Land Cruiser 80 Crawler (WIP)

[VKTechnic]

I saw this photo on an R/C forum post...and now I'm hooked on crawlers:

I've set about building my own crawler based on the above picture, and I'll post WIP photos here. Your feedback is greatly appreciated.

To start the WIP photos, here's the chassis as of today:

[Lakop]

Hi,

Why not build something similar to 8081 and turn it into a crawler? For your chassis I would try a shorter wheel base.

Keep us updated with your progress.

H

PS: I just looked at your photostream. Excellent work.

Edited August 30, 2013 by Horace T

[VKTechnic]

Hi,

Why not build something similar to 8081 and turn it into a crawler? For your chassis I would try a shorter wheel base.

Keep us updated with your progress.

H

PS: I just looked at your photostream. Excellent work.

I'm keeping the wheelbase a little longer because I plan on buying some third party tires hopefully within the next month, and they're going to be noticeably larger.

[MrNumbskull13]

Looks not bad so far! The main thing about crawlers is to keep the centre of gravity as low as possible, and efficient drivetrain helps too.

:)

[VKTechnic]

At ride height with steering motor installed. Next step is adding worm gears to the axles and working on the transmission.

[Junpei]

What are the worm gears for? Nice work so far.

[VKTechnic]

What are the worm gears for? Nice work so far.

Worm gears will be for the drive, I want to move as much gearing into the axles as possible.

[VKTechnic]

Added worm gears to the axles and moved the driveshafts up 2 studs.

[AndyCW]

Worm gear are good for getting a large reduction into a small space, but are terribly inefficient and the knob gears aren't too good either. What gear ratio you use depends greatly on what motors will be used. You don't want to gear it down too much and loose wheel speed. Gear it to get the torque you need and satisfy yourself with the resulting speed. v/r Andy p.s. You are going to want to setup the top spring mounts to provide two degrees of freedom instead of the one that is present in these wip pics.

Edited August 31, 2013 by AndyCW

[VKTechnic]

Worm gear are good for getting a large reduction into a small space, but are terribly inefficient and the knob gears aren't too good either. What gear ratio you use depends greatly on what motors will be used. You don't want to gear it down too much and loose wheel speed. Gear it to get the torque you need and satisfy yourself with the resulting speed. v/r Andy

In crawlers I usually like to have low wheel speed -- I'm going for one L-motor and a 24:1 gear reduction.

For tires I'm thinking these or these tires.

[AndyCW]

24:1 WOW I am not sure that you will be happy with this setup. Excessive torque and exceptionally slow.

[VKTechnic]

24:1 WOW I am not sure that you will be happy with this setup. Excessive torque and exceptionally slow.

I'm not going for speed here. Remember: this is a crawler. I want a controlled climber, not a dragster

[Lipko]

Reduction is okay, but aren't those 8-teeth gears too weak? The smaller the gear the bigger force it has to bear to transmit the same torque. You placed the smallest gear on the highest torque axle.

On the front axle the gear isn't even supported properly, the axle with the gear will just bend out and won't transmit the torque.

Edited August 31, 2013 by Lipko

[GuiliuG]

You same don't use portal axle ?! I can see that your joint will break as soon as you will climb to important obstacles !

[MrNumbskull13]

Portal axles are the best way to get gear reduction, also I don't think you'll need a 1:24 reduction. Watch 'zblj1987's trial truck tip 1'. I suggest that you use a gearing that suits the weight of your crawler. :)

[Junpei]

I agree, I think you should get rid of the worm gears, there is too much efficiency lost to friction. If you put it through a crawler course right now, you'll have some seriously ground up liftarms. I suggest just using portal axles and maybe limited slip diffs. There is always room for gear reduction in the middle, too.

[VKTechnic]

Wow, didn't think I'd get so many complaints for using worm gears. I'll go ahead and get rid of them.

About portal axles: I don't want to use them because they move the steering pivot point further away from the wheel. I want to limit wheel movement due to steering as much as possible, and I don't want to set up a complex steering setup with kingpin inclination etc. As they are right now, the axles provide decent ground clearance, so moving the driveshaft down won't change much.

[GuiliuG]

The question is rather : do you want to break some joints or to move the steering point further away from the wheel ?

[z3_2drive]

I think I managed to damage even the new 8t gear with a worm gear and an L motor, so it's just a heads-up that you might risk damaging something and not to mention the crawler will be dreadfully slow, which some people do but it just gets boring to watch when they move at a snail's pace. Crawlers are easy to control even when they have a decent speed. If you still want to go with your idea the best thing to do is to test your worm gear idea and either prove us wrong or realize your mistake so you will remember it for the future. And having a 'Version 1' is always good so you can find any additional things to improve on, such as your suspension which I am eager to see how it handles

Edited August 31, 2013 by z3_2drive

[AndyCW]

The newer wheel hubs might be a solution to your strength issue. They also move the steering pivot further inside the wheel and will reduce the forces on the steering rack. The question is whether or not they are stronger than the u-joint style hub. Testing is how we all learn about the limits of these parts. I am eagerly awaiting the results of this. It also looks like you are using the old 8t gears on the axle. Scaling up crawlers creates many issues. Good luck. v/r Andy

[VKTechnic]

The newer wheel hubs might be a solution to your strength issue. They also move the steering pivot further inside the wheel and will reduce the forces on the steering rack. The question is whether or not they are stronger than the u-joint style hub. Testing is how we all learn about the limits of these parts. I am eagerly awaiting the results of this. It also looks like you are using the old 8t gears on the axle. Scaling up crawlers creates many issues. Good luck. v/r Andy

Only problem with new wheel hubs: I don't have any

[VKTechnic]

Thanks everyone for the feedback, both positive and negative, rude and polite.

I've changed the axles once again, this time they have 1.667:1 reduction instead of a worm gear system. Also added some gearing in the chassis and a 2-speed gearbox. Final gear ratios are 8.333:1 (first gear) and 2.778:1 (second gear).

Oh, and yes I did cut an old style differential to get that clutch gear.

EDIT: I also made a short video of the new axles, it can be found here.

Edited September 1, 2013 by Victor Kojenov (TFOL)

[Junpei]

Looks great! Are you sure 1 L-motor is enough?

[AndyCW]

This looks promising. I hope you enjoy the build. I worry about the 12t bevel to 20t double bevel in the center section. I have seen the pinion gear climb the ring gear and cause gear deflection and then the 12t bevel gear ground its teeth off. However; with only one PF Large for power there should not be any problems. After seeing some of your other work, I am eager to see the results of this project. v/r Andy

[VKTechnic]

Looks great! Are you sure 1 L-motor is enough?

Should be enough, tested it and it can go up a flat wall. Haven't done an outdoor test yet though.