MadInventor

6x6 1/10 Off Road Truck build

Recommended Posts

After posting in this thread (http://www.tamiyaclu...showtopic=65976) about wanting to see a 6x6 off road truck from tamiya, I decided it wasn't very likely to happen, so went ahead and started buidling one myself.

I started off by building the rear axle walking beams:

img33435_14042013183422_1.jpg

For the gears I used hot bodies 25T 1 module pinion gears.

img33435_14042013183422_2.jpg

img33435_14042013183422_3.jpg

The axle itself is a modified Hi-Lift item. The standard bevel gears with splines in the dif were replaced with TT-01 items which use flats inside the bevel gears instead. i was then able to make my own drive shafts for driving the walking beams, which were loctited into the diff gears.

After that I moved onto making the chassis rails. For this I used some steel box section, which I slit down the middle to make 2 chassis rails. I then tried to fit the rear axle using High llift leaf springs, but these proved to give toomuch height to the chassis, so i used some modified king hauler springs instead.

Once the rear axle has been fitted, I then mounted the front axle. On the original truck I was trying to 'copy', the front axle uses similar suspension to that found on a tractor, but with some shock absorption being provided by a single leaf spring. The single leaf spring proved too awkward to implement, so i went with a simple pivoting system instead.

img33435_14042013183422_4.jpg

The pivot that the axle swings on is a steel pin, which itself has a steel sleeve to rotate within, so there should be no wear issues there. Again, I used a hi lift axle for the front axle, but with wheels with a different offset from the rears to help counteract the width of the walking beams attached to the rear axle. The front end is slightly narrower than the rear end, but not significantly.

Awesome articulation :)

img33435_14042013183422_5.jpg

Next I built a transfer case as i wanted the truck to be a proper 6x6. I went with side by side input/output shafts, and produced a neat design using 2 0.8 module 20tooth motor pinions with a 5mm inner shaft diameter:

img33435_14042013183422_6.jpg

img33435_14042013183754_1.jpg

Unfortunately however, the side by side layout is not suitable as it leaves the UJs at a steep angle running to the axles, and the front drive shaft would foul on the 3speed gearbox. This means i now need to do another casing with an over/under layout, to reduce the angle of the UJs and provide clearance for the front drive shaft.

This is the latest progress on the truck:

I now have a bed made for holding logs. This is going to be fitted to the rear end of the truck so that it can be tipped up to provide easy access to the battery, which sits between the chassis rails.

img33435_14042013183754_2.jpg

Also the 3 speed gearbox has been mounted, along with the shift servo to operate the gear change:

img33435_14042013183754_3.jpg

A demo shot to show the rear suspension articulation:

img33435_14042013183754_4.jpg

and one more to show the light cluster fitted to the rear of the bed:

img33435_14042013183754_5.jpg

The trailer that the truck is going to tow, left over from a tractor build that will now probably not happen:

img33435_14042013183754_6.jpg

I should hopefully be making some rapid progress on this in the next couple of weeks, geting the bed fixed on, shorten the rear end of the chassis slightly, get the tow bar fitted for the trailer, and get the new transfer case built and fitted. I'll only need the steering servo fitted then before I can give it a quick test drive ....

  • Thanks 1

Share this post


Link to post
Share on other sites

Your builds are amazing. I wish I had a shop and the skills that you do with aluminum!

Cheers,

Skottoman

Share this post


Link to post
Share on other sites

Your builds are amazing. I wish I had a shop and the skills that you do with aluminum!

Cheers,

Skottoman

Thanks mate. I got a friend to do the welding for me though. I really need to get myself a TIG welder. Hoping to post some more progress on this project this weekend. Itching to get back at the king tiger gearboxes now though !

Share this post


Link to post
Share on other sites

as Skottoman said, you build some amazing stuff!

I'll be watching this with interest

Share this post


Link to post
Share on other sites

I love things like this, really clever and unique. Are you going to damp the movement of the walking beam?

Share this post


Link to post
Share on other sites

I love things like this, really clever and unique. Are you going to damp the movement of the walking beam?

Nope, the truck I based it on doesn't have any damping fitted as far as I could see. Top speed of them was about 20-25mph, so damping was not deemed necessary. It's going to be a heavy model when finished, so I don't think it will be bouncing about much anyway.

Been busy with it again today. Assembled the log guard for the tractor unit and brazed it onto the log frame. Not as neat as the welding job as I couldn't get the metal hot enough, but what I've done will be plenty strong enough. I've also fitted a 6mm shaft to the rear of the log carrier to enable the log bed to tip backwards and upwards, to enable easy access to the battery, which will sit between the chassis rails, to help keep the CoG down.

I've also shortened the rear of the chassis by 16mm, and added a basic tow hitch. I still need to improve upon the mechanism for connecting the trailer to the tractor unit, but this will do for now.

Here's some more photos. The next job will be to make hinge brackets for permanently mounting the log bed to the chassis, and painting the log bed yellow.

img33435_14042013184119_1.jpg

img33435_14042013184119_2.jpg

img33435_14042013184119_3.jpg

img33435_14042013184119_4.jpg

img33435_14042013184119_5.jpg

img33435_14042013184119_6.jpg

The suspension looks like it will perform really well over rough ground, keep the chassis fairly flat. Can't wait to drive it now, but loads more to do yet........

  • Like 1

Share this post


Link to post
Share on other sites

That is just so cool looking. Are you going to match the tires all around? I can't believe it's 6 wheel drive, but it most certainly is!

Share this post


Link to post
Share on other sites

Not at the moment. The back end is quite heavy with the log bed on it, so slightly firmer tyres will be better for the rear end, and with a load on there will be tons of traction. I need the different wheels on the front to widen the track to get it to match the rears, and the softer tyres will be better for steering grip, as with the trailer on I suspect there will not be much weight on the front axle.. I've got the log bed painted now and the hinges made to fix it in place, but I've run into a problem in that there is not enough length in the chassis to fit the transfer case between the gearbox and the rear axle. An F350 box would solve the problem, but I'm not prepared to fork out the cash for that. Currently I'm thinking that I am going to have to directly attach the transfer case to the rear of the gearbox, this will then allow enough room to get everything in. I think I may have to redesign the gearbox mounts as well. 2 steps forward and 1 back. This is turning into another king tiger build.......

Update 07/09/2012:

Finished painting the truck log bed and made the hinges recently:

img33435_14042013184448_1.jpg

img33435_14042013184448_2.jpg

Jumped in with both feet on attaching the transfer case to the gearbox. Used the pinions out of the original transfer case I made plus 2 I had left over from the shredded king tiger gearboxes.

I machined the bearing holes and have tapped threads ready to bolt a gear cover it. There's no other support for the attachement other than the 4 bolt points, but the backplate is 6mm thick so there's no way it's ever going to bend. The pinions can give a 25% reduction or increase in speed, depending upon the order in which they are fitted.

img33435_14042013184448_3.jpg

img33435_14042013184448_4.jpg

img33435_14042013184448_5.jpg

As an added bonus, a juggernaut2 drive shaft appears to be a near perfect fit for the front drive shaft:

img33435_14042013184448_6.jpg

Hopefully I will be getting the gear cover done shortly. Unfortunately once this is done I need to redesign the gearbox mounts as I need to raise the gearbox slightly.

13/09/2012.

Update, Got the gearbox mounts made today. On the first attempt to run it I got a nice rough sound coming from the gearbox. My first thought was that my home made transfer box wasn't meshing right and I had a problem. Further investigation revealed the grub screw on the motor pinion catching on the plastic spur gear inside the 3 speed. Added one of tamyias blue/green motor gaskets between the motor and the mount plate and now it's fine.

a (very) short vid of it running over a couple of obstacles.

No steering as yet, but the walking beams cope easily with obstacles. bear in mind that neither of the diffs are locked. Had some problems with the speed controller glitching whilst trying to film this which is why there isn't much of it. I think I might have a faulty transmitter as I had a similar problem using the trnasmitter on a different set of radio gear. Looking forward now to getting the steering finished so that I can load the truck and trailer up and see what it pulls a heavy load like off road :)

  • Like 1

Share this post


Link to post
Share on other sites

I can't believe it doesn't have locked diffs, but I assume with that many drive wheels, something is gonna grab!

So... are you keeping a total of the number of pinion gears you're using to make this monster?

It looks a bit fast, but I guess loaded up, it might crawl more?

Great work, I'm again amazed at how much stuff you fabricate!

Cheers,

Skottoman

Share this post


Link to post
Share on other sites

I can't believe it doesn't have locked diffs, but I assume with that many drive wheels, something is gonna grab!

So... are you keeping a total of the number of pinion gears you're using to make this monster?

It looks a bit fast, but I guess loaded up, it might crawl more?

Great work, I'm again amazed at how much stuff you fabricate!

Cheers,

Skottoman

The grip is excellent, isn't it :). I think it's all down to the suspension. Because the front axle is free floating and doesn't have springs, it's pretty much impossible to not have the full weight of the front end on both front wheels, unless you're grounded at some point on the axle tube, or one wheel is so far off the ground that the other won't touch at full articulation (it's got a lot of articulation in the front axle.). Many people use soft leaf springs on their scalers to get better articulation, I've just gone one step further and removed them completely. It does cause the front end to bounce a bit though. If you watch the vid in slow motion, you can see the front axle bounces right off the ground going over one of the obstacles.

The walking beams on the rear suspension also help enormously with grip as they are free floating. The whole axle is sprung, but the walking beams are free to float up and down without any restriction, meaning the weight of the vehicle gets spread more evenly across the wheels. Add to that the rear wheels are mechanically linked with the gears in the walking beams, and you get much better traction without resorting to diff locks. (You have to lose traction on both rear wheels on one side for the diff to spin).

My walking beams were expensive as I had to use aluminium for the cases and steel pinions for the gears inside, but it would easy for someone with access to an injection moulding machine (Cough, Mr T, cough, RC4WD, cough) to produce walking beam housings in plastic, and also to use plastic gears inside them. The walking beams do use 20 roller bearings though, so some extra expense there (An extra 10 bearings over using an extra axle). It would be easy way to convert a pickup to 6x6 without having to do any extra fabrication, other than chop the rear end of body to extend the wheel arches. The walking beams also have the massive advantage of far better articulation and grip than adding an extra axle, and not having to use a locked diff means better cornering as well.

Back to my build, It's got 14 pinions in, not including the one attached to the motor. :) I'm quite pleased that it is not too noisy, considering the amount of extra gears that I've added. I think that the aluminium cases for the walking beams and transfer case help to deaden any sound coming out of them. When I built the all aluminium gearbox for my Lunch Box 4x4x4 MK2 I was surprised at how quiet that was when I ran it.

The truck looks fast at the moment as I was having trouble controlling the throttle when I took the video. I was getting uncontrolled throttle inputs, which meant I couldn't feather the power in. I suspect it may be a faulty transmitter or speed controller. Having said that I was surpised at how fast it is considering I had bottom gear selected and I have a 1:0.75 gear reduction in the transfer case, I am using the stock 10tooth pinion on the motor, and I have an Ansmann 55turn motor in it. I'll be motoring on now with trying to get the steering fabricated, so that I can do a proper video. :)

Edit 15/09/2012:

I found that the transmitter was faulty. Unusual as this is the first time I've had this problem. The truck can now crawl very slowly under good control. I tried it pulling the trailer with a full load on and it makes the truck light on the front end due to the weight on the tow bar trying to pick the front wheels off the ground. I'm not worrying about it too much at the moment though as more weight will be going up the front when I get the body built.

Share this post


Link to post
Share on other sites

Just uploaded a very short clip of the truck pulling the trailer with a load on. This was done with a nearly flat battery, but it shows the truck is more controllable than in the first video.

[media=]

[/media]

Still have to set up the steering. Thought I was getting somewhere with it and then ran into a snag. Going to step back from it for a short while as the more effort I throw at it, the more mistakes I make and problems I'm finding. The first attempt at the steering blocked the shift lever, so I need to reposition the shift lever in order to give the steering maximum room.

I have now added some extra shocks to the rear end as the springs were too soft for the weight of the trailer. It's much better with these TA05 shocks fitted to the spring hangers:

img33435_24092012221447_1.jpg

img33435_24092012221447_2.jpg

img33435_24092012221447_3.jpg

  • Like 1

Share this post


Link to post
Share on other sites

Wow. I'll say that thing will probably drive over most anything. While you don't claim to have an attention to detail, you sure do have an attention to function.

Interesting solution to add the extra shocks to help the leaf springs out. Adds some dampening I'd imagine as well.

Cheers,

Skottoman

Share this post


Link to post
Share on other sites

I love reading your threads, you are a credit to this community, I couldn't even dream about making some of the stuff that you come up with. Can I ask what you do to make a living?, you certainly do deserve your username. With your engineering skills and Skottomans attention to detail, you could create some fantastic rc machines.

Share this post


Link to post
Share on other sites

Despite your frustrations that's an amazing creation. The shocks look like a neat fix and don't look out of place.

I can't see where you've positioned your shift linkkage and servo, but on my Tundra I moved the servo to the rear of the gearbox. Would that be an option on this?

Share this post


Link to post
Share on other sites

Wow. I'll say that thing will probably drive over most anything. While you don't claim to have an attention to detail, you sure do have an attention to function.

Interesting solution to add the extra shocks to help the leaf springs out. Adds some dampening I'd imagine as well.

Cheers,

Skottoman

Thanks. I have found that it gets stuck easily if it grounds out though. This is down to the low position of the transfer case and the size of the wheels. I might end up locking the front diff or putting a one way in it for a bit of extra grabbing power. If I lock the rear diff with the 2 rear wheels geared together each side it will never turn. I put the shocks on the end of the leafs as I didn't have room for a conventional vertically mounted solution. The oil dampers do seem to cut down on the bounce a little, which is good.

I love reading your threads, you are a credit to this community, I couldn't even dream about making some of the stuff that you come up with. Can I ask what you do to make a living?, you certainly do deserve your username.

With your engineering skills and Skottomans attention to detail, you could create some fantastic rc machines.

Thanks very much. In my normal job I'm a software engineer. I don't think Skottoman would put up with the ugly finish on most of the stuff I make. The only thing I've made that I've actually finished and am pleased with is my Lunch Box 4x4x4. It started off life as a TLT-1 and is now on it's 4th chassis redesign, 3rd gearbox, 2nd set of axles, and it's probably taken 3-4years to get right, on and off.

Despite your frustrations that's an amazing creation. The shocks look like a neat fix and don't look out of place.

I can't see where you've positioned your shift linkkage and servo, but on my Tundra I moved the servo to the rear of the gearbox. Would that be an option on this?

Unfortunately there is no room behind the gearbox as the battery is mounted between the chassis rails and I plan to be able to fit an 8.4 - 9.6V stick pack in there. The servo at the front of the truck in front of the motor is the shift servo, the shift rod runs inside the chassis rail. The steering servo is going to be side mounted against one of the chassis rails.

26/09/2012 - Progress today:

Had the day off work, made 2 new mounts for the shift servo, refitted it and verified that the shift now works smoothly. As the servo is now slightly higher, the parts I made previously for the steering now fitted ok without causing a problem to the shift linkage for the gearbox. I made the pivot arm for the steering mechanism. Nearly lost a finger trying to hand rotate a piece of aluminium round a rod to get a circular edge of a workpiece. The mill snapped it out my fingers and took a big bite out of it. (I'm still typing this with 2 hands though, so a fortunate excape). The part looks an aberation now, but is still functional so it's gone on the truck for the time being. I also made a steel sleeve for it to rotate on and a collar to hold it in place. I also fitted the RX and speedo in their final locations (for the time being). I dismantled both walking beams as there was some play in the rear axle and found a loose grub screw in the second one I opened. Retightened and reassembled and good to go now. The only tasks left to do now is to make a plate to fit the steering servo, and make up one track rod and I should be able to drive it. Hoping to be able to do this tomorrow and have a video of it driving around to upload :)

Share this post


Link to post
Share on other sites

Finally got the steering finished on the truck today and managed to have a quick drive with it with jus the trailer loaded :) No video as yet but here's a few more photos of the progress so far:

Fully loaded. Too much weight for one crawler motor ? We shall just have to wait and see ;)

img33435_27092012193546_1.jpg

Suspension still has movement in it, despite the weight on it.

img33435_27092012193546_2.jpg

Steering servo installation. Still need a block of ally at the top to screw the gearbox to.

img33435_27092012193546_3.jpg

Quite a bit of weight on the back end. The sidewalls of the rear tyres are just starting to bulge under the weight.

img33435_27092012193546_5.jpg

Here's a quick video of the front suspension in action. No bump steer despite the servo no being mounted on the axle. Pleased considering the articulation in one direction.

Hopefully I will be taking it out for a good trial run and video on Saturday. That's it for me for now on this project, the cab and lights are going to have wait for a while.

  • Like 1

Share this post


Link to post
Share on other sites

This.is.awesome!

Really, really awesome. But you need a video camera or SD card that can hold more than 14 seconds... :P

Share this post


Link to post
Share on other sites

Longer video of a run in the woods available here:

Got stuck several times but still good fun. Off road performance is pretty good considering the weight it is carrying and pulling. Needs more weight on the front end to get some traction on the front axle though. Hopefully the cab will provide this when I build it. I think it also needs a 9.6V battery and a motor with more RPMs. The weight on the load bed on the truck causes one side of the axle to lose traction easily when it leans over to one side. Not in the scale crawler performance category by any means, but a lot more fun than a king hauler on a bit of flat tarmac, and I think I could probably improve the grip in time. The trailer might case fewer wheelies if the tow bar was shortened, but that would mean rewiring the LEDs in the trailer lights, which would be a nuisance.

Hope you guys like it it, I do, the walking beams show enormous potential for off road grip (When I got stuck it was because the tyres were not gripping, not because they were off the ground). I'll hopefully finish the cab off on this and the lights, then put the ideas I've had from this model into the next idea.

Things I would do differently:

1. Ditch the 3 speed. It is really useful and needed in this model to get the weight moving on one motor, but it would have been better to be able to have the transfer case higher in the chassis, and then just have a more powerful motor, or multiple motors, so that the 3 speed is not required. This would tidy the design up considerably. The best option would be a smaller 3 speed gearbox running 2 motors for extra torque and a seperate transfer case. This was my original plan, but there was not enough length in the chassis to achieve this.

2. Angle the walking beams downward slightly to improve the ground clearance of the rear axle. Also angle the gears upwards from the pivot point, then back down at the wheel axle ends of the beam to help lift most of the walking beam higher above the centre line of the wheels.

3. Use bigger wheels and tyres. Lunch box rear wheels and tyres would have provided much more traction (Although not to scale). My walking beams are too closer together to add larger diameter tyres (Although double rear wheels might be an option !)

Am I the only one that thinks a 6x6 off road truck would be a good addition to the tamiya stable of 'rigs', even a 1/10 one like this ???? :) Would you buy a model like this with a nice plastic cab / rear bed for Hi-Lift money (Still plenty of room in the cab for a mfu :) )???

  • Like 1

Share this post


Link to post
Share on other sites
Hope you guys like it it, I do...

I do! A lot actually and thanks for posting that longer video, spills and all. Indeed the occasional spills and sticks make it seem more real. For the first few minutes I was thinking, 'will this never tip over'?!? It's good to see what it can handle and also what its limit is. It's certainly hugely capable which is a major credit to you.

Am I the only one that thinks a 6x6 off road truck would be a good addition to the tamiya stable of 'rigs', even a 1/10 one like this ???? :) Would you buy a model like this with a nice plastic cab / rear bed for Hi-Lift money (Still plenty of room in the cab for a mfu :) )???

Yes! But I'm sure it would be expensive. But how much fun it would be to build and bash a chassis like that... :wub:

Share this post


Link to post
Share on other sites

The trailer might case fewer wheelies if the tow bar was shortened, but that would mean rewiring the LEDs in the trailer lights, which would be a nuisance.

Moving the trailer axle forward so the weight is better balanced on the trailer will take some of the weight off the hitch, which will reduce the wheelies. You still do need some weight bias toward the hitch or it will work the other way and start taking weight off the truck axles (less grip).

Share this post


Link to post
Share on other sites

I do! A lot actually and thanks for posting that longer video, spills and all. Indeed the occasional spills and sticks make it seem more real. For the first few minutes I was thinking, 'will this never tip over'?!? It's good to see what it can handle and also what its limit is. It's certainly hugely capable which is a major credit to you.

Yes! But I'm sure it would be expensive. But how much fun it would be to build and bash a chassis like that... :wub:

Thanks :) I don't think it would be much more expensive than a high lift though. The aluminium parts for the front suspension could easily be incorporated in plastic into the axle moulds (minimal cost), there are no front leaf springs (cheaper), the oil shocks on the rear springs are cheaper to make than those nice F350 anodised red shocks, and the walking beams could easily be made with plastic casings and gears. I made mine from ally beacuse that was what I had to hand. (The heavy walking beams to help enormously with the centre of gravity though). There are the same number of axles / diffs / UJs, a F350 box could be used as standard, the only real extra cost would be an extra pair of wheels and tyres, and the gears and axles used in the walking beams. I don't think it would cost any more than an extra £20 - £30 over an above a standard high lift kit.

Moving the trailer axle forward so the weight is better balanced on the trailer will take some of the weight off the hitch, which will reduce the wheelies. You still do need some weight bias toward the hitch or it will work the other way and start taking weight off the truck axles (less grip).

That's a good idea Mark. The only problem is the main support for the trailer walking beams is TIG welded to the main spine of the trailer, and I don't think it will come off without some major destruction. Definetly something to consider for any possible MK II though. I also thought about shortening the towbar somewhat, although the problem with doing that is that the wiring for lights is already routed through the inside of the towbar .......

When I get time I will definetly spend some more effort on this truck, maybe some better rear tyres, finish (start !) the cab, a better speedo that has a decent reverse on it. It certainly shows the potential of the idea, but I might be better off finishing the cab and then starting on a MK II. Still very pleased that it ran ok and the transmission held up to pulling the extra weight

Share this post


Link to post
Share on other sites

I would have thought that grinding off the two welds, wire brushing some of the paint back and re-welding would have been easier than doing a cut and shut job on the tow bar. Either way will require some paint sanding and a touch up of the affected areas.

Share this post


Link to post
Share on other sites

I would have thought that grinding off the two welds, wire brushing some of the paint back and re-welding would have been easier than doing a cut and shut job on the tow bar. Either way will require some paint sanding and a touch up of the affected areas.

The tig welds go deep into the metal, so it would be more a case of cutting the axle support off and then grinding the metal back to flush on the spine. You're right though, the cut and shut on the tow bar will also be a pain. What I will probably do is get some scale chain to hold the logs on the trailer, and put some longer logs on the trailer to hang more of the weight off the end of the trailer. If I make a steel frame for the cab, this will also add considerable weight to the front (what it really needs is a RS750 up front to weigh it down :) )

Share this post


Link to post
Share on other sites

The tig welds go deep into the metal, so it would be more a case of cutting the axle support off and then grinding the metal back to flush on the spine. You're right though, the cut and shut on the tow bar will also be a pain. What I will probably do is get some scale chain to hold the logs on the trailer, and put some longer logs on the trailer to hang more of the weight off the end of the trailer. If I make a steel frame for the cab, this will also add considerable weight to the front (what it really needs is a RS750 up front to weigh it down :) )

How about a motor for 1:8 scale? They're about 750 sice AFAIK

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now