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MadInventor

New 6x6 build

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So I've decided to do a 'quick' project. I got hold of 12 rock crawler tires for free after an order for the War Rig tires go messed up a few years ago, so I thought I would do something with them. I spent a few weeks making up a set of dually wheels for 2 axles. After a bit of thinking I thought I would like to end up with another 6wd truck, similar to the 6x6 Scammel model I made a few years ago, but with some improvements. So after completing the wheels, I started a few weeks ago on this:

I ordered up some steel gears from China, and attached 12 tooth gears to a pair of modified Mad Bull axles.

SAM_1606.jpg

Then I took quite a bit of time to make these bits on the mill and the lathe

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Which can then be fitted to a King Hauler axle:

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and populated with the modified Chinese gears:
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which I turned the boss off and left a small 0.5mm collar to prevent the gear from rubbing on the aluminium plate. (I still need to order shims for the other side of the gears)
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Assembled and painted:

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With double wheels:
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Monster articulation:
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and a possible, but not likely end application, adding to my 4x4x4 Lunch box Chassis :)
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So, the things I like about this design are:

1. The walking beams on this are angled downwards, effectively making them portal axles as the drive axle is 20mm higher than the wheel axles. Also the walking beams have a 2:1 reduction ratio built in (common drive gear is 12T and final drive gears are 24T).

2. The axles are far enough apart to accommodate tires up to 108mm diameter.

The only downside is the weight. Anyone care to guess the weight of the sub assembly ?

I'm also getting a friend to 3d print a pair of spacer blocks to fit in between the aluminium plates to keep grit and dirt out of the drive gears.

More to follow once I decide how I'm going to proceed, but I know I'm going to use a pair of high lift chassis rails and a Hi Lift front axle, which means I need to build a transfer case with a 2:1 ratio drop for the front axle to ensure all the wheels rotate at the same speed.

 

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26 minutes ago, speedy_w_beans said:

Did somebody say gears?  :lol:  Watching with interest!

17-dec-002.jpg

Well I didn't want to be outdone by the GF-06 :). That aero engine looks a nice piece of work. What is it ?

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It's a Bristol Hercules 14-cylinder radial aircraft engine...  More info here.  Seems like something you would definitely enjoy!

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On 7/30/2019 at 10:34 PM, speedy_w_beans said:

It's a Bristol Hercules 14-cylinder radial aircraft engine...  More info here.  Seems like something you would definitely enjoy!

Radial engines fascinate me - how was it possible to not only come up with a working design, but actually makes these, back at the turn of the 20th century. 

@MadInventor - Martin, your crazy experiments with walking beams never cease to amaze, and your manufacturing skills are fantastic with just hobby equipment. 

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I've progressed (Well, done more work) on this over the last few weeks.

I initially used hi lift leaf springs to attach the axles to a 3 racing lightweight aluminium chassis I got cheap off Ebay  few years ago:

SAM_1650.jpg

 

I also finished off the transfer case:

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Machining the rounded curves on the casing. No CNC work here, all (very) old school.

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Mounted to one of the Hi Lift chassis braces

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With the outer case fitted

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Fitted in situ in the chassis

I then turned my attention to the steering, taking some inspiration from the Junfac kit that used to be available for the Hi-Lift:

SAM_1675.jpg

Home made servo bracket

SAM_1681.jpg

and aluminium track rods. I removed the heads of 20mm socket cap bolts to make the studs required to attach the track rod ends.

I then spent some time attaching the axles with a 4 link system. I initially used the Hi Lift surplus kit parts for attaching the links, but they are a loose fit on a King Hauler axle (which I used for the walking beam axle as it looked stronger and was cheaper that the hi lift axles), so I ended up making a couple of brackets myself:

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which are now a nice solid fit on the King Hauler axle:

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So this is the truck as it stands at the moment:

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The 4 link geometry is way off, the front axle is too close to the centre of the truck and needs to be move forwards, and the rear axle is also slightly too close as I didn't manage to replicate the dimensions of the Hi-Lift brackets exactly in my custom made ones (Got the mounting holes too close the axle by about 1-2mm). I also found that the axles pivot upwards when the suspension is compressed, which also needs to be resolved. So I now need to remake the side plates that mount the 4 links to the chassis, and / or possibly remake some of the 4 links with different lengths to resolve the pivoting issue. Once that is done there is then the small matter of making a reduction box to go between the motor and the transfer case.

 

 

 

 

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Nice bit of progress. Not without it’s problems, obviously, but nothing you can’t overcome. I don’t doubt that that’s part of the fun for you. 

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So, I haven't posted anything in this for ages, as I had problem after problem with it. I'm now waiting for a 3rd order of gears to arrive from China for the walking beams. The walking beams are going to be the MK4 version by the time this set of gears arrive <_<. In the meantime, I've finished off the main gearbox, which will drive the now re-designed transfer case (MK2 - like I said, lots of issues). I was lucky enough to get a friend of mine to 3D print the plastic insert that fits between the main aluminium gearbox plates.

Here's some pictures:

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SAM_1821.jpg

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So the MK4 walking beams finally came out ok. 

This was the basic plate. I've now got 9 gears each side, so that's 40 1150 bearings (The axles have 3 each) for the job.

SAM_1923.jpg

Layout of the gears can be clearly seen here. I used lots of smaller gears to keep the ground clearance up and the weight down as much as possible.

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Almost complete sub assembly. Just needs 3D printed seals to keep dust out of the gears now

SAM_1948.jpg

angling down the end gears allowed me to get an additional 11.63mm of clearance under the diff pumpkin.

SAM_1949.jpg



 

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So, I couldn't get the rear shock absorbers to compress without fouling the walking beams as they moved, so I made the decision to make a new chassis. Fortunately I'd kept the old chassis rails which weren't tall enough for the war rig trailer build, so chopped a bit off them to make 2 new chassis rails. I also decided to rear mount the motor & gearbox, which now sits slightly forward of the rear axle tube.

SAM_2015.jpg


SAM_2016.jpg


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Unlike the first truck I built with walking beams that had leaf spring suspension, this one has decent 4 link articulation on top of the excellent suspension movement the walking beams give.


 

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