The Maxx Project

[OSRC]

It's 2022, who the hell is building a Maxx crawler?

Me... Got a huge box of parts laying here collecting dust. Parts from my original, OG Pro .15 T-Maxx all the way through to my current 3905 E-Maxx. I've tried to sell the EMaxx a few times over the years but there was little interest, so it's been boxed up for years. I won a set of tires a decade ago here when there were giveaways, and the entire project is built around finally using the tires. And having some fun... Haven't done a build thread in ages so bear with me.

The entire reason for the build...using these bad boys. Won these in a Christmas giveaway, and they are huge. It took almost 9 years to find the Axial narrow 40 series beadlocks they are mounted on, but persistence pays off as I picked these up off a sale thread about a year ago. The RC4WD wheels were originally $300/set, ouch.


Joining the build in progress.... Aluminum bulkheads from my OGMaxx, wide arms and towers from the EMaxx, and a huge piece of aluminum. Wb is about 20" Forgive the mismatched screws and what not, everything is in mockup currently.


When your project is so big, you can draw your plans on it.


On the bottom, I cut a T-maxx aluminum brace in 1/2 and then spanned it with an aluminum skid. I filled in with some pieces of ABS to tie the center together. When it's all bolted up, it's so solid Ashford and Simpson sang a song about it. Boy, some 3D printing would have come in handy here, but I haven't mastered that skill yet, so saws, drills and files are the name of the game.



This will be using 4WS, it has to - the Maxx parts are not designed for crawler level steering. I initially tried 2 front bulkheads, but the caster was too severe in the back, so I reverted to the std. read bulkhead. I clearanced out a bit and stuffed another steering rack in the back. I did have to order another set of toe links, otherwise all the parts I dug out of my box.


Transmissions....I've got room for anything. Really, I have no idea how this is going to work, but they are laying here so I used an RC4WD AX2 up front, and a divorced Axial 3 Gear as a transfer case. I'm not sure how these gears are going to hold up, but 3 gear transmissions can be built pretty tough. Can easily swap over later to something heavier duty if needed. I do like this combo as it's relatively compact and the motor is up front and on the chassis. Time will tell. Thankfully, I have 5 and 6mm ends for the T-maxx shafts so adapting the Axial bits to the Maxx diffs is cake. Glad I had them, Not even sure I could track them down now.



The Tmaxx shafts are much smaller than the newer 3905 versions, but they work perfect - they just clear everything underneath....

[MaX-D]

This looks like a fun build. Anxious to watch the progress on this.

Sent from my SM-G991U using Tapatalk

[calcagno45]

Nice!! Anxious to see this progress. What body are you thinking?

[ferp420]

those 2 speed trans have a tendency to sheer the output shafts i would pick up a extra to have on hand ive sheered 3 stock ones myself all replaced with ssd shafts and i havent broken anything else on any of them since

[350TacoZilla]

Do you have a link to pics? google chrome has been giving me issue of not seeing pics unless I click the link and allow them basically due to a out of date security certificate or some BS...

[OSRC]

Originally Posted by calcagno45

Nice!! Anxious to see this progress. What body are you thinking?

Plenty of 1/5 bodies out there...I have one handy.

Originally Posted by ferp420

those 2 speed trans have a tendency to sheer the output shafts

So far, so good. This one has been doing duty in my 1/6 truck for years. If it breaks, it breaks.

Originally Posted by 350TacoZilla

Do you have a link to pics?

That's odd - I use Chrome exclusively and no issues. Link to gallery: https://postimg.cc/gallery/fZwm8D5

[OSRC]

Time to stat working on the driveline...planning on mostly stock for now until I get a roller. I'm sure I'll find a way to throw more $$ at it.


Opened the old style diff to try and cram in a new style locker - there's already one in there! I have zero recollection of ever buying an old style spool....oh well. Gears look great for a truck I bought 22 year ago (!) - re-greased it and bolted it back together.


Kind of stuck while I wait for parts. Steel trans gears for the t-case, hingepins, and a few other odds and ends.

[OSRC]

Making a little more progress...

Got the diff assemblies together, spools front and rear of course mixed and matched with gen1 and gen2 parts. I modified some V1 Maxx shafts for center shafts and they worked out perfect. I have no idea how they'll hold up strength-wise, might be some custom MIP's in my future. Axle shafts are stock Maxx v2/Revo, which are pretty darn strong. Not worried about those, though CVD's are most likely in my future. Proline pro steering components front and rear also - no idea how I ended up with 2 of them, but glad I did. I had 8 fancy shocks ready to go, but the stockers gave me more travel so I just bolted them back on.



I would have liked 32p gears here, but didn't have any handy...after messing around a bit, I found a mod6 gear from my old TLT fit perfect. Tougher than 48p anyway, but 32p gears are already in my cart. Gearing is currently 17/87 giving me a first gear ratio of 237:1 and a second gear of 84:1. I'm not sure how that will work out with 9" tires, but guess I'll find out.


Some more mock up... I drilled and tapped for a standard sized Enduro battery tray - I can mount it in a few different places to adjust weight balance.


Wide shot of the lower driveline... takes up my entire workbench!


While I had the upper chassis off, I did some trimming... added the servo cutouts, clearanced front and rear for the tires to turn and cleaned it up a bit. I'll add some cutouts later. Maybe.


Bolted back together....Love it when a plan comes together!


Testing the driveline with 3v power...smooth and strangely silent. Motor is a big brushed motor I picked up from Kershaw years ago...not sure what it is. Bigger than a 550 for sure, though the same diameter can. It's a 5 pole which is nice. I'll be running it on 3S for now - I don't think the driveline will handle 4S without some more beef. I'm not even sure It'll handle 3s!


I couldn't resist and had to bolt the tires on...Track width is about 18.5" ... I'm going to need some strong servos!

[Gula]

That's a cool platform to build off of. Your diffs may not last longer than the first outing though. I have a large build on wheels that are about 6 Dia or less (GRC pullers) and you can hear "that audible click" on rapid deceleration, or giving it too much go pedal. I think I won a set if the same tires many years back, they'll go on MF axles at 8" tall.

I found a few images of a servo mount that goes between the bulkheads with direct steering. Mine struggles with steering very badly due to servo saver.

The rest looks so "tiny" bolted to them tires. I'm intrigued by you not mentioning a body/brand..... New bright, Fastlane, Planet toys, Jada, Dub, RadioShack, what?

[OSRC]

Originally Posted by Gula

That's a cool platform to build off of. Your diffs may not last longer than the first outing though. I have a large build on wheels that are about 6 Dia or less (GRC pullers) and you can hear "that audible click" on rapid deceleration, or giving it too much go pedal. I think I won a set if the same tires many years back, they'll go on MF axles at 8" tall.

I found a few images of a servo mount that goes between the bulkheads with direct steering. Mine struggles with steering very badly due to servo saver.

The rest looks so "tiny" bolted to them tires. I'm intrigued by you not mentioning a body/brand..... New bright, Fastlane, Planet toys, Jada, Dub, RadioShack, what?

It is a cool platform, very easy to modify. I have to say the diff gears look mighty beefy on their own, but once I bolt those giant tires out there.... I don't know. I am amazed at how good that OG T-maxx gear looks, I put gallons on gallons of gas though that T-maxx - raced, bashed, jumped, and beaten. Not to mention a Pro .15, OS .18 and eventually a .21 conversion. They still look new 20 years later. Amazing. I did track down some hard machined option gears, so if things grenade I know I can at least upgrade.

I thought about doing a direct servo, but the geometry would have been a bit odd. Very Tamiya-esqe... Would have been easy enough to mount it between the chassis supports where the trans is, but I decided to stick with stock for now. I've got a plan kinda in mind to lock out the servo saver and beef things up, I suspect the steering is going to be very iffy. In fact, I don't think 1/10 servos are going to be up for it. BUT won't know until I try, right?

As far as the body, I've got an option or two here. Nothing fancy, I just haven't decided. Ironically, I wasn't planning it this way, but the wb matches the current 1/5 MAXX so there's plenty of options out there.

[calcagno45]

Those center shafts look loonnnnggg and ready to twist up like a spaghetti. Although keeping it on 3s might be ok unless you get all 4 tires jammed up. That motor looks like a 650 or 775 brushed. Kershaw offered a few different options as he tried to fit larger and larger brushed motors onto the Maxx transmissions.

Regarding diffs, if I recall, people were modifying the bulkheads slightly to fit Losi LST diffs in the Maxxes. Those were Like $30 a diff and were way beefier than stock Maxx diffs. But I think you’d need CVDs. The other option was the UE Supermaxx diffs for about $250 at the time. May be able to find a set on eBay now for outrageous prices. I’m sure you could find a thread on the Rc-monster.com forums.

Bought my first Emaxx back in 2005. Not to sound like a grandpa but those were the days. Guys we’re just breaking into brushless motors like Feigao, Hacker and Lehner. LiPos weren’t a thing so you had to build NiMh packs. I remember one guy running dual 32 cell NiMh packs on a twin BL setup for speed runs. I had a Schultz ESC and Feigao 9L motor on 14 NiMh cells and boy it was much quicker than those Titan brushed motors. And that was before Truggies were a thing so there was a Monster Truck class at most race tracks. But I digress…

[OSRC]

Finally got in some parts I've been waiting for... Tallest body mounts I could find and a few odds and ends.


Spent some time buttoning down the suspension. Everything was just mocked up so I went back in and went through both front and rear assemblies getting everything tight. I picked up a front skid plate for the rear and got the steering sorted out. I had a bit of binding on the bellcranks that a little dremel work took care of, and for some reason one of the rear knuckles was binding terribly. I took it apart and reassembled it and now it's fine. Not sure what was binding it up.


My Hwang Chang $22 trans showed up and I swapped over the input shaft from my home brew t-case. Spent some time shimming it out, it feels solid and it's all metal. My Axial t-case is pretty old, it still had plastic gears in it! Old style stronger ones, not the new crap that was coming out towards the end before Horizon stepped in.


Sitting in its new home...looks nice in there!


Picked up an HW 880 for ESC duties - should have no problems with that big motor and through in some 35kg/25kg servos just to get it moving. Zip tied everything for now.


Ready for a test run....My SCX24 is there just to give an idea of scale.


Test run: Motor and ESC feel fine actually, it moves around pretty good. I just rolled round the driveway but it is super torquey, especially in first gear. Should be fine out on the trail. The steering though? I knew the servos would struggle, but wow - I basically had no steering front or rear. The "35kg" up front made some suggestions as to which way the wheels should turn but the wheels just gave it the finger. The rear ties just did their own thing. The servo savers in the bellcranks were not doing me any favors either. Totally scrapping this steering plan, I have to go to plan B - That what testing is for!

1800+ oz of torque and aluminum adjustable bellcranks on the way!

[AK KRAWLER]

Originally Posted by OSRC

OSRC - That thing is a BEAST and I LOVE it!!!!
Looks like it should be super fun!

[Gula]

Hey, calcagno45, those days were the isht,, when kitbashing was the only way. That and full on custom, not these "kit" builds money just gets thrown at!


OSRC, I have similar issues with smaller tires than you. I can't imagine. Well if your diffs don't hold up and you do the Losi diff mod, let me know I'll print you the bulkhead to diff adapters. I recently did diff mods like that for two trucks. You can use maxx shafts on Losi diffs, if you take 4 of the stub axles off of the u joint. Cut threaded ends off, install in diff (losi) and attach traxxas cvds. May have to give it a shave. For your steering woes. The old t/e maxx aluminum bellcrank has no servo saver built in.

[OSRC]

It IS a beast! I just have to get it under control...

Thanks Gula, I'll keep that in mind. I suspect once I sort out the steering, weak links in the driveline will start to crop up. Those center shafts will probably fail before the ring and pinion do. IIRC, the original Maxx had the servo saver on the servo itself - I think I have the OG cranks here somewhere. I could not find any non-saver cranks online, just the newer style which is ok. The HR ones I bought are adjustable, and look fairly easy to lock out if needed.

I have no illusions about building a pro crawler out of this per-se, just building something for fun. Maybe a trail run or two and then I have a vague vision of a hitch and an adapter for my wagon and I'll put it to work during camping season hauling ice, firewood, etc. All my other crawlers are ready to go for the season and there's really nothing out there I want, so I'm digging in my stash for projects. Already rebuilt or restomodded some of my old Tamiyas and Kyoshos, and I'm running out of projects! I'm trying to do it on the cheap, though I've thrown about $300 at it already.

[OSRC]

While I'm waiting for the new servos, I decided to get the boy mounted. I had this Redcat body laying here, and it works out well with the WB. Ignore the hacked off front end, just cut off the bumper to get it mounted, I'll sort it out later. I do NOT like the Proline body mounts. Those big knobs are convenient, but they look like crap.


I would have preferred a buggy body of some type since I think it would have fit the independent suspension better, but the only one I liked was the Losi DBXL body, and it's $200! Heck no! So the Redcat it is. It looks ok to me, I'm not building a scaler here. And old HPI 5T body looked ok too, but was just a bit too long. The shock springs were just enough w/o the body, but even though the body is Lexan and fairly light for what it is, it's still a lot of plastic and it's weighing down the truck... new springs are a must. It's about at ride height in this pic, but if I push down on it, it stays down.

[calcagno45]

Man I think that body looks right. I’m sure a buggy body would look good but that one looks good.

Yep, original Max steering had the servo saver on the servo horn, a good ole Kimbrough 124 was common. So those original Maxx bellcranks should work better. Part number TRA4943 and Amain has them in stock.

[Gula]

The copper or gold AE MGT springs are the stiffest available iirc, maybe try those.

[OSRC]

I'm on a Maxx kick, I bought an old T-maxx to restore for fun, (and another for a smaller electric conversion) and while working on it I got a wild hair and decided to work on this project again....

Finally tore it all down and cut the chassis for the larger servos. When we last met this beast, it had 2 standard sized servos installed. Strong as they were, they didn't stand a chance of turning those huge tires. So I picked up 2 1/5 servos....not only are they stronger, but the bigger gears should hold up better with those big tires. Shown with a std. servo for reference.


Going to take a little trickery getting everything lined up, but it should work. I did have to trim the ears a bit and mount the servo above the chassis - it would not have lined up at all mounted on the bottom. The HR steering assembles went in as well, I used the heavy spring and cinched it way down. We'll see how it holds up.


Got all the linkages lined up, chassis back together, and added a project box to hold the receiver and BEC. with 2 large servos, a BEC was a must. It's set at 6v for now, but I can bump it up as needed, the servos take up to 8.4v. Want to see how they do before upping the voltage.


Buttoned up and ready to go.


Out in the sunshine for some testing. With the body on, the shocks don't stand a chance - firmer springs are needed for sure.



It goes fine, the motor seems to have plenty of power and the gearing is spot on in both gears but steering still needs some work. It tends to "clod" - aka the rear wheels do most of the steering. The servos didn't seem fazed at all, but the spring in the servo saver was crying uncle the whole time. Oddly, the rear steers much better in both forward and reverse, must have a slightly stronger spring. I cranked down on the front quite a bit and it helped but ultimately, I'm going to have to lose the springs and just sleeve it. .


Posing with the radio... I don't have a channel for the 2 speed, so I'll have to swap over to my GT5.


I'm re-thinking my body... It's either hack this one to pieces (it rubs up front terribly) or come up with something else. Really, it looks odd with a truck body, I'm thinking some sort of Buggy might look better with the suspension.


On a side note, I finally have a crawler big enough to drive up my steps to get outside... lol. Didn't have to carry a thing.

[Sweetride95]

Super cool man, I love watching the progress!