Micro Racer's 6x6 Build

[micro racer]

After finding several strokes of inspiration (GTA V Barracks Semi , Sczerba's multi-axle builds , and primarily the DMG's wrecker) I have decided to try and build something with a little more custom work than bolting on parts. I figured that a multi-axle would be a good place to start because of the lack of OEM support. Since I will be building with the budget and skills of a high-schooler, there will be no fancy custom machining or amazing tube work; there will only be parts that can be made with some saws, drills, and (almost) precision measurements. Okay, I can have my dad weld a few things, I can make my own links, but I won't be going crazy with this.

My "grand vision" for this build will be a mostly-scale-but-still-performance recovery rig. This basically means that it will have a hard body (scale) but no leaf springs (performance). For the cab it will use a Tamiya Knight Hauler body with the roof filled in. I will have a flatbed in the back, but with a roll cage/spare tire rack behind the cab. The main feature will be a KMS K2 or K3 winch going out the back of the truck. It will ride on RC4WD Yota 2 axles, have an SCX10 transmission, and will be powered by "A Brushless Motor" (very specific ; haven't decided what).

So far, I have most of the cab parts and the two rear axles, but that is it. I will have some more assorted parts this week, but I won't really start fabricating anything until next weekend.



Sorry for the long introduction, but at least I have an idea/outline that I can be held accountable to...

[micro racer]

Well, I went to Home Depot today and bought some 1/2" square steel tube for my frame rails. I have two 3 foot long tubes, but I only expect the rig to be about 2 feet long. While I was there, I also picked up some 8-32 all thread for when I am ready to do my links. Unfortunately, I will need the front axle and K44 4-link mounts for all of the axles before I can even think about the links...

[micro racer]

As I had nothing better to do today, I visited several hobby shops in San Diego in the hopes of finding the K44 link mounts. Unfortunately, none were to be found. On the bright side, I found many other goodies that will be helpful eventually.

First, two pairs of Old Man Emu 70mm shocks. I still need two more pairs for the front axle; I will be running a dual shock setup in the front.



If you couldn't tell from what the shocks were lying on, I also found some RC4WD 1/10 scale diamond plate. I threw away the label already, but it comes in two sheets of I think 8.5"x11" (size of a piece of paper). I won't really need this until I start the flatbed (not in the near future), but at least I won't have to go hunting for some when that time comes.



(I will cut the diamond plate down to the width of the body so it isn't huge.)

I also picked up three packages of Revo rod ends in preparation of link building.

In lieu of suspension work, I will probably start working on the body. The biggest thing I need to do is close the roof, but I don't just want to slap a piece of styrene on it and call it a day. While browsing hobby shops, I found some textured styrene for model railroad buildings. I think I will try to find a sheet that has notches about half an inch apart to make the roof not boring.

Mock up with what I am trying to go for:



Anyway, let me know what you guys think; I am open to questions, suggestions, criticisms, etc.

[BMoreScale]

Looks like a good start so far. What size wheels and tires are you planning to use?

[micro racer]

Thanks for the encouragement BMoreScale!

I will be using Gearhead Ute 1.55 wheels but I haven't quite decided on tires. The Baja MTZ's are good for their size at 3.25" but don't come in the X2SS compound. The Dick Cepek Fun Country tires come in X2SS but are 3.75" tall (I can still fit them in the wheel wells) and are not really the look I am going for (artsy sidewall). Pitbull Growlers and Baja Claws (4.19" and 4.5" respectively) are an option, but I need to get a size comparison first (Axial Ripsaws are about the same size). I can fit almost any tire under the flatbed (no surprises there), but I need my front axle to arrive so I can check clearances with the front fenders.

Like I said in the introductory post, this will be a scale rig that performs fairly well. This means that the RC4WD Rock Crusher and Stomper tires are both out, even though they would fit a recovery rig pretty well.

Whatever tire I choose, I will need (unfortunately for my wallet) 4 pairs. 3 pairs for driving on, and one more for two spares. This also applies to the wheels, which conveniently come in sets of 4 (2 sets needed).

On a slightly unrelated note, do you guys think my frame rails are too far apart? (I am sorry to pain you all with a vertical picture, but it had to happen...)

[micro racer]

Well, I finally have a got started on the cab this past weekend. I began by sanding down all of the nubs and ribs on the roof, then glued a roughly shaped piece of styrene to it.



I left the cab to cure overnight, then sanded the edges of the styrene flush with the body. I also decided to liven up the roof with some ribs/strakes/stripes.





I can't do anything else with it until next weekend, but my dad is helping me cut the square tube in half to make c-channel. I really like the idea of boxed rails, but trying to keep the weight down is also a consideration. Since the tube is only about $5 at Home Depot, I figured why not try it.

In the mean time, I am still ordering stuff to add to my Parts-for-the-Build box. My tires should be here by Wednesday along with the spring sets for the shocks. My front axle also came in last Wednesday.

Unfortunately, and somewhat inevitably, I have begun to run into some problems. First, the front yota II axles don't have lower shock mounting points, only on top of the axle. This causes me to have to rethink my front suspension in order to keep a level ride height. My second (and continuing) problem is that the link mounts are still out of stock at RPP! This really is only delaying setting up my suspension; it isn't actually a huge problem. Third, the shock boots I wanted to use are designed a "one size fits all" for the Old Man Emu shocks, but were obviously designed for the 90mm versions. This means that they don't fit very well onto my 70mm. I guess I won't have shock boots, but they are only an accessory...

Anyway, let me know what you guys thinks!

[micro racer]

Well, I haven't got to build anything onto my truck... However, I have still been working on it. After consulting the forums and some people at the LHS, I have determined that my truck will be powered by a ROC 412 1200kv with a 3s lipo. With that kind of power, the stock SCX10 transmission will probably explode in short order... To keep it from exploding, I am building it piece by piece with a Robinson one piece bottom gear, a Robinson idler, and a 32 pitch pinion and spur. I don't need a Vanquish case and a full set of Axial hardened gears are a bit expensive. In short, it is as bulletproof as I want to spend.

Anyway, this isn't too much and I hope to have something more interesting by next week (ie pictures), but we'll see.

[micro racer]

Unfortunately, this is week of building has not gone too smoothly. While I did get my 4 link mounts mounted and my motor did arrive, I had a few issues with my Gearhead UTE 1.55 wheels as well as my piece-by-piece transmission.

There were actually two problems with the wheels: one was jusg an annoyance but the other is a bit of an issue. The annoyance was simply me not having the right tools. Since I don't have a 1/4" drive .05" hex bit, I had to put all 8 wheels together with the good old L-wrench... My second issue is with the design of the wheel hubs. The hole in the center is drilled out to almost clear an M4 locknut. You know, the standard size that everyone uses?! The nut is literally holding on by the very ends of the corners! I will be solving this with some flanged lock nuts, but this shouldn't have even been an issue.

My other major issue is the transmission. Specifically, the 4 different ways that Axial manuals tell how to build the 32 pitch, dual plate slipper clutch. In the Scx10 Deadbolt, Scx10 Falken G6, Scx10 Power Wagon, and Wraith Spawn, the slipper assembly is built different ways in each vehicle. I initially followed the Deadbolt manual, but found that it calls for a random spacer that does absolutely nothing. The spacer is in place of the cone shaped spacer that comes with the new slipper shaft (AX31149); however, the spacer that comes with the shaft is defined as a different part number the same shaped spacer (AX31880, which is a nonexistant part number and really AX31180) in the Power Wagon manual. In short, not even Axial knows how to assemble this thing, and using the parts called out in the manuals gives a spur gear locked up by the spur gear cover . By the way, the slipper shaft in the Spawn manual (AX3019 won't even work with the new slipper plates; it is the old one without any flat spots...

I will probably e-mail Axial tomorrow and ask how and why their manuals incorrectly build the same slipper 4 times... In the mean time, I will continue to stare at the transmission and fight the urge to hit it with a hammer (that always helps, right?). I hope I have better luck when I begin to figure out my links...

(I have taken some pictures, but I am too grumpy/angry/annoyed to format them in Photobucket in order to post them).

[KMS]

The K2 SW180 holds the most line if that helps you any ,,RPPHOBBIES,, should have a few in stock. Robert

[micro racer]

Originally Posted by KMS

The K2 SW180 holds the most line if that helps you any ,,RPPHOBBIES,, should have a few in stock. Robert

Thanks for the recommendation KMS! I will be looking for maximum pulling power, so I will probably go with the 220oz K2. Will I lose much room for the winch line with that instead of the 180oz?

I have some beadlocks and tires to post pictures of, but it is a bit late to format the pictures right now... Tomorrow then!!

[micro racer]

Okay, I didn't post "tomorrow," but oh well...

I guess that I will start with the wheels and tires... (Sorry about the fuzzy pics, I don't really know what happened)



(Wheel picture lost to the Photobucket changeover, but I'm running 1.55 Gearhead UTE wheels)

Next, mocking up the ride height. It won't sit how it is in the picture; I have since changed how I want to do the rear suspension which influences the rest of the chassis.



I got bored while staring at the setup in the previous picture (trying to determine if it looked right), so I grabbed the front axle and quickly made up a tie rod and drag link. The drag link isn't finished because I haven't even built a chassis built to test fit the servo...



Since this isn't supposed to be a full flat bed or anything, the wheelbase will be a bit shorter than would be scale. The center axle will sit so the tire is about one inch behind the cab (about 15-16 inches). Therefore, the rear-most axle will be another five inches back, or at 19-20 inches from the front axle.





Thoroughly annoyed by Axial's manuals (still), I have decided to forgo the spur gear cover and just use the optional aluminum spacers. I am convinced that the cover for the new slipper assembly is different from the one I have and is called for in the manual. Anyway, no cover for me which is not really a big deal.

Fancy-SHINY motor and transmission:



In the mean time, I will try to get the chassis going real soon. For the sake of this build thread as well as for just keeping the project going...

[micro racer]

I haven't been able to work on the chassis at all, save taking some measurements and estimations. However, I did manage to cut up some aluminum for side plates. Since the chassis will sit almost at the top of the tires, I needed to drop it down to get remotely reasonable driveline angles. I also decided to completely get rid of the spur gear cover for two reasons: first, I got very annoyed trying to mess with it and get it to fit properly (which I never could do); second, the cover would have required me to mount the transmission even lower on the chassis than I already will have to.



Conveniently, the transmission has just the right shape to allow it to be mounted just between the frame rails without any spacers. The motor side is a bit tight, and I probably won't be able to gear up much beyond my 10 tooth pinion. I actually had to rotate the motor so the outside tab didn't hit the frame. In the end, the skid plate sits only about 1.5" below the frame...



You can see how well the frame keys in to the transmission.



I know this still isn't much, but I haven't really had much time to work on this. However, I can still figure out what I will need in the future. Once I get the chassis built and the suspension done, the next things I will need are drive shafts. Since the first wheelbase will be between 15-16 inches, I need will need either really long drive shafts, or a pass-through transfer case in towards the back. I will also want to get the servo mount integrated when I build the chassis, so I will probably need a servo to get measurements from...

As always, I am welcome to any questions, comments, or suggestions!

[micro racer]

Time to get this build thread all caught up!! I don't really know what to start with, since I have a bunch of new stuff to share! Also, I am super excited that I almost have this truck (mainly just the chassis; body isn't nearly done) under its own power! Anyway, on with the new!

First, electronics rats' nest...



I will be running the pretty much obligatory Mamba Max Pro, a Spektrum S6100 servo, a CC BEC set to 7.4 volts straight to the servo, a Spektrum SR410 receiver, and of course the Tekin ROC 412 1800kv. The Mamba Max is mostly self-explanatory: sensored brushless, endlessly tunable with a Castle link, and capable of handling lots of power. The BEC is also pretty obvious... I know Hitec is the go-to servo manufacturer around these parts, but I figured it couldn't really hurt to try something else. With an extra ~30oz/in (I know, it isn't that much of a difference) compared to a 7955 for the same price, the S6100 seemed like a good choice. The Spektrum radio system is because that is what I am running in everything else. I haven't had any issues so far, unlike my first radio, a Futaba 3PRKA...

Back on topic then... We all know that these trucks don't just run on magic, right? Maybe the magic smoke that shouldn't be released from ESC's and stuff, but whatever...

Since this is a fairly heavy truck, a low Kv motor, high cell count, and high capacity seemed obvious. Unfortunately, my charger tops out at 50 watts, or about 4.5 amps for a 3s lipo (I wanted to run at least a 5000mah with the 20c discharge rate). Thus, I ended up with Dynamite 3s 4000mah 20c lipos .



I am very aware of the low c-rating and will monitor that while driving. With a brushed motor, I know that crawlers don't pull that much power. However, I am using 3s brushless in a ~12 pound or so 6x6 recovery truck. I will try a single battery setup for a while, but go to parallel if I have any issues.

After electronics, I have figured out my driveshaft issue. I will be using T-maxx 2.5 driveshafts and yokes, and (what I think are) Slash driveshafts and yokes. The maxx shafts are directly from the transmission, and the Slash shaft goes from the center axle to the rear. I would have used a cut down maxx shaft for the center to rear, but the yokes were so long that there was only about 3/8" of the driveshaft engaged. Slash yokes are slightly smaller, allowing about an inch of engagement.

T-maxx yokes are really big, both in length and diameter; it just clears the spur gear.



Third, the spaghetti! No, not the electronics; the electronics are a rat's nest (as mentioned earlier). I am talking about the suspension links...

As I have no access to a lathe or any such machining tools, all-thread, stainless brake line, and Revo ends are as "fancy" as my links will get.







I have absolutely no experience designing suspensions, so I figured an "oops, that's wrong" hole would be good to incorporate into the middle plate. (Just choose top or bottom and go from there...)



I had a few... issues... while drilling and tapping my frame for suspension mounting...



In case you can't see why the hole isn't a hole, there is a broken tap stuck in it... Fortunately, I managed to fix all blocked holes (the tap broke three times) and I don't have any unused "mystery holes.

For the finale (of this post ), I give you a CHASSIS!! (Ignore my over-excitement; I have my reason that will be explained shortly...)





If you missed it in an earlier post, the frame is 1/2" square steel tube. It is braced in the front and back, with extra braces/floor-pan mounts across the middle. Now, this is exciting, for me at least, because I had no idea how to weld before last weekend! That's right, my dad taught me how to MIG weld for my first custom chassis! Granted, there was a lot of spatter and "oops, that didn't even join anything," but it was fun. In my personal opinion (which means squat), I think it still turned out pretty well... with a judicious amount of grinding away excesses and "errors."

Anyway, the suspension is basically complete, save some sleeveing and front shocks; the electronics are all ready to go in; and the body just needs a little more sanding and primer before painting (and an out-of-stock Tamiya grill).

I can't wait to get this thing running! Then I can finish up the bed and accessories...

Thanks for letting me dump out all of this, and make sure to post any questions, comments, or suggestions!

[micro racer]

Oh, something that I forgot... Pictures as it currently sits:





Also, I ended up going with about a 14-14.5" wheelbase; it just looked better to me....

[golfmech]

Awesome build keep the pics coming. And congrats on learning how to weld.

[micro racer]

Thanks Golfmech! I hope to get this running by next week; Spring Break!!

[micro racer]

I don't have any real updates yet, other than to say that this behemoth is running! I must say, it is faster than I expected; even with the approximately 5.6:1 gear ratio, it is just a little faster than a box stock SCX10. I will try and post a video, but don't get your hopes up...

No pictures right now, but expect them in the next few days (probably the weekend).

[micro racer]

Oh boy!! Lots of updates today!

First, a video link that I hope works properly...

Sorry about the glare and fuzziness in some pictures... Please just deal with it...

Finishing up some chassis work, specifically the servo mount:





Steering is done...



Body hangs on by itself...



To all you scale builders who have to take out a bunch of screws to get your body off: Body clips, suckers!!





For mounting the rear of the body, I intended to use body clips like the front (middle). However, the addition of gas tanks to the area will make using clips extraordinarily difficult. I will just modify my original mounts, servo mounts, by bolting them to the floorpan (instead of using clips) and using pins to hold the back. The pins will be hidden (mostly) by a roll cage and a pair of spare tires.



Just a driveshaft set-pin threaded backwards into the servo mount and poking through the body. The servo mounts were originally to be bolted in this exact same spot, I just exchanged screws for pins (hope this makes sense).



Here are the electronics mounted. I still need to mess with the wiring, shortening and routing.



Fake fuel tanks are mounted directly to the chassis underneath the floorpan.



Painting the roof and protecting the rest of the paint with a trash bag...



Ta-da! The body is all painted! I am just waiting on a few accessories that are currently en-route, most importantly the grill... (Random Du-Bro packaging to help my camera figure out colors)



The body accessorized a bit and mounted:



Finally, the rudimentary beginnings of a rear bumper.



Time for a little wrap-up:

Almost all of my running gear is together, as made obvious by the video (if it worked), however, I am still several pieces away from completion. I still need to get both winches (front and rear) and a winch controller. I need to pick up my LED's and check on a light controller, then get it all put together. The rear roll cage and bed needs to be fabricated. The body still is missing a few pieces and mounting needs to be worked on.

That's all for now! Let me know what you guys think!!

[Szczerba]

Looks good. And nice work on a correctly setup subframe suspension setup.

[micro racer]

Originally Posted by Szczerba

Looks good. And nice work on a correctly setup subframe suspension setup.

Thanks Szczerba! Honestly, I had no idea how to "properly" do any of the suspension, except for not linking the center and rear axles together...

I tried to search for some advice on geometry, but nothing came up. I wish that there was a bit more triangulation in the lowers, which are basically parallel, but the overall stiffness of the links and chassis seem to keep the axles aligned well.