What makes the biggest difference?
 

I've got an axial scorpion RTC and am new to crawling and am trying to make the improvements that make the biggest difference.

So far I've replaced the stock ESC as it had no drag brake (used a tekin FX-R)
Ivented the rims and added wheel weight.
Those couple of changes have made a big difference.

Next on the list is behind the axle steering with axial's kit - the tie rod on the RTC is plastic and flexes and Iwant to get the battery off the high tray and this also gets more clearance than just higher knuckles and for a total cost of $43 just seemed the best bang for the buck. I've also got high clearance links fomring for the rear.

Iplan to go 3S lipo (a costly upgrade for a couple of batts and a charger) but to prepare Ihave some integy driveshafts coming. I'll likely regear once iget the battery setup. And a hi torque servo is on the eventual list as well.

So...tires I hear make a bid difference. Other than seeing what folks run at the local course (real rock set up inside a basement) what works well?

I've read bits about reducing the amount of articulation as being a good thing?Why would that be?
I've read bits about going 4 link, perhaps just in the rear over the stock 3 link. What's the advantage of this?
I've read bits about overdriving the front axle and understand why it's done - how big a difference does it make and are there any tradeoffs?

RE: What makes the biggest difference?
 

Have you seen or heard anything about HPI rock grabber tires? Very good, I use them on my comp, and they grip well, and help it climb steep inclines, even wet.

You reduce articulation, to prevent the chassis from getting "bound" by having too much. When a chassis gets bound, the motor spends it's time keeping it that way, not moving forward, or doing what it's supposed to do.
Overdrive is beneficial, but only on MOA chassis. It keeps a bit of "tension" between front and rear wheels, effectively "clamping" it to rocks, but as specified, can only be done to MOA crawlers, because it requires a gearing change. MOA chassis have two motors, hence two pinion gears. The front pinion gear must be changed to the next higher count (Ex; from 14T to 15T) or the rear to the next lower (Ex: from 14T to 13T) It cannot be done on the Axial, because the Axial has a central gearbox, and only one motor and pinion gear.

Nope, no tradeoffs, if you have an MOA chassis.

RE: What makes the biggest difference?
 

You can overdrive the axial ax10 - it has a front and read diff and they offer difference gear ratios. Perhaps you're thinking of dig where you can run the front/rear axle at different speeds to keep from having the back push the front too much on a very steep incline (it may offer other advantages but that's teh gist i get from dig)

your description of clamping it to the rocks makes perfect sense. best explanation I've seen yet.

RE: What makes the biggest difference?
 

Axial offers different ratios for their diffs now? I've been out of it for a while.........In that case, yes, overdrive would be beneficial, then!

The dig is only good for certain applications, whereas overdrive is constant, dig helps in tight turns (burn turns).

I'm glad to see someone actually thinking before just buying option parts willy-nilly, not knowing what they are after.

You're on the right track! :D

RE: What makes the biggest difference?
 

I've got a comp crawler, and here's what I found. Go with the HB rovers. Can't beat em'. Been to many comps where everything from ax-10s, to xr 10s, losis, and bergs- most of which were running the rovers. I'm also running the hobbico cs170 for steering in all my rigs. Surprising to note how many guys were running that same servo as well. It'll get warm (or hot)- but haven't burned one up yet. Otherwise, limiting articulation keeps your rig from following the rocks too closely. It's the difference between falling into a crevace, and floating over it with a wheel in the air. If you plan to compete, it's a must. If you don't, its not. I don't use antenna or fuel tubing- though I know many guys who do with good results. I just go with much stiffer springs to get the same effect. More so in the rear than the front- takes care of the torque twist problem that is so prevalent in non moa rigs as well. Hope this helps

RE: What makes the biggest difference?
 

Heheh! I went with the HPI Rock Grabbers, because they were the tallest tires I could find at the time, though now, I don't know. HBRovers are very good!Don't they come in that super-soft compound made for cold climes? Never had a chance to try them, and I'm not competing, or bashing crawlers, anymore.

RE: What makes the biggest difference?
 

went to the local course today and wow- they've got some serious friggin rocks there. Unreal.

A guy gave me a set of panther cougars and wow, much softer tires and that made a big difference. I also bought a chassis for parts - a but more patience on my part and I could have saved a few bucks on stuff that's on the way, but oh well - live and learn Impatience rarely pays off.

Anyway, with it I got a pair of alum hi rise links and installed them - the delrin that comes on the rtc/rtr has it's advantages I suppose, but 10 minutes into crawling and I got to watch my right rear one bend like a wet noodle when the front tire got a big jammed up - they are not strong enough. I have hi rise delrin ones coming I'll put on the front at least.

The stock servo is a tad weak but I have something on the way to remedy that. I had many issues with the front drag link catching on rocks but again, a fix is in the mail (BTA steering). My biggest issue was too much weight up too high - a 7 cell nimh pack in the stock top location just isn't oging to cut it - again, lipo and front batt is on the way. I have a new skidplate coming to move the links in - that will help a bit too.

OK, so how to reduce chassis flex? Is it just more preload/stiffer springs? Four link or how it's placed? or??

RE: What makes the biggest difference?
 

You might want to limit your articulation a bit. Calculate how much you currently have, then bring it down to at least 45 degrees. Bending that link may have been caused by binding the suspension I spoke of....High rise aluminum links ARE strong enough, if the chassis is set up right.
I would give you tips on the mods you want to make, but if parts are on the way, cool.

Chassis flex? If all the chassis screws are tight, you are not experiencing flex there, but a direct effect of too much articulation. Again, reduce your articulation, and the problem will disappear.

Your Axial, if it is stock, needs the upper links at the axle (which are mounted to a single point at the axle) to be mounted individually. Some buy four-link plates, some drill out holes in the front and rear servo plate, and mount each link to separate holes.

I myself, made a quasi-four link by attaching an aluminum shock rod end to the three link mount on the axle, and attaching the upper links to the shock rod end, so all four links move independently. That is the difference between the three and four link designs. Three links make the two upper links essentially one, and the axle, when articulating, rotates on that one pivot point, or axis, whereas four links have all four links moving along their respective planes of movement, and reduce what is known as "axle swing", which can cause the rig (chassis) to move in unwanted directions, as the suspension articulates.
Also, four links pretty much require you to reduce articulation, so see where I'm going with this? :)

RE: What makes the biggest difference?
 

Yeah, articulation was what I meant, not flex.

I now 'get' why 4 links are better. Does that mean just rear or both?

I was thinking of playing around a bit with the rear (less stuff in the way) suspension. I looked at a losi nightcrawler and they are similar yet different - their lower links are nearly a triangle- 2 points apart on the axle and they meet on the skid plate in the center, then the upper links go from the axle to about midway up the side chassis plates...looks easy enough to do on an ax10 (if you have a spare skid plate to modify which I do and some thought on getting a bolt in there.

So you're saying replace the triangle upper link with 2 links - ok, how far apart on the axle should they mount? I say some today where they mounted beside eachother on the axle just about where the triangular deal screws in, so other than being alum over delrin I don't see much improvement there ...  I assume the objective is to keep the axle parallel to the chassis through all movements? Wouldn't adding an upper link that mirrors the lower link do that? (just thinking out loud here)  I'm thinking that would work but would limit articulation - the compromise/trade off is you get a straight axle or articulation - to get more of one you lose some of the other?

RE: What makes the biggest difference?
 

As far as 4 links go, you would want both ends the same. The upper links don't have to be spaced too far apart at the axle, maybe 1/2 inch. I've seen some as far apart as one inch, but it's up to you.

Yah, you want that dual triangulation, otherwise the crawler would turn of it's own accord, when it articulated, without even turning the wheels! NOT a good situation!

On the skid plate....see the three holes at each corner? You want to cut a notch at all four corners, so the link rod end will clear the plate, and attach the lower links directly to the side frame plates with a bolt and nut. That will put the lowerlinks on the inside of the chassis! :)

3-links act as kind ofa pendulum. The upper link acts as a pivot, and the lower links and axle "swing" from the upper link, causing axle swing when the suspension articulates. Four links swing centrally, like when you rotate your wrist. That is the best way, because the axle won't affect the way the chassis acts. 3-links do, as the driveshaft position "swings", from side to side, when it articulates.

Reducing the articulation will make the crawler crawl better, believe me. I have seen crawlers do gangbusters with as little as 38 degrees of articulation! My own comp rig has only 42 degrees, and if you saw it crawl, you would be an instant believer! :) Axial makes rubber stops for their shocks, or you can cut pieces of the proper size fuel tubing, to make travel limiters, to reduce articulation.

RE: What makes the biggest difference?
 

Oh, BTW, jado6 is correct about the shock springs. Find the softest springs for the front, that will keep the chassis suspended, and springs at least twice to three times stiffer for the rear.

That, coupled with a four-link suspension, and limited articulation will give you an excellent handling crawler! :D