PLEASE HELP...steering servo hits "everything"???

[XFITCRAWLER]

Hello all,

I'm new to the crawler scene and can't wait to get my new SCX10 Rubicon up and running.....having serious (at least "I" think it's serious) clearance issues with the Hitec 645 servo. I have it mounted on the axle as the instructions say and the first thing I noticed was the servo arm hitting the crossmember. I've searched all the forums and looks like this is a common problem so I shaved the mounts to move the servo back. This is good now BUT I noticed that I can only get about half suspension travel when the axle is articulated on the driver side....with the left side of axle pushed up and the wheels turned left, the top steering rod hits the frame with only half travel!!!!! I didn't see anything in the forums about this problem. The front drive shaft also hits the y-brace with the front left axle pushed up.....is this normal? Everything's built the way the book says...super easy! Just don't understand why there's so much interference up front especially with the axle articulated (left up) as everything hits????

Thanks all for any help!

[JeepExplorer]

Should post a picture... I just trimmed some of the cross member out last night, all I did was the 4 link on the front axle and it rotated the axle enough that it was just catching on the crossmember.

[1beatjeep]

Originally Posted by XFITCRAWLER

Hello all,

I'm new to the crawler scene and can't wait to get my new SCX10 Rubicon up and running.....having serious (at least "I" think it's serious) clearance issues with the Hitec 645 servo. I have it mounted on the axle as the instructions say and the first thing I noticed was the servo arm hitting the crossmember. I've searched all the forums and looks like this is a common problem so I shaved the mounts to move the servo back. This is good now BUT I noticed that I can only get about half suspension travel when the axle is articulated on the driver side....with the left side of axle pushed up and the wheels turned left, the top steering rod hits the frame with only half travel!!!!! I didn't see anything in the forums about this problem. The front drive shaft also hits the y-brace with the front left axle pushed up.....is this normal? Everything's built the way the book says...super easy! Just don't understand why there's so much interference up front especially with the axle articulated (left up) as everything hits????

Thanks all for any help!

PICTURES HELP 1000000 time better then specking

[XFITCRAWLER]

I can't even figure out how to build a rockcrawler kit and now you want me to try and figure out pictures......you're really testing my tech abilities now! Cool, let me get some up! Thanks for the help in advance!

Chris

[DonnieB]

I trimmed the x member as well......I also changed my link lengths....

[XFITCRAWLER]

Originally Posted by DonnieB

I trimmed the x member as well......I also changed my link lengths....

How do you change the link lengths? On the stock ones, there's no adjustment right? Looks like you just screw the black eyelets all the way into the aluminum link and tighten?

[XFITCRAWLER]

So, this first one is with the right axle pushed up....half stroke and it hits the left servo mount on frame!



This one is the driveshaft hitting the y-brace with the left side articulated up!



This one you can see that even with the wheels turned, it hits the entire length of the crossmember...entire range of servo steering!




This last one you can really see how the steering linkage hits the frame when wheels turned left and at only half stroke of shock shaft!

Thanks for looking at these guys!
Chris

[05Fronty4x]

You need to mount the link on the furthest hole on the horn, not only will this lower the link, but the steering will reach full throw sooner so the servo won't have to swing so far, which also keeps the link lower. Try to get it set up so the drag link (short one) stays as parallel as possible to the tie rod (long one) to both gain clearance and increase steering performance. If moving the link to the outermost hole on the horn doesn't lower it enough, try one of the bent rod-ends.

Here's mine before I switched to a longer Axial aluminum servo horn. you can see I had to trim the servo mounts as well since they were hitting the frame rails during articulation.

[XFITCRAWLER]

Originally Posted by 05Fronty4x

You need to mount the link on the furthest hole on the horn, not only will this lower the link, but the steering will reach full throw sooner so the servo won't have to swing so far, which also keeps the link lower. Try to get it set up so the drag link (short one) stays as parallel as possible to the tie rod (long one) to both gain clearance and increase steering performance. If moving the link to the outermost hole on the horn doesn't lower it enough, try one of the bent rod-ends.

Here's mine before I switched to a longer Axial aluminum servo horn. you can see I had to trim the servo mounts as well since they were hitting the frame rails during articulation.

Thanks....that's awesome! Cool, one fix outta the way. What exact servo arm is the one I need by axial......is there different ones?

[05Fronty4x]

I use Axial's aluminum clamping servo horns. You don't absolutely need it, but having a clamping style horn is nice because you don't have to worry about it coming loose, which the blue one above happened to do no matter how much I tightened the screw. The outer hole on the Axial horn happened to be a couple mm further out than the blue one there so I was able to go back to a straight rod end. Your drag link geometry is probably a lot better after you moved the link to the outside hole. Mounting it further away increases your steering throw, so be sure your servo isn't binding when you turn. If it is dial back your end-point adjustments (EPA) on your transmitter if you have them until it no longer binds.

[XFITCRAWLER]

Originally Posted by 05Fronty4x

I use Axial's aluminum clamping servo horns. You don't absolutely need it, but having a clamping style horn is nice because you don't have to worry about it coming loose, which the blue one above happened to do no matter how much I tightened the screw. The outer hole on the Axial horn happened to be a couple mm further out than the blue one there so I was able to go back to a straight rod end. Your drag link geometry is probably a lot better after you moved the link to the outside hole. Mounting it further away increases your steering throw, so be sure your servo isn't binding when you turn. If it is dial back your end-point adjustments (EPA) on your transmitter if you have them until it no longer binds.

Awesome.....Thanks for the help! What about the servo itself binding though? Any ideas on the servo horn hitting the crossmember (even though I already shaved the mounts and moved servo back)? Maybe I can notch the servo plate (3 holes) and slide it closer to the passenger side?

[05Fronty4x]

From your pictures it looks like your horn clears it, but the mounting tabs on the servo are hitting your frame. I didn't have that issue, only the servo mounts themselves were hitting. Does it clear the passenger side frame rail completely during opposite articulation? If it does and you haven't already done so, loosen the 4 screws holding the servo and push it towards the passenger side since there is usually a bit of wiggle room there. Also, one of the holes in the plate is slotted. If you slide that servo mount outwards a little it should give you more room to push the servo to the passenger side.

I wish I had more photos for comparison, but since that one I posted I have put on some high-steer knuckles which forced my to redo my steering links. I've also lengthened my wheelbase more and use different shocks that happen to be limited in up-travel quite a bit, so full articulation doesn't pose any clearance issues. Needless to say, the geometry of my steering and position of my front axle as well as travel doesn't resemble a stock scx10 at all anymore. That said, most or all that have taken the bumpstops off the stock shocks have had to deal with the clearance issues you are having and usually comes down to trimming what needs to be trimmed.

[project_mayhem]

The best way to fix the clearance issues is to remove the frame crossmember to keep the steering link end from hitting it. Instead of using a longer servo horn, use a longer steering link, and flip your servo so the link goes across the front of the servo. This decreases the link angle, and also allows you to put a bend in it, eliminating contact without using a longer horn. The longer horn is easier, but you lose a lot of affective torque. This is fine if you are running 300oz+ torque servo, but you aren't. You should always aim to use as short of a horn as possible. By possible, I mean the servo arm should come close to pointing directly at the steering knuckle at full throw. The only exception to this rule, is in a CMS setup. You miss out on massive exponential torque gains by using a servo horn that is longer than optimal. I run a stock axial servo in mine, and it has more than enough power to steer in every condition.

If you want to eliminate all the rubbing and contact, a chassis mounted servo is the way to go.

[XFITCRAWLER]

Originally Posted by 05Fronty4x

From your pictures it looks like your horn clears it, but the mounting tabs on the servo are hitting your frame. I didn't have that issue, only the servo mounts themselves were hitting. Does it clear the passenger side frame rail completely during opposite articulation? If it does and you haven't already done so, loosen the 4 screws holding the servo and push it towards the passenger side since there is usually a bit of wiggle room there. Also, one of the holes in the plate is slotted. If you slide that servo mount outwards a little it should give you more room to push the servo to the passenger side.

I wish I had more photos for comparison, but since that one I posted I have put on some high-steer knuckles which forced my to redo my steering links. I've also lengthened my wheelbase more and use different shocks that happen to be limited in up-travel quite a bit, so full articulation doesn't pose any clearance issues. Needless to say, the geometry of my steering and position of my front axle as well as travel doesn't resemble a stock scx10 at all anymore. That said, most or all that have taken the bumpstops off the stock shocks have had to deal with the clearance issues you are having and usually comes down to trimming what needs to be trimmed.

Yes, I did see that the one hole was slotted on the plate and that is definitely my next step.....like you said, it's just trim what's needed to make it work...gotta pay to play I guess! Thanks for the info!

[XFITCRAWLER]

Originally Posted by project_mayhem

The best way to fix the clearance issues is to remove the frame crossmember to keep the steering link end from hitting it. Instead of using a longer servo horn, use a longer steering link, and flip your servo so the link goes across the front of the servo. This decreases the link angle, and also allows you to put a bend in it, eliminating contact without using a longer horn. The longer horn is easier, but you lose a lot of affective torque. This is fine if you are running 300oz+ torque servo, but you aren't. You should always aim to use as short of a horn as possible. By possible, I mean the servo arm should come close to pointing directly at the steering knuckle at full throw. The only exception to this rule, is in a CMS setup. You miss out on massive exponential torque gains by using a servo horn that is longer than optimal. I run a stock axial servo in mine, and it has more than enough power to steer in every condition.

If you want to eliminate all the rubbing and contact, a chassis mounted servo is the way to go.

Great info!!! Do you have a recommendation for the longer steering link? A certain part number since I'm a newbie....wouldn't even know where to begin??