another ax10 build, it's a 2.2 esse

[opek]

At the last comp I broke the rear upper link mount. The tube on top of the axle housing sheered off of the axle housing. That's what I get for using only 2 screws. If it doesn't kill you, err if all of the parts didn't break it can only go back together better.

Originally Posted by Nabil

Your rear upper plate is horrible, use this.

Good idea! Increasing the vertical spacing between the rear uppers and lowers made a huge difference in torque twist, without affecting the antisquat too much. edit: I don't believe this is true.

Nabil threw me a pair of TLT link brackets I just screwed into my upper plate. I gave the uppers like 1/16" more triangulation. Thanks!

As soon as I got the truck working good, I went and broke it again. I made these little cutting board pieces, about 1/4 x 1/2 x 3/4, to raise the rear lowers up. I screwed them into the 2 little holes on top of the axle housing. While it looks great and has all sorts of awesome ground clearance, it crushed the influence the chassis had over the axle, and all that torque twist is back. EDIT: I think this is all from a smaller antisquat value. In addition to figuring that out I will have to do a bit of brainstorming about how I want the shocks setup.

I got the black rear springs, but I have ruined the damn thing before even trying them. They are just a bit softer than my under-a-book golds, low shock angles or more books are probably in store. The way they are laid down right now, witht the binding in the links sorted just right, it's like they have an effective linear rate! Or maybe I'll just figure it out!

Went back to a 1.25" wheel on the front. Rovers on 1.25" wheel, siped and whatnot. Proline dual stage foam, untrimmed. With a 1/4" Losi pink disc on the outside sidewall. I still think an internal plastic disc would do more for the sidehill, but there is only one way to find out.

The rears are still full width claws on .7" wheels with 75% of the width of a a proline dual stage foam.

The whole truck is a bit narrower than I would like (~10.5" up front), but without doing some ****ed up shit to my steering I don't think I can widen it. Don't buy SDS axles for your axial, lol.

Pics to come when I get my camera fixed and hopefully figure some of this out.

[opek]

It only took 7 months, but there is a chance I just "got" something about the rear end of a 4 link. I think I understand how those sweet mounts I made for my rear lowers, which made them exactly parallel to the ground, ruined my geometry.

Quick background on the seemingly super basics that I failed to grasp:

Instant Center: When viewed from the side, the point of intersection of the rear upper and lower links if they were extended to infinity.

Normal Line: When viewed from the side, the line drawn from the center of the front axle at the height of the center of gravity of the chassis to the center of the contact patch of the rear tire.

When the instant center traces the normal line, you have 100% anti squat, below more and above less.

When viewed from the side, if the instant center is located in front of the COG the vehicle will tend to raise the front end. If it's located behind the COG the vehicle will tend to raise the rear.

I have been so obsessed with my narrow understanding of squat and antisquat I entirely neglected the bits and pieces I read regarding the instant center relative to the behavior of the vehicle.

I have lots of anti squat, sometimes enough to cause excessive wheel hop, but all while still looping out backwards. At one point my rig worked exceptionally well. It would slam the front end down even when climbing near vertical surfaces. I am going to guess this is because while my antisquat has remained relatively constant, the location of my IC relative the COG was changing drastically.

My next goal is going to be to slam the IC way back behind the COG while keeping an appropriate amount of anti squat to suit my suspension, foams, tires, course, and level of driving aggression .

I hope I didn't get drunk and embark on a huge and worthless journey.

Next step is find the god damn proofs for why the normal line exists, and why any of these rules exist.

Thanks for reading!

edit: I think the IC location has minimal effect compared to the antisquat value.

[opek]

Well the rig was working pretty well, which meant it was time to break it all and try and learn something new: so IC test 1 begins. Hopefully I can learn something about IC throughout this. As I progress, I'll be sure to quantify my results to the best of my abilities. From the old to the new.

[opek]

I drove it around till it broke (it's just thin plexiglass for easy cutting) and it worked surprisingly well. Moving the rear IC back behind the COG and giving it a good bit of anti squat got rid of the torque twist almost entirely. It was able to hang on a ledge by just the front tires and spin the front without hopping or trying to leap off and flip over backwards. Super stable on a sidehill with minimal influence of throttle towards the stability of the truck. The front will dive a centimeter or so and the rear will remain about constant.

I will have to try this in metal or delrin and put it through some bashing.

I added two metal braces about 6 inches long that run diagonally from each shock tower to the one kitty corner. Those raised the COG of the truck up significantly and made the rear antisquat much more reasonable. It broke before I got to play with reverse, which is one area this setup should not excel in.

Anyway, on to more fun in the future! As always, guidance and input is not just valued but can be repaid in beer and song!

[helhedded]

Originally Posted by opek

The whole truck is a bit narrower than I would like (~10.5" up front), but without doing some ****ed up shit to my steering I don't think I can widen it. Don't buy SDS axles for your axial, lol.

Why do you say that?

By the way, I love the look of your old Cab. It flows very well.

[opek]

Originally Posted by helhedded

Why do you say that?

By the way, I love the look of your old Cab. It flows very well.

Cause so many people have those big wide 11" trucks and they make me jealous. Plus the scrub is crazy on the stock setup, although caster and practice have made me less susceptible to sucking because of it.

[opek]

Speaking of sidehills, guess what's next?

[opek]

I can't even hold out for an hour! The alpha stage hybrid tweel is done! It's made of 5/8" vinyl tubing from Home Depot (made in the USA!) that I glued together with some fast drying Discount Hobby Warehouse glue. I might try another with some 3/4" tubing, or even try adding some 1/4" or 3/8" as a second layer.

It's pretty heavy compared to foams, but I certainly won't complain about having it up front.

I will probably end up angling the sides so the bead seats easier. I cut this tweel 1.75" wide, about the width of the rover tread. I might bring the inner width down to 1.5" or less depending on how difficult and awkward the tires are when mounted.

[Trubble]

Interesting. Look forward to seeing how this one pans out.

[Nabil]

Scrub isn't a bad thing, especially on a sportsman. You can use it to lock your front end on ledges

This is probably one if my favorite builds on rcc. You are willing to learn and research why certain things work. That's something I can not say about most people today in our gimme gimme society.

[Trubble]

Originally Posted by Nabil

This is probably one if my favorite builds on rcc. You are willing to learn and research why certain things work. That's something I can not say about most people today in our gimme gimme society.

Precisely why I nominated this thread for Wicked Wolf's giveaway this month.


(click the link, go check it out!) (Better yet, post up a pic and cast a vote!)



Oh, and sorry Opek, if you're offended by me blatantly stealin' your pic without askin' first. No disrespect was intended.

[opek]

Thanks for the kind words!

The foam setup on the tweel shown rolls over a whole bunch, a stiffer foam or a ring is in order. I need to figure out how to get foams in the right thickness or get really good at fileting that stuff. The material used in the losi pinks is very easy to cut, so maybe I will do a bit of reading in that direction.

I finally got a body. It's not the best, but it was at the LHS and I wanted it! Here it is!

[opek]

Here are a few shots of the tweel's mounted. The passenger tire is the version you have seen in the picture. It seems like it has tons of traction, but it's just a bit too soft for predictably (precisely?) driving up and against terrain. The drivers side tweel is exactly the same, except it has the addition of a second layer of latex tubing. Both tweels are 1.8" at the widest and just under 1" where they meet the 1" wheels.

You can also see how I've attempted to lower the servo/battery and **** up my front geometry all at the same time.

[opek]

The whole point of these things is to control how much the tire rolls over on a sidehill. The tubes will flex a little bit up and down but are rigid side to side. I tried using two heights of tweel. One is as pictured: tubes around the wheel with a foam over that. The other one has an additional layer of softer latex tubes on top, leaving a little more than a 1/4 of space for the foam. The shorter tweel worked better. I would like to try one made out of larger tubes, which would be a little taller but softer overall.

They both offered great amounts of traction. The stiffer one with the latex had a bit more traction when tons of weight was put on it, but not nearly as much for grabbing when there isn't much pressure as the one without the latex.

Unless the rig was in a bind, the rollover onto the sidewall was about perfect. But I was out this evening and the memory foam had gotten a bit harder. I've always like the proline foams better when it was around 50* outside, and now more than ever do I really appreciate that extra stiffness. I will need to find something similar.

Here is another shot of the inside and what it looks mounted up.

[Duuuuuuuude]

Learning how to properly tune a suspension setup can be a mind frying thing. Its good to see more people taking the time to tackle it. I need a refresher course myself...

Love the tweel idea.

Originally Posted by Nabil

This is probably one if my favorite builds on rcc. You are willing to learn and research why certain things work. That's something I can not say about most people today in our gimme gimme society.

Amen to that.

[opek]

Originally Posted by Duuuuuuuude

Love the tweel idea.

Thanks, they are working wonderfully so far. My claws caught the clap and they are working so freaking well with the tweels and the soft proline memory outers during the day. The rears I need to sort out, I still haven't picked up a stiffer foam to work with. The front works great during the day and the rear works great at night!

I set up my links a bit differently now and the truck is amazing. It sidehills like a true champion. It's a pleasure to drive off camber and really it's very confidence inspiring. I credit this to my roll axes and neutral antisquat value in the rear.

The front end dives a bit more than I'd like it to and I think I'm losing a tiny bit of traction because of it. I can't make it up some of the hilarious shit I used to. If I can't fix it, oh well, it's a great trade off for the huge benefit to sidehill stability. For the same reason reverse is still a bummer, and I bet raising my front links up on the axle side to set up a more neutral antisquat value will help a lot with both. If I adjust the links for more antisquat as it sits I just end up with too much variation throughout articulation.

I'm pretty psyched, I don't think I've ever had it wheeling this good. Especially since I know there is lots of room on the table with tweels and stiff foams for the rear.

Here are some pics! And a shot of my diy gunnar style mounts (I tapped the delrin cross brace and stuck a 4mm rod through. I lopped off a piece of link material then tapped a rounded it to make a cap. Probably not the lightest but definitely strong!


I wish I could put this text all the way at the bottom... In the picture you can see my normal line in pink, my IC is just out of frame at the meeting of the blue lines, the red lines show where the center of gravity of the chassis meets the axle centerline, and the green lines show my roll axes.

[opek]

In the picture directly above (last picture in the previous post) you can see my normal line in pink, my IC is just out of frame at the meeting of the blue lines, the red lines show where the center of gravity of the chassis meets the axle centerline, and the green lines show my roll axes.

As much as I can think about roll axes, I imagine the proof has to do with the length and location of the links. It seems like it defines the line around which all 4 links rotate. As best as I can understand it, if the majority of the weight of the chassis is above that point, when weight is transferred (due to incline or turning at speed, or binding during turning) there will be more weight transferred above the point so the chassis will pitch to the outside. If more weight is below that point, when weight is transferred the chassis will pitch inward. The place with the most lateral force will pitch. I don't see how this has anything to do with the unsprung weight.

I will have to keep reading and do some sort of silly test.

Super ultra edit - I do all of my geometry considering at halfway through articulation. That coincidentally is about where my truck naturally settles after flexing a bunch. I wonder why.

[opek]

Here are a few shots of the tweels working wonderfully. I still need to sort out a few things, the tire rolling over is one of them. (still ) Sorry I forgot to hit the flower button on the first two shots. The third shot is a lighter load and the last shot is when the tire is fully loaded up. This is a pretty steep, smooth, consistent sidehill and near the max of what the rig can wheel on.

[tomer]

the tire roll is not that bad. if you get good bite for climbs it looks good.

[opek]

I'm getting a little bugged out about weight transfer while turning and climbing. This new higher roll center, while absolutely awesome, is making the rig a bit less likely to drive straight through stuff. It's made my hoppy rear claws almost worthless.

When I'm turning (even as simple as I'm going to turn the wheels for a second of forward motion before I turn them back again) the inside tire is always very strongly sprung and really pushes back on the rig. If I'm going over an obstacle and I turn into it the rear tire will really upset the rig as it passes over. I am using losi blacks in the back, but they are stood up pretty well. Nabil pointed out to me the huge difference in springrate I enjoy when I lay the shocks down, so I'm a bit unsure of where to go. Maybe if I mount the shocks behind the axle or something silly I can soften them up a bit.

I'm also thinking maybe I should try and get the front roll center as low I can without sacrificing stability, to open up the sharp turning possibilities by really putting some weight on the outside front tire.. But at the same time, I want it right up at the CG for awesome and predictable wheeling.

Oh well, it's marginal differences I'm talking about now. Raising the roll center made my rig go from absolutely unstable to amazingly stable.