 3rd channel. I was thinking of putting the 3 servos on the same channel, but not sure it'll be very good at trailing speed.
Other problem is servo reversing:
front and center axle servo horn facing front
rear axle servo horn facing rear

I've heard reversing Y harness aren't a good idea, that's true right ?

I saw this thread, but I'm kinda scared of fuc*** up a servo
Step by Step Servo Reversing

Or is there a cheap TX I could get that can manage 3 servo steering ? (hacked GT3C maybe ? )


The servo I want to get is this one
https://hobbyking.com/en_us/goteck-h...12sec-53g.html
And the Hobbywing 20A (not sure what it's worth)
https://hobbyking.com/en_us/yep-20a-...___store=en_us
I'll get cheap CVD, knuckles and C Hubs straight from china


Thanks for your help, because I'm completely lost right now

[Hydrocarbon92]

I'd actually recommend 4ws. Keep the middle axle straight, reverse the rear servo, and have the mount point further up the servo arm. This way it basically pivots over the middle axle.

For example the Russian ICBM haulers have the 2 middle axles fixed and add more steering angle the farther from the middle: http://www.abc.net.au/news/image/529...x2-940x627.jpg



If you do get a radio that mixes channels, I'd do front servo on one channel and y-harness the two rear. That would let you use any 4ws-capible radio and be very simple (if the radio is easy to program).

Reversing the front and using a 1-to-3 y-harness would be a good idea too. You may need a signal booster like what Spektrum offers for $10, but it depends on the receiver & servos. I reversed a servo for my 4ws clod about 20yrs ago before fancy radios and 4ws controllers and the servo still works. May not be a bad idea to use a cheap/used servo to practice on. Just keep in mind if that servo has the pot & motor soldered directly to the board it won't be easy, but that model is probably like most Chinese 20kg servos with a direct pot but wired motor.

As far as that UBEC, that's one of the best options I've found. There's also a Hobbywing 10/20A UBEC that's great, but more expensive. Both will do a continuous 10-12A and 20A max for short bursts.

[ColdFox]

I'm quite sure the rear tires will rub on the center ones if I go 4ws, because they're really close and I'm running +12mm hex spacers.
Putting more space between axles isn't much of a choice because of the body


Does the rear axle need to steer as much as the front ? I'll try to see if I can get a few milimeters between tires
4ws would be very cool for the budget, because I wouldn't have to buy twice the parts...


I forgot that some servos have the pot directly soldered, thanks for pointing that

And for the signal booster, I'll try to get one

[Hydrocarbon92]

You don't need much more than 50% IMO, 100% front & rear will give you a turn radius about the same as your overall wheelbase. At moderate to high speed you do not want much rear steering since it whips the rear around. The 4ws controller I'm developing will let you adjust the ratio vs front as well as endpoints, but ratio can be adjusted with the servo horn too. You can also use weaker rear servos if you adjust via servo horn since leverage increases.

The biggest issue with direct-pot is just getting access to the screw holding the pot down. Usually you need to de-solder the motor, which you'll do anyways. After that you can just clip the outer leads and re-connect wires. The last 30kg JX servo I pulled had a recess in the circuit board to access the screw, while the last Savox I did required desoldering both the pot AND motor. The 20kg JX had a wired motor & direct-pot and the 20kg Tower Pro was wired for both.

[heyok]

If you had a spare channel, I'd suggest using my controller:
4 Wheel Steering Controller
4 Wheel Steering Controller - controlled by a two position third channel



Of course you might have to to the servo reversing as Hydrocarbon92 described.

Hydrocarbon92, your controller sounds interesting! Does it add anything more than my controller?

[ColdFox]

Unfortunately I don't have a spare channel, because my TX is 3ch and the third one is for the 2 speed gearbox.

I've messed a bit with links length this afternoon, and I think I can get the rear axle to steer In that case I wouldn't even need to reverse any servo, because both servo will be in front of the axle they steer, but on the rear axle the steering links will be behind.

Thanks for your help ;)

[Hydrocarbon92]

Originally Posted by ColdFox

In that case I wouldn't even need to reverse any servo, because both servo will be in front of the axle they steer, but on the rear axle the steering links will be behind.

If the steering link is on the rear but the servo is also turned 180 degrees, the wheels will still turn the same direction. You need to mount the servo backwards if it's mounted to the axle. If it's up in the chassis it will work by mounting the servo behind the axle.

Originally Posted by heyok

Hydrocarbon92, your controller sounds interesting! Does it add anything more than my controller?

Actually I got back to working on it today. I got the onboard eeprom working months ago to save individual trims, but today perfected it & added the ability to set the ratio the rear turns for each mode.

[heyok]

Originally Posted by Hydrocarbon92

..snip..
Actually I got back to working on it today. I got the onboard eeprom working months ago to save individual trims, but today perfected it & added the ability to set the ratio the rear turns for each mode.

Sounds like a cool part.