4WS with Spektrum DX5C frustrations

[SMT_Digger]

Hello everybody,

New guy here. Don't have a crawler yet but one is in the future. What I do have though is the Axial SMT10 Grave Digger that I've purchased for my son and have been slowly modding it to be pretty awesome, but have hit a hiccup with the 4 wheel steering. I know this isn't a monster truck forum, but since 4WS can be a common thing in the crawling world I figured I would come here to see if I can get some help.

So I've upgraded the electronics in the truck, to include a hobbywing max10 4000kv brushless combo, Spektrum DX5C transmitter with spektrum 6100 5 channel receiver. It has AVC but I'm not using it for my application. Ive molded the rear AR60 axle with the knuckles and axle pieces to accommodate rear steering, along with beef tubes on all axles, upgraded links/trailing arms, jconcepts tribute wheels with goldenyears tires, and GPM tie rods/steering linkage. The rear servo has the axial 23t aluminum servo horn, and the front has the stock servo saver, which is very stiff i might add. A servo horn to match the rear is on the way. Both servos are Spektrum 614s.

The problem I'm having, is getting the steering aligned. After binding the transmitter and setting steering and throttle end points, the front axle wants to turn to the left. To get this straight, I have to adjust the trim so somewhere around 70-80 to get it to track straight. To add to this, when setting up the 4ws with the rear in aux3 set to button D, it also wants to turn and requires around 30 in the sub trim to get it centered.

So the next problem that I cant figure out, is how the steering trims are adjusted with each other between the two different channels. In the 4ws setup, I have position 0 as front wheel steer only, position 1 is 4 wheel steer, position 2 is crab steer, and position 3 is rear steer only.

Here is the frustrating part. When switching between modes, the axles want to re-enter at different positions. I then have to adjust the trim and sub trims again to get the truck to track straight, and then when I switch back to the previous mode, the trim is off again. I cant figure out what is linking the channels and why its different for each position of the D switch.

I'm going to try adding a second model to the transmitter, and re-binding the receiver again, starting with everything at 0. Once the servo centers itself after binding, I will attempt to straighten the wheels and re-attach the servo horns as close to 0 as possible.

Any suggestions?

Digger

 

[HumboldtEF]

Shoot thats an odd one, the servo shouldn't be finding a new center for each mode like that. Hopefully starting over with a new profile will resolve that.

 

[23drumerboy]

Hello everybody,



New guy here. Don't have a crawler yet but one is in the future. What I do have though is the Axial SMT10 Grave Digger that I've purchased for my son and have been slowly modding it to be pretty awesome, but have hit a hiccup with the 4 wheel steering. I know this isn't a monster truck forum, but since 4WS can be a common thing in the crawling world I figured I would come here to see if I can get some help.



So I've upgraded the electronics in the truck, to include a hobbywing max10 4000kv brushless combo, Spektrum DX5C transmitter with spektrum 6100 5 channel receiver. It has AVC but I'm not using it for my application. Ive molded the rear AR60 axle with the knuckles and axle pieces to accommodate rear steering, along with beef tubes on all axles, upgraded links/trailing arms, jconcepts tribute wheels with goldenyears tires, and GPM tie rods/steering linkage. The rear servo has the axial 23t aluminum servo horn, and the front has the stock servo saver, which is very stiff i might add. A servo horn to match the rear is on the way. Both servos are Spektrum 614s.



The problem I'm having, is getting the steering aligned. After binding the transmitter and setting steering and throttle end points, the front axle wants to turn to the left. To get this straight, I have to adjust the trim so somewhere around 70-80 to get it to track straight. To add to this, when setting up the 4ws with the rear in aux3 set to button D, it also wants to turn and requires around 30 in the sub trim to get it centered.



So the next problem that I cant figure out, is how the steering trims are adjusted with each other between the two different channels. In the 4ws setup, I have position 0 as front wheel steer only, position 1 is 4 wheel steer, position 2 is crab steer, and position 3 is rear steer only.



Here is the frustrating part. When switching between modes, the axles want to re-enter at different positions. I then have to adjust the trim and sub trims again to get the truck to track straight, and then when I switch back to the previous mode, the trim is off again. I cant figure out what is linking the channels and why its different for each position of the D switch.



I'm going to try adding a second model to the transmitter, and re-binding the receiver again, starting with everything at 0. Once the servo centers itself after binding, I will attempt to straighten the wheels and re-attach the servo horns as close to 0 as possible.



Any suggestions?



Digger

I noticed on my Danchee Ridgerock MOA 4ws rig, sometimes this same issue would crop up...only way i found to correct it was to use f & r steer trim knobs IN EACH of the 4 modes, and/or put it in 4ws mode, adjust, change mode... Also, i believe if your servos are being OVER powered, say, 2s-rated V-wise, and you are running 3s, you can run into "jitter" such as described.

Read-Up! Mod-On! Crawl EXCESSIVELY!

 

[DrIsotope]

Did you go through the long, poorly described process of fully disabling AVC? Because if you didn't, I'm gonna say that's the most likely culprit.

Sadly, it can't just be "switched off"-- it's awful, convoluted, and requires rebinding the receiver to the Tx two times.

The 6100/6200 receivers are simply not worth the headache, IMO. Setting up 4WS on the SR515 takes like 2 minutes.

 

[SMT_Digger]

I noticed on my Danchee Ridgerock MOA 4ws rig, sometimes this same issue would crop up...only way i found to correct it was to use f & r steer trim knobs IN EACH of the 4 modes, and/or put it in 4ws mode, adjust, change mode... Also, i believe if your servos are being OVER powered, say, 2s-rated V-wise, and you are running 3s, you can run into "jitter" such as described.

Read-Up! Mod-On! Crawl EXCESSIVELY!

I'm only using 2s batteries at the moment, and do not have the bec set for high voltage servos. It is odd how it changes. I can even see it in the graphs on the display, how the trim number changes between steering modes, and ive not adjusted those trims in the different steering modes that I know of. From what I can tell, adjusting the sub trim effects all the steering modes.

Did you go through the long, poorly described process of fully disabling AVC? Because if you didn't, I'm gonna say that's the most likely culprit.

Sadly, it can't just be "switched off"-- it's awful, convoluted, and requires rebinding the receiver to the Tx two times.

The 6100/6200 receivers are simply not worth the headache, IMO. Setting up 4WS on the SR515 takes like 2 minutes.

I did not do this, as I didn't think I would need to switch it off. I assumed it would default to off. I will have to look into this. I had the option of the transmitter bundled with the 6100, or the transmitter/515 receiver separately for the same price. I chose the bundle thinking that I may later swap out the 6100 into my granite for the AVC and to be able to use my dx5c for both models. I may go ahead and pick up a 515 and do that.

The project is on hold at the moment, awaiting a new aluminum servo horn. I took the stock servo saver off and used the cheap plastic horn that came with the s614 servo, and these big tires shredded it within 10 minutes of running.

I'm also considering upgrading to a heavier duty servo. Maybe a 25kg and one that will accept high voltage. That will help keep the wheels straight when bashing, i think.

Digger

 

[DrIsotope]

The AVC is absolutely on by default. I made the same, Oh AVC will be optional thought when setting mine up-- and long story short, it took several days and numerous YouTube videos to even get my rig to have reverse.

I did the same combo because I was lured by the telemetry on the 6100. Needless to say, every other rig paired to that radio has a 515 in it.

 

[Voodoobrew]

The reason you need trims is because your steering arms are the wrong length. The best way would be to zero the trims then adjust the steering arms.

There are also endpoints to set on the remote to have an equal left and right turn radius.

I am surprised you need to keep adjusting trims. I don't remember needing to do that.

You are using the built in 4wheel steering functions? Or manually setting it up?

Subtrim might be the trim you are supposed to start with. There are 3 types of trim.
One moves the whole range over so left and right have 100% travel each.
One moves the center only so left and right have different range %
One sets the max range for left and right.

I don't remember their names. But spectrum might label them different than most

Sent from my SM-N986U using Tapatalk

 

[MOguy]

I have 4ws with the Spektrum DX5 Rugged. I have the set up on its own 3 pos switch operating independently.

I just set up the switch and the endpoints and that was it.

 

[SMT_Digger]

The reason you need trims is because your steering arms are the wrong length. The best way would be to zero the trims then adjust the steering arms.

There are also endpoints to set on the remote to have an equal left and right turn radius.

I am surprised you need to keep adjusting trims. I don't remember needing to do that.

You are using the built in 4wheel steering functions? Or manually setting it up?

Subtrim might be the trim you are supposed to start with. There are 3 types of trim.
One moves the whole range over so left and right have 100% travel each.
One moves the center only so left and right have different range %
One sets the max range for left and right.

I don't remember their names. But spectrum might label them different than most

Sent from my SM-N986U using Tapatalk

I'll have to look further into that and re-read the manual. By steering arm, are you referring to the arm that goes from the servo horn to the steering link? If so, mine is not adjustable. Im thinking about swapping it for an adjustable one though. This is the one I have on both front and back. It says its adjustable but the arm isn't, just the linkage.



I did pick up a 515 receiver today, and will be swapping that out. I may put the 6100 in my granite blx.

On a side note, im curious if the sheer size of these goldenyears tires are pushing my servo. I was running it tonight in the driveway after replacing the worn nylon servo horn, and once I get any speed, the front tires want to veer off, mostly to the right, but sometimes left as well. The servos im using are spektrum s614, and they only have 14.5kg of torque. Would it be better to upgrade to some digital servos that will run at 7.3v and switch my bec to high voltage? Something along the lines of 25kg or even 35kg?

Digger

 

[Voodoobrew]

Yes that rod. I have adjusted them by changing the horn in the servo, bending the rod, tightening or listening the rod ends, even cutting them down and retreating the ends. Lots of ways to adjust them.

Sent from my SM-N986U using Tapatalk

 

[SMT_Digger]

Well,

It seems swapping out the receiver and the servos may have done the trick. She tracks very straight now with only little adjustment to the trims. I also swapped the steering linkage from the GPM pieces to Vanquish pieces. They are adjustable with the rod ends.

It was running great until I rolled it. Now once I get up to speed it acts like its getting loose somewhere. Kind of like pulling a trailer and getting really bad swerve like the rear end is fishtailing but not losing traction. Back to the drawing board.

Digger