BTA Steering Link Mod for Axial Crawler

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Timmahh

RCNT Addict
Messages
729
Location
Tri City area Michigan
RC Driving Style
Bashing, Racing
durring my Mock up of some stuff for my Moon Buggy build, I worked out a pretty simple way to do a BTA Steering setup for the Axial AX 10 rigs. It works very well, is free moving, and should work with most any Axial setup. stock chasis or tuber, or pretty much any scaler setup as well that uses the Axial front axle setup.

what you will need besides the 2 stock steering linkages (long and short) are:

2 small link/end spacers, approximatly 2mm each for your long link,
4 bent link ends (one bends downward, and three that bend to the side).
2 3mm spacers for linkage clearace (raises linkage up off knuckle arms to is clears pinion shat at center of axle)
2 bolts, 1 approx 22mm long, one apporx 16mm long to mount links/spacers to knuckles.
4 link rod pieces (threaded rod for link/ends to thread to).

start by taking your long link, and install 2 angled linkends that are the to the side ends. before putting the end on the link, place one spacer (1.5mm to 2mm) between the link and the end and tighten end to link. do this to both ends. position both ends with angle to the same direction. (spacer size my varry a tad, your looking to get nuetral toe, or even 1 or 2 degree toe in. without spacers, you have around 3* toe out each side when mounted on the inner most holes. using the outter holes causes the long link to interfer and ride the bottom shock spring retaining cap!!!!)

take your short link and install the 2 remaining angled ends, No spacers needed. you should have one end, with to the side angle, and one end with a bent end going at an upward angle.

now, install your knuckes with steering arms to the rear. take a long mounting bolt (20?mm), and push it thru the upward bent end on the short link, thru the stock steering spacer, thru the long link (with link moving in toward the pumpin, not out toward the chassis) then thru the 3mm spacer, and thread it into the inner most mounting hole on the arm knuckle.

use the shorter mounting (16mm?) bolt and thread thru the other end of the long link thru the 3mm spacer, and then into the inner most mounting hole on the opposite knuckle.

once installed and tightened, you should have free movement of your knuckles and long linkage up till the arm bumps your mounting tab, or axle if you have removed the outer most link/shock tab. you may see the linkage hitting the shock spring caps as it centers, but it should be Minimal and not cause much if any issue.

install your servo arm on the other end of the short link.

you ll want to zero your steering trims before installing your servo horn obviously, then retweek for center, and then EPAs.

you ll see in my pics i trimmed the outer most shock/link mounting tab off. this allows a far tighter turning radius. the inner mounting tab has the shock mounted toward the knuckles, and the bottom link mounted toward the pumpkin. has Great steering radius and the single tab should hold up well barring a 20 ft drop.

if you look, you ll also notice i used the Axial Clockable Cs, but they are mounted in stock position. one killer thing is they used allen set screws to hold the C to the axle, thus no screw head limiting turning radius, but you will hit the outter most mounting tab for the shock/link, which is why i further modified my front axle mounts by removing the outer most tab.

here are some guidance pics so you can see the orientation of the links and ends, in relationship to how they are situated once installed.

front on shot.
DSCN4892.gif


shot from behind on the right side
DSCN4893.gif


top body off
DSCN4894.gif


right side (top front view)
DSCN4895.gif


left side (top front view)
DSCN4896.gif


shockcap/link clearance shot
DSCN4897.gif


top view wheels straight.
DSCN4903.gif


top view wheels right
DSCN4902.gif


top vew wheels left
DSCN4901.gif


bottom view straight
DSCN4898.gif


bottom view right
DSCN4900.gif


bottom view left
DSCN4899.gif
 
Last edited:

Candyman

'Cuse is in the house!
Supporter
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6,858
Location
Syracuse, NY
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For us crawler-impaired hobbyists who may be interested in crawling eventually, can you explain to us in layman's terms what BTA steering is, what it does, and how it's different from standard steering? Thanks.
 

Timmahh

RCNT Addict
Messages
729
Location
Tri City area Michigan
RC Driving Style
Bashing, Racing
sure. BTA = Behind The Axle. If you look at most any stock Axial Crawler, you will see the steering linkages are out in front of your axle, and when moving forward, tend to take a beating, as well as cause you to dead stop when hitting a flat spot, and occasionally will move your rig side to side as you approach a climb line.

by moving the steering linkages behind the axle, you solve a few issues. no linkage interfering with your approach, either by hitting a flat spot and stoping you dead, hanging you up, or moving your rig via the linkages either sliding along the rock, or when you turn the wheel and rubbing agains the rock. so you gain very needed real estate infront of your front axle beteen the wheel. now what will hit the rocks will be the axle housing itself, which being angles, id much less apt to stop you dead, or really change your line, though it certainly can and still will as it slides over taller spots.
it also helps keep things in better condition cuz they are not being bashed into the rocks. lol

for comparrison, here is a pic of the same crawler above, but with the stock steering setup.
DSCN4645.gif

DSCN4649.gif



hth
 
Last edited:

Candyman

'Cuse is in the house!
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Messages
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Location
Syracuse, NY
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Perfectly clear now. I had never noticed that the stock setup left the linkages out front. Seems odd to do that in my eyes. Every other RC I've had has the steering linkages behind the axle line. Just seems natural that way. Seeing them out front looks just wrong. And I can see how moving them back behind the axles would help.

So from the looks of it, the biggest challenge in moving them back would be getting them to work around the front suspension links.
 
Last edited:

Timmahh

RCNT Addict
Messages
729
Location
Tri City area Michigan
RC Driving Style
Bashing, Racing
Exactly that Candyman, Real estate is Pretty Limited between the pumkin, links/ and shocks. I dicked with this setup for a few hrs, before i had it setup and working like it have it now.

i initially made a test attempt at mounting the shock on top of the axle, more out of the way, and i am still really looking at that as an option. will post more.

i should also mention ifyou look, i have re mounted my upper links on the chassis in a higher postion over stock. this has helped to even out the horizontal orientation with the lower links, but is a bit far foward, offering a bit of axle clocking of its own.
this am when i first ran, i had it clocked so much, when i turned, it looked like a road grader turning, you know with the overcambered angle when they turn. was kind of funny.
 

NCNitro

Fist of Goodness
Staff member
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18,561
Location
Central Florida
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The thing with that mod that would worry me is the fact you cut off one of the link mounting tabs on each side of the axle. I honestly don't see that one tab holding up too well.
 

Timmahh

RCNT Addict
Messages
729
Location
Tri City area Michigan
RC Driving Style
Bashing, Racing
you d be surprised how tough the plastic is. I've been running a Very similar setup on my scaler (using axial axle with one tab cut off) for a few months without issue.

and if i do have a problem with the tabs, then i ll either buy a new axle case for 9.00, or mod up a new mounting setup.

but ya, i hear ya, i too was wondering if the tab would hold up. Seems to be good though.
 

slowngreen

I got in your recliner.
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17,562
Location
IDAHO
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i hate to say it lol but the first time i did a stage 2 mod on mine i just cut one tab off each side instead of going on buying longer bolts and so did my buddy on his, neither one lasted more than 3 crawling runs, i broke both remaining tabs the second time out and he broke one the 3rd time out...
 

NCNitro

Fist of Goodness
Staff member
Messages
18,561
Location
Central Florida
RC Driving Style
Bashing, Racing
i hate to say it lol but the first time i did a stage 2 mod on mine i just cut one tab off each side instead of going on buying longer bolts and so did my buddy on his, neither one lasted more than 3 crawling runs, i broke both remaining tabs the second time out and he broke one the 3rd time out...
That's what I mean, I just dont see one tab holding up to the stress during crawling. you might get away with it for a scaler, but I wouldnt even chance it on a scaler either.
 

slowngreen

I got in your recliner.
Staff member
Messages
17,562
Location
IDAHO
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yeah i would go ahead and order some new axle housing to be ready for when it breaks....
 

Webbage

RCNT Addict
Messages
843
Location
United Kingdom
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Bashing
It's a good lookin' mod Timmah, my only concern is that steep angled servo link is gonna potentially loose you a good bit of side to side leverage as more of the force from the servo is pushing vertically than normal. Most guys try to get that link as flat to the track bar as possible as it is on the stock Axial steering for that reason.

Also the added vertical stress is gonna bend and maybe even sheer the tab on the steering knuckle at the wheel end. I think the guys already said you weakened them by trimming off the tabs you did and that's not gonna help either IMHO.

EDIT: scratch the second comment you put alloy knuckles on, and they meant the axle to lower link mounts, and FWIW I agree, using one single tab like that will sheer in no time because the tab will twist with the end of the link at the high articulation angles.

One other thing too though is you might find the servo start moving vertically because of the vertical stress from the link, shouldn't be a major issue unless you use a high-torque servo or metal mountings (in the later case thread-lock ought to get rid of any looseness).
 
Last edited:

Timmahh

RCNT Addict
Messages
729
Location
Tri City area Michigan
RC Driving Style
Bashing, Racing
I'm looking at a way to mount the servo horn to the bottom of the servo to make the idler arm more horizontal. it doesn't appear to to do much for down as the knuckles are are very smooth moving, with out any binding, so when the horn moves, the knuckles easily move sideways before moving downward.

maybe due to the smaller course i run on, opposed to the larger more natural coursed, that the one tab setup seems to be doing ok, even in hard articulation.
I've been wheel bound witht he scaler and pooped the drive shafts durring the bind up but it didnt seem to bother the knuckles or the tab. but time will tell as I've only had the chance to get one battery pack thru the setup currently. i know its not an Ideal setup, but to get my steering links out from in front, to me, would be worth some hassles with a weak tab. if/once it breaks, i ll just make up a new metal mount position and mount it on the axles.
 

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