Torsion Maxx - Kira Krawler

[JamboreeTJ]

I posted this earlier on my old thread in the Newb section, but I'd like to see if some of you Maxx guys have some thoughts on the build-up. I probably should have just posted up in this section originally.

I've been working on the 2nd incarnation of the Kira Krawler (named after my daughter) over the last week or so. I'm converting it from 4WIS to a custom torsion chassis suspension.






These flex shots aren't quite fair because the 4WIS is still live. I'm waiting to get some links to lock out the A-Arms later this week. Still, I think I will get more flex out of it than the pics. I can twist it 90* now without too much trouble. :smt096




I still have to mount the receiver, finish rigging up the front steering, fab up some servo mounts, fab up the rear steer and figure out how to mount the body. I also have to trim that motor mount that is hanging down and make up some kind of transmission skid. Oh yeah, and mount the batteries.

I think I'd like to create a body mount over the motors - holding it at the roof of the cab. It is an HPI Rubicon Jeep body. We'll see how that works out.

Soon, I'll probably get some shorter bolts to mount the motor/trans without using the stock Maxx chassis brace at all. For now it works OK and helps protect the drive shafts.

Any thoughts or suggestions?

I have a set of Moabs on the way too.

[Toph]

Looks pretty good. But I say deffinatly get rid of the stock chassis brace. That will get hung up on rocks like a magnet. Also if you mount the tranny sideways you won't have it hanging out the bottom of the chassis. It is alaways best to try and keep everything from hanging out the bottom of the truck. Just a little seggustion.

[4xFord]

I think that looks like a really good start. I also would suggest fabbing up a mount of some sort to put the tranny on its side. Also, I don't know if it is just me, or the tires, but the track width looks a little wide for that wheelbase. I wonder if when you lock the suspension, if you can lock the a arms futher down in their stroke, to narrow the width and increase clearance.

[JamboreeTJ]

Thanks for the thoughts guys.

I'm def going to cut that brace and streamline it so it flows better. It doesn't hang down much lower then the drive shafts in the current config, so I'll get to removing it a little later. I like the way the links mount to it providing protection for the drive shafts, stabilizing the axles from swinging, and I hope helping prevent some torque twist from the motors. We'll see when I get it running again.

Tipping the tranny sideways wouldn't be too difficult, I guess. But I'll probably wait until the next round of mods when I ditch the twin titan motors and go with a single lathe.

The track width is stock at about the tightest position without causing interference at the A-Arm and axle shaft. The wheel base is just under 17" right now. It might be the pics too. It looks pretty proportional sitting in the basement, but I don't have a lot to compare it to. I've never seen another crawler except on this forum and other pics online.

[toyofast]

You need to pick..... IFS/IRS or Solid axles. You can't run both and have it run good.... it'll run like crap.

Once you decide, setup the transmission so you don't have problems. Lay that shit down on it's side. Cut off a motor mount. Run a single motor, 55 or 65 turn. Mod the EVX if you have too for a single battery. My sons Maxx runs a single 55 turn and the EVX. He gets about 40 minutes of runtime on his 99.9% stock Maxx.



That will get you started in the right direction. No need to build a rig 3-4 times before finding out that it was wrong. Other than that, you are headed down the correct road. I'm not sure if the Pimpcane knock off will ever work on a shafty crawler.

[JamboreeTJ]

Originally Posted by toyofast

You need to pick..... IFS/IRS or Solid axles. You can't run both and have it run good.... it'll run like crap.

Once you decide, setup the transmission so you don't have problems. Lay that shit down on it's side. Cut off a motor mount. Run a single motor, 55 or 65 turn. Mod the EVX if you have too for a single battery. My sons Maxx runs a single 55 turn and the EVX. He gets about 40 minutes of runtime on his 99.9% stock Maxx.



That will get you started in the right direction. No need to build a rig 3-4 times before finding out that it was wrong. Other than that, you are headed down the correct road. I'm not sure if the Pimpcane knock off will ever work on a shafty crawler.

The A-Arms are getting locked today/tomorrow so the 4WIS will be taken care of.

I'll run this around with the motors/tranny as-is for a little bit just to get the feel for it. I'd just have to cut/drill a new c-channel to lay the tranny on it's side and rework the axle braces. No biggee. It is my first crawler so I don't mind experimenting a bit and learning from my own (sometimes bad) experience. I have plenty of angle stock too if the c-channel doesn't work. And if the torsion idea doesn't work well at all, I don't mind building a 4-link. It is really only for screwing around. There's not enough organized R/C activity where I am and I don't know of any comps close enough to think about participating.

Looking around at some more torsion pics, I'm surprised I didn't notice the tranny on the side thing. I guess that is one mark aginast me for moving along to fast.

To be honest, I hadn't looked at the Pimpcane until after I decided to use c-channel. I'd obviously seen the chassis name around here on the forum, but I never looked at the design with any interest. I thought the c would provide better vertical stability than taller angle stock. Then when I saw the Pimpcane while I was doing some detailed searching on torsion chassis, I thought I was maybe on a good track.

[JamboreeTJ]

Links are locked and new moabs/mambos installed.

[spookyseven]

Looks like a good start, have you thought about trimming the skid plates. They seem like they would get in the way and just break off. Im talking about the part in front of the front bulkhead and rear of the back bulkhead.

[JamboreeTJ]

Originally Posted by spookyseven

Looks like a good start, have you thought about trimming the skid plates. They seem like they would get in the way and just break off. Im talking about the part in front of the front bulkhead and rear of the back bulkhead.

Yeah, I think I'll at least bend them upward/inward some more. Depending on how the rear steer gets mounted I'll need to check for interferences.

[Toph]

Actually if you link up your steering and then bend the skidplates so they are very close to the links in the steering it would probably help alot. Then you wouldn't be getting caught on the steering links. But then cut the skid plates so the are just above the steering links. Just a thought.

[JamboreeTJ]

Originally Posted by Toph

Actually if you link up your steering and then bend the skidplates so they are very close to the links in the steering it would probably help alot. Then you wouldn't be getting caught on the steering links. But then cut the skid plates so the are just above the steering links. Just a thought.

Good idea. I got the rear steer servo mounted last night and I think I'll do just that. For the front, I'm using the stock steering gear in the stock location. I'll probably just bend that skid plate upward and give it a trim.

Thanks for the suggestions.

[Toph]

Do you mean keeping the same linkages and mounts that came stock? I have had some very bad experiences with this setup on my stock Maxx. It took alot of the power away from the servo by the time it got to the tires, so it was alaways too weak. I would seggust just putting in one long link going from knuckle to knuckle and then a smaller link from the knuckle to the servo. I have found that for me this is what is easiest to use and very easy to fix if it breaks. If you look at some of the other builds in the Maxx section you will find that many steering setups are this way. I run it this way on my compitition Maxx but in the front it has a behind the axle steering linkage. Just a thought.

[JamboreeTJ]

OK, I just was working on the crossover steering on the back and got the servo mounted. HD and Lowes didn't have any tubing to fit over 6-32 all thread so I just bought some solid rod. I'm going to try and bend that up tomorrow or later in the week.

I have enough to fab up a front system too. It will actually be easier to mount the servo in the front if I go crossover. I think it will have to go in front of the axle for front steering though. I was hoping to keep it BTA. Maybe I can squeeze the drag link in BTA.

After fiddling with getting the front stock linkages set up this evening, I wasn't happy with the toe-in. Since the a-arms are cranked, I've max'ed out the adjustment and the tires are still a touch toe in.

[Toph]

It is still possible to keep it bta but the servo mount itself will just be alot hardder to find a place to put it. The thing that I have found that fits over the links is 1/4" brakeline or 5/16" brakeline. Post up pics of the steering when you get a chance!

[JamboreeTJ]

Almost done!
Still need to mount the body, batts in a better place, and a tranny skid.

[Toph]

The steering looks really good . Looks like you already have some twisting in the axleshafts going on. Put in some CVDs and you won't have to worry about your axleshafts breaking. Except if you suddenly get alot more power then planned. Keep up the great work!

[JamboreeTJ]

Originally Posted by Toph

The steering looks really good . Looks like you already have some twisting in the axleshafts going on. Put in some CVDs and you won't have to worry about your axleshafts breaking. Except if you suddenly get alot more power then planned. Keep up the great work!

You like those shafts, huh? The soil around my house is very sandy. I pushed the maxx up against the wall of my house in one of the flower gardens and proceeded to do a couple 4 wheel dirt burnouts.

I have to get some electronicals sorted out with the 4WS before I think about spending on cvds. The EVX can't handle the 2 servos and ESC now.

Got the body mounted and a tranny skid plate made up today.

[JamboreeTJ]

I reworked this a bit over the weekend because I thought it was looking a bit sloppy.

I've made a new motor mount with the trans still upright, but mounted on top of the chassis rail for a bit better BOA. The mount is a lot cleaner now.

I've also made a hoop for the body that runs perpendicular to the chassis rail as the original design limited flex to a large degree. It made things a lot stiffer.

There seems to be one quirk that I can't quite figure out. Statically, flex is pretty symetric front and rear, and left to right. However, dynamically (like when climbing one tire up a wall) one side is significantly stiffer than the other. Specifically, climbing the left front tire up the wall produces almost no flex/droop in the right side. Conversely, if I climb the right side up the wall it will twist about 70* before lifting the right rear tire.

If I just lift one side or the other by hand there isn't much difference in flex. ????? I'm puzzled.

I'll see if I can post up some pics or a vid tonight or tomorrow.

[HndsWthtShdws]

Your pivot point isnt in the center of the axles, so one side will swing more than the other.

[JamboreeTJ]

Originally Posted by HndsWthtShdws

Your pivot point isnt in the center of the axles, so one side will swing more than the other.

I thought that too, but it isn't off by much and the short side droops more than the long side. I'm not convinced that is it.