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Old 01-15-2018, 07:36 PM   #1
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Default Jebster's 10x10 HEMTT rollback hauler

Decided on my next project. I have a 6x6 so I decided the next addition should be big. And I've always liked the look of a HEMTT so I'm combining the projects. It won't be true to scale but something different.

Drivetrain is going to have each axle separately driven off a single shaft that runs down the spine of the truck. Each taps in via a separate transfer case with another transfer case reversed to connect in the transmission. Yes, that is 6 transfer cases. Thank goodness for cheap ebay products from China!

I already did a little mockup of the body using my favorite material, cardboard. I don't think it came out too bad for 30 minutes worth of effort. I want to find a body or have one 3d printed (saw files on thingiverse), which I feel is going to be the most cost effective solution.

The bed is going to have a screw drive to rollback the bed. Not sure about the tilt mechanism yet.

This build is going to take a while as I still need to get some parts and I have a couple other projects I'm working at the same time.

Here are a few started pics.
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Old 01-15-2018, 08:29 PM   #2
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Default Re: Jebster's 10x10 HEMTT rollback hauler

Quote:
Originally Posted by jebster View Post
Decided on my next project. I have a 6x6 so I decided the next addition should be big. And I've always liked the look of a HEMTT so I'm combining the projects. It won't be true to scale but something different.

Drivetrain is going to have each axle separately driven off a single shaft that runs down the spine of the truck. Each taps in via a separate transfer case with another transfer case reversed to connect in the transmission. Yes, that is 6 transfer cases. Thank goodness for cheap ebay products from China!

I already did a little mockup of the body using my favorite material, cardboard. I don't think it came out too bad for 30 minutes worth of effort. I want to find a body or have one 3d printed (saw files on thingiverse), which I feel is going to be the most cost effective solution.

The bed is going to have a screw drive to rollback the bed. Not sure about the tilt mechanism yet.

This build is going to take a while as I still need to get some parts and I have a couple other projects I'm working at the same time.

Here are a few started pics.
Cool project, jebster.
I think what you're after is an M1074/1075 Palletized Load System, PLS. They're more or less a rollback that can detach it's flat bed or load.
Also the front 2 axles and the 5th axle are steer axles. In real life they don't turn for sh!t, but it might help in scale since SCX 10 axles have way more steering through.
Good luck with your build.

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Old 01-16-2018, 05:11 AM   #3
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Default Re: Jebster's 10x10 HEMTT rollback hauler

I've considered building the PLS for mine as it could be used to load/unload a flatbed for hauling a truck. the challenge is i feel i would need some type of hydraulics to get enough lifting power and i'm not prepared to go that far.
i ididn't realize the 5th axle also steering (I've only been around the 8x8 versions). something to consider. i don't have high expectations for turning radius on this one but every little bit will help.

looking forward to getting some build time on this one.

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Cool project, jebster.
I think what you're after is an M1074/1075 Palletized Load System, PLS. They're more or less a rollback that can detach it's flat bed or load.
Also the front 2 axles and the 5th axle are steer axles. In real life they don't turn for sh!t, but it might help in scale since SCX 10 axles have way more steering through.
Good luck with your build.

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Old 01-16-2018, 05:14 AM   #4
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Default Re: Jebster's 10x10 HEMTT rollback hauler

i did have a question for the other rcc members. given the transfer cases in my setup will cancel out and provide a 1:1 from the input to the axles i wasn't sure what transmission would be appropriate. i could always drop in an scx10 style transmission but in the interest of space i was considering a GRU. if i went that route what ratio would be the best? i was thinking 5:1 with a high turn motor might work but i want to make sure this thing has plenty of low speed torque.
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Old 01-16-2018, 07:51 AM   #5
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Default Re: Jebster's 10x10 HEMTT rollback hauler

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Originally Posted by jebster View Post
i did have a question for the other rcc members. given the transfer cases in my setup will cancel out and provide a 1:1 from the input to the axles i wasn't sure what transmission would be appropriate. i could always drop in an scx10 style transmission but in the interest of space i was considering a GRU. if i went that route what ratio would be the best? i was thinking 5:1 with a high turn motor might work but i want to make sure this thing has plenty of low speed torque.
I would consider making your axles pass through, since it's relatively easy to do with SCX 10 axles. That would give back some gear reduction and simplify your drive train.
If not, you would need a decent amount of reduction through a GRU. Maybe you could add a gear reduction transfer case into the drive line?

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Old 01-16-2018, 08:02 AM   #6
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Default Re: Jebster's 10x10 HEMTT rollback hauler

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Originally Posted by jebster View Post
I've considered building the PLS for mine as it could be used to load/unload a flatbed for hauling a truck. the challenge is i feel i would need some type of hydraulics to get enough lifting power and i'm not prepared to go that far.
i ididn't realize the 5th axle also steering (I've only been around the 8x8 versions). something to consider. i don't have high expectations for turning radius on this one but every little bit will help.

looking forward to getting some build time on this one.
That would be complicated and expensive to pull off in scale with hydraulics. Might be able to use electric actuators, which aren't as expensive. It would be cool to see someone build a functional PLS or something similar.
I know there is a build on here where a guy used a New Bright CXT cab for a roll back, and used actuators to make the bed work.

Real PLS's have a lot of positive camber on the rear axle to make up for the limited amount of throw it can turn. Pretty complicated and failure prone in real life.

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Old 01-16-2018, 09:10 AM   #7
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Default Re: Jebster's 10x10 HEMTT rollback hauler

This is going to be epic!
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Old 01-16-2018, 09:39 AM   #8
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Default Re: Jebster's 10x10 HEMTT rollback hauler

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Originally Posted by tcanin00 View Post
That would be complicated and expensive to pull off in scale with hydraulics. Might be able to use electric actuators, which aren't as expensive. It would be cool to see someone build a functional PLS or something similar.
I know there is a build on here where a guy used a New Bright CXT cab for a roll back, and used actuators to make the bed work.

Real PLS's have a lot of positive camber on the rear axle to make up for the limited amount of throw it can turn. Pretty complicated and failure prone in real life.

Sent from my HTC Desire 626 using Tapatalk

the CXT cab build is one I had looked at and will probably model some of the rollback bed features from that in mine. I've been working with electric actuators in some Tonka truck rc conversions i'm doing. they work but the power does leave something to be desired.

Quote:
Originally Posted by tcanin00 View Post
I would consider making your axles pass through, since it's relatively easy to do with SCX 10 axles. That would give back some gear reduction and simplify your drive train.
If not, you would need a decent amount of reduction through a GRU. Maybe you could add a gear reduction transfer case into the drive line?

Sent from my HTC Desire 626 using Tapatalk
I've done pass throughs on my other 6x6 build so I wanted to do something different on this one. with all the transfer cases locked together it becomes a solid driveline so each axle gets power at the same time without any lag due to slop through a pass through.
you are correct that i'll probably have to go with an scx10 style transmission vs gru to get the necessary reduction.
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Old 01-16-2018, 09:39 AM   #9
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Default Re: Jebster's 10x10 HEMTT rollback hauler

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This is going to be epic!
not sure it will be epic but i'm going to have fun trying! thanks
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Old 01-16-2018, 10:48 AM   #10
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Default Re: Jebster's 10x10 HEMTT rollback hauler

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Originally Posted by jebster View Post
the CXT cab build is one I had looked at and will probably model some of the rollback bed features from that in mine. I've been working with electric actuators in some Tonka truck rc conversions i'm doing. they work but the power does leave something to be desired.



I've done pass throughs on my other 6x6 build so I wanted to do something different on this one. with all the transfer cases locked together it becomes a solid driveline so each axle gets power at the same time without any lag due to slop through a pass through.
you are correct that i'll probably have to go with an scx10 style transmission vs gru to get the necessary reduction.
I'm glad you're familiar with that build and the use of actuators.


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Old 01-16-2018, 11:53 AM   #11
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Default Re: Jebster's 10x10 HEMTT rollback hauler

to tilt the bed I would like to find a way to have it done without any powered components (actuators, servos, etc.). my idea is to have some type of dry piston that props the bed up as the screw drive slides the bed back. once the bed get about halfway back the piston is at full compression and forces the bed to start tilting up. kinda like a tent post pushing up the tent. with the right angle it could work and it means one less part to fail. this might put some stress on the screw drive but I can always beef up the motor driving that.
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Old 01-17-2018, 08:30 AM   #12
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to tilt the bed I would like to find a way to have it done without any powered components (actuators, servos, etc.). my idea is to have some type of dry piston that props the bed up as the screw drive slides the bed back. once the bed get about halfway back the piston is at full compression and forces the bed to start tilting up. kinda like a tent post pushing up the tent. with the right angle it could work and it means one less part to fail. this might put some stress on the screw drive but I can always beef up the motor driving that.
This sounds like a solution.
Real PLS's set the bed completely on the ground by moving two sets of hydraulic cylinders in an arc. The first set raises the hook at the front of the bed to about 45* while sliding it back on rollers on the top of the truck's frame. The second set moves the hook further in the arc and sets the bed on the ground.
Pretty neat to watch. I'm sure you can find videos on YouTube. I'm trying to conserve data otherwise I'd look one up and post it.
This operation might be easier to pull off than making it work like a roll back.

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Old 01-18-2018, 07:14 AM   #13
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Default Re: Jebster's 10x10 HEMTT rollback hauler

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Originally Posted by tcanin00 View Post
This sounds like a solution.
Real PLS's set the bed completely on the ground by moving two sets of hydraulic cylinders in an arc. The first set raises the hook at the front of the bed to about 45* while sliding it back on rollers on the top of the truck's frame. The second set moves the hook further in the arc and sets the bed on the ground.
Pretty neat to watch. I'm sure you can find videos on YouTube. I'm trying to conserve data otherwise I'd look one up and post it.
This operation might be easier to pull off than making it work like a roll back.

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I've found videos on this setup. I've even seen someone do it with an rc truck. it would be cool but I think it would require hydraulics to make it work, which i'm probably not going to try on this build.
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Old 01-20-2018, 08:07 AM   #14
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Default Re: Jebster's 10x10 HEMTT rollback hauler

Had a little time yesterday to work on this rig. I'm using some aluminum c-channel for the rails. I drilled out mounting holes for the transfer cases (I did a number of extras in cases I want to make axle-to-axle spacing adjustments) and mounted them up. Dropped an ax2 tranny up front just to see how it sized up. I'm most likely just going to go with a standard scx10 tranny because I don't think I will need a 2-speed.

The one challenge this set is going to have is driveshaft angles. I will need short driveshafts (~65mm) and have the axles clocked a lot to prevent binding. That is ok for the rear axles but for the front I'm going to have to be creative. I'm thinking beeftubes so I can drill new c-hub mounting holes through the axle housing.

Next thing to work is the suspension links and chassis mounting brackets.
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Old 02-02-2018, 10:06 AM   #15
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Default Re: Jebster's 10x10 HEMTT rollback hauler

Still waiting on a bunch of parts but I was able to pay out my link geometry. This setup provides a lot of travel for each wheel. Even the tamiya semi driveshafts I bought for nicely.
I do believe I want to go with a cantilever setup for the shocks so they are low and don't interfer with the operation of the bed. Only problem with that is I'm not sure what rocker arm to get. I need about 1.5" of upward travel. If someone knows whether twin hammers rockers or traxxas 1/16 summit rockers give that much travel let me know. I ask about those because I can get a bunch cheap (and with needing 5 sets the cheaper the better!).
Next step is to replace my lexan link mount plates with aluminum and then mock up the front steering axles. Those will be more challenging in that I need to have enough room to run panhard bars and steering links around the pumpkins and transfer cases. Should be fun!
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Old 02-06-2018, 06:49 PM   #16
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Getting a slow trickle of parts coming in but not enough to make big progress.

I am looking for opinions on tires and wheels. Given I will need 12 total (10 + 2 spares) and I don't want to break the bank what are the best options out there? I'm OK with no-name brands and ebay products from China. I would like 1.9 beadlocks (plastic or metal) and tires in the 120mm (~4.5") ramge. I saw some trx4 tactical sets out there for cheap I was considering. They are glued on but I could live with that for a decent look and compound.
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Old 02-16-2018, 04:26 PM   #17
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Default Re: Jebster's 10x10 HEMTT rollback hauler

Made some more progress. Got the rear axles mounted with links. Have the front mostly done, just need to make a chassis mount for the panhard bar, which is going to have to weave a path around the pumpkin and chassis rails.
Ordered up 3 sets of cheap tires and beadlocks wheels on eBay ($100 for 12 tires nd aluminum beadlocks is not bad, even if the quality is a little low).

Next will be getting shocks figured out. If I can get some hard springs I might be able to have some installed laid down a little and avoid the cantilever setup. Time will tell.
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Old 02-24-2018, 12:06 PM   #18
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Check eBay for cheap tires and wheels. Chinese knock offs can be had for under 25 for 4 and offer very good traction

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Old 02-25-2018, 03:21 PM   #19
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Check eBay for cheap tires and wheels. Chinese knock offs can be had for under 25 for 4 and offer very good traction

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Got some tires and wheels coming in from China. We'll see how they work.

I got some time to work on the suspension and steering. The cantilever are twin hammers parts. Ran out of rod ends before I could finish the front axles though. Everything moves smoothly, just need to find some inexpensive shocks. The steering uses some tamiya semi steering blocks connected together and then to the servo.
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Old 03-11-2018, 06:27 PM   #20
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Default Re: Jebster's 10x10 HEMTT rollback hauler

So the tires & wheels from China arrived and I'm pretty happy. Tire compound is good and the wheels seem pretty sturdy. Foams are soft but I'll run them for awhile.

Also started getting parts in for the rollback feature. My plan is to have the motor connected to the threaded shaft via a belt and pulley system. When the motor spins it will push or pull on the shaft which will be fixed to each end of the bed. Still have a lot of mock up to do but the ideas are flowing.
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