jebster's half track lcc mog

[joe122]

Wow, there's a ton of imagination and skill being shown here! That is an awesome build. Very outside the box. Very well done.

[jebster]

Originally Posted by joe122

Wow, there's a ton of imagination and skill being shown here! That is an awesome build. Very outside the box. Very well done.

Thanks for the feedback. I do like just being creative with these builds.

Finally got the winch installed and wired up. Calibrated the ESC to the radio and fired it up. I have to say I'm a little disappointed. I was expecting a lot of pulling power given the reduction the worm drive would provide but it really lacks power. I can get it to stall without much effort. I'm guessing the 380 sized brush less motor I'm using just doesn't have enough muscle. The gearbox, spool and mounts are all working great. I wanted to avoid a 540 sized motor sitting on this but that may have to be a future upgrade.

Still more finishing work to go so I'll have to address this later.

[jebster]

One other thing I noticed that I'm not sure how to handle. When the rig is running and I turn the wheel it causes the whole chassis to tilt the opposite way. It is enough to actual reduce the actual steering angle, like some form of bump steer. Its as if the wheel hub is binding and the servo pushes up/over to compensate. I've checked the hubs and they pivot smooth, no binding.
I've done chassis mounted servos with 4-linked suspsenion on other rigs and didn't see this issue before, or at least not serious enough to notice. This rig does have longer front links than my previous setups but not a lot. Also, my shock setup is pretty soft as I like a spongy feel. Maybe stiff springs?

So, any thoughts? Stiffer springs, a sway bar,.... ??? Keep in mind I have a few limitations. I can't change to an axle mounted servo or go to a 3-link with panhard (although I'm not sure that would help either).

[DORK VADER]

Sounds like you need to be running a panhard bar. Very cool build.

[jebster]

Originally Posted by DORK VADER

Sounds like you need to be running a panhard bar. Very cool build.

You think so? I understand how a panhard helps with bump steer. I'm struggling to visualize how it would help with chassis roll.

And thanks for the compliment!

[DORK VADER]

Try a mock up bar. Keep it in line with the drag link.

[lonleycreeper]

Originally Posted by jebster

You think so? I understand how a panhard helps with bump steer. I'm struggling to visualize how it would help with chassis roll.

And thanks for the compliment!

Definitely. The pan hard bar actually controls axle movement from side to side. What is happening is the axle is trying to go to the side, but your triangulated 4link is stopping it, causing the chassis to move up instead, forcing flex if you will.

Bumpsteer is caused when one of your links are shorter than the other(pan hard/steering) so they need to be the same length and parallel.

[jebster]

Originally Posted by lonleycreeper

Definitely. The pan hard bar actually controls axle movement from side to side. What is happening is the axle is trying to go to the side, but your triangulated 4link is stopping it, causing the chassis to move up instead, forcing flex if you will.

Bumpsteer is caused when one of your links are shorter than the other(pan hard/steering) so they need to be the same length and parallel.

makes sense. weird that my other 4-linked, CMS rigs don't have the issue. or maybe the geometry is different enough I don't see it.

this is going to be a problem between I don't know if I have a clear path to run a panhard. with the tranny dropped low and the servo/drag link right up front it is tight. going to have to thread the needle!

[jebster]

a couple questions about a panhard setup:

1. I will need to remove one of the upper links. shouldn't matter which one, right? since I'm not having an issue with upper link clearance I could go either way.
2. the panhard bar should be the same length as the draglink and a close to parallel as possible. does it matter how aligned (left to right) it is with the draglink? I will probably have to have it offset by 1-1.5" giving the available space and mounting points.

I'm going to try the 3-link/panhard on the front to see if that helps the body roll. given I have the same 4-link/CMS setup on the rear axle I may have to change that over also but I hope that is not necessary.

[DORK VADER]

Originally Posted by jebster

a couple questions about a panhard setup:

1. I will need to remove one of the upper links. shouldn't matter which one, right? since I'm not having an issue with upper link clearance I could go either way.
2. the panhard bar should be the same length as the draglink and a close to parallel as possible. does it matter how aligned (left to right) it is with the draglink? I will probably have to have it offset by 1-1.5" giving the available space and mounting points.

I'm going to try the 3-link/panhard on the front to see if that helps the body roll. given I have the same 4-link/CMS setup on the rear axle I may have to change that over also but I hope that is not necessary.

1. The upper link and panhard pivot points/mounts have to be located on the same side of the axle.

2. If there is no binding in the rod ends or the links when cycling the suspension and the panhard bar is the right length for whatever crazy angle, it should work. Technically though everything needs to be inline/parallel as possible.

[SMW]

Sorry coming in a little late to this party, but had a few questions. What brand of tracks are you running and do they come in different sizes like the 1.9 and 2.2 wheels/tires? Also do tracks require a higher rated torque servo than for tires?What are your servo specs ? I have never dealt with tracks but now am thinking they might be fun to run in the snow. Also are you set up to turn both back and front separately or do they always turn in unison? I was thinking about almost moving in a sideways direction, to get out of some awkward positions ( both front and back turned in same direction ) moving diagonally not in a circle. Sorry I just have too many questions and am not helping your build any .

[jebster]

Originally Posted by SMW

Sorry coming in a little late to this party, but had a few questions. What brand of tracks are you running and do they come in different sizes like the 1.9 and 2.2 wheels/tires? Also do tracks require a higher rated torque servo than for tires?What are your servo specs ? I have never dealt with tracks but now am thinking they might be fun to run in the snow. Also are you set up to turn both back and front separately or do they always turn in unison? I was thinking about almost moving in a sideways direction, to get out of some awkward positions ( both front and back turned in same direction ) moving diagonally not in a circle. Sorry I just have too many questions and am not helping your build any .

I'll try to answer some of our questions.

The tracks are from rc4wd and there is only one size. As for a servo that's your call. The tracks are heavier than wheels so I try to use high torque servos, but I would do that normally. I don't remember what the specs on these servos are but it is probably over 200oz of torque.

For steering I have mine set up so that I can select the steering configuration. I can do front only, rear only, normal (both axles pointing the same direction) and reverse (axles pointing opposite directions).

[clarketian]

Great work! Are you planning to make portal reduction for this rig?

[jebster]

Originally Posted by clarketian

Great work! Are you planning to make portal reduction for this rig?

Thanks. And no portals on this rig. The LCC axles have plenty if reduction already.

[jebster]

Converter the front to 3-link/panhard and I'm impressed with how much it improved the body roll. The front holds solid. Now it makes the lean from the rear axle more apparent. So that means I need to convert the rear over next.

[Tantaran69]

This looks sick, great looking rig Sir....

[DORK VADER]

Nice work.. Problem solved.

[jebster]

Spend the evening converting the rear to the 3-link/panhard setup. Took a little while because I had to slide the servo back to get more clearance. But it all worked out nicely. It is amazing how much these changes made. No body roll and it tracks straight when not turning.

Here are couple pics and a short video showing how tight this thing can turn.

https://youtu.be/BQ0mKrj8W3g

[jebster]

Got to work on the last major part I plan to fab up, the front bumper. Got the center structure done bit was looking for opinions on what to do on the sides. I have pics of two options (2 pics each). Let me know what people think might look best. I'm leaning one way.

[Sammy J.]

I think they both look fine, but I'm leaning toward the double bend version. It's just a little more stylish.


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