6x6 Grand Hauler Tipper Truck

[Mad Ax 2090]

OK, so yet another new project started during lockdown.  Perhaps if we have a 4th or 5th wave I might get them all done...

I started this one because it was something I could do while watching films with my toddler on Wednesdays.  At least until I had to start doing tricky custom stuff in the workshop.  My daughter returns to nursery for the first time tomorrow and I'm back at work full time, so no more Wednesday build days - that's good, because every Wednesday I'd end up with yet another cut body to paint, or new built chassis to find a body for, or, in this case, built truck chassis to mess around with.

Anyway, the plan here is to build an automated tipper using a Grand Hauler chassis and day cab, Lesu tipper and electric lift assembly connected to the MFU's 5th wheel / remote leg actuator channel.  Like all big rigs this will be a longer project, but it's been good to finally make a start - the box has been in my bedroom for a few years now.

I haven't bothered to take a million photos of the build or the box or anything like that, if you're in here you probably know what a rig build looks like and there's a million other build threads if you don't.  This is basically a journal of the ideas I've had, problems I've come up against, obstacles I've overcome, sidestepped, ignored or been defeated by, and stupid things that have happened along the way.  There will no doubt be many.

So, here we begin: with yet another stupid diff rebuild.

Those of you who have followed my lockdown builds will see that I've been here before a few times over the last few months - all my TLT axles were built to crawl, so they were all locked.  This one seems to have been locked with some kind of solidifying putty.  It might be an axle I acquired built from someone else.  Either way, I had to prize it apart with a scalpel blade.  Not the best use for a scalpel blade, admittedly, but nothing else would slide between the gap.  After destroying a scalpel blade and nearly losing an eye, I used a screwdriver to get it the rest of the way open and a lot of brute force to get the innards out.

Now, as luck would have it (see previous threads on the subject), I already had some araldited diff internals sitting in a tub of IPA for around 2 months now.  They are finally dissolved enough to be cleaned by hand and reassembled.  These diff parts were damaged by a screwdriver tip while levering them out, but they're in the IPA cleaning themselves as we speak in case they can be repaired for another locked diff recovery later.

[Mad Ax 2090]

Next trick to assembling a 6x6 is mounting the front axle.  Fortunately the TLT donor axle already has a flat section with two holes in it - technically the axle is mounted upside down (the servo mount is now underneath) but looking at the output from the transmission, this is the right way to mount it (the axle will turn the correct way when using the output shaft from the front of the transmission).

I used the standard leaf springs.  My wife bought me a top-quality set of cobalt drills for our anniversary earlier this year, which were what I needed to drill some mounting holes through the leafs.  Sprung steel isn't easy to drill at the best of times, worse when there are several layers of it, and in the end my attempts to get central holes with a somewhat elderly drill press resulted in things going a bit off-centre, so they had to be re-drilled at 3.5mm.  That doesn't leave a huge amount of meat left in the spring, but it feels strong enough nonetheless, so that's what I've gone with.  I didn't really fancy trying to cram a 3-link or 4-link setup between those chassis rails along with the transmission, steering and prop assemblies...

The TLT axle is chunkier than a standard big rig front axle, so the front end sits higher.  I have seen other TLT-based 6x6 trucks that have got over this problem by ignoring it completely, but my tipper bed is all metal and very heavy, so the back end will need all the help it can get.  I don't want my headlights to be shining off the ceiling when it's got a full load.

[Mad Ax 2090]

First trick was to make some axle blocks.  I measured the height difference to be around 9mm between front and rear, so I used some 10mm alu bar to make the blocks.  A little extra height at the rear won't go amiss as it will level out once the weight of the bed is on.

It appears my camera did a brilliant job of completely not focussing on this shot, but here's the finished blocks mounted between the leaf springs and the axles.

There is however one problem - the lower are now too short, and are pulling the axles together.  This means I either need to extend the links or drop the lower bracket.  I'd usually go for making new links, but the angles are a bit intense and might affect the geometry, so my plan is to make all new lower link brackets (those V-shaped thing that bolts onto the chassis rails), identical to the current ones but bringing the bottom mount down by 10mm.  It should be a fairly easy job.  Some 1mm alu sheet has been ordered so I can do that next week.

 

[Mad Ax 2090]

The next issue was that of the steering link.  The leaf spring interferes with the standard straight link, so I needed to make a cranked link.  I started with some M3 stainless thread and put a threaded link over the end to protected the thread, then 'it it wi'ammer

[Mad Ax 2090]

The rod end wanted to hit the leaf spring when connected the normal way, so I crossed the cranked link to the other side, ducking under the gear servo.  There might be an interference issue here but the gear servo might have to change anyway - more on that later

 

[Mad Ax 2090]

Now - the transmission.  Originally I had intended to use a transfer box built and kindly supplied by @MadInventor, but I discovered a slightly neater solution using an extended output shaft from a German supplier:

https://www.der-getriebedoktor.de/en/enlarged-shaft-for-tamiya-3-gear-box

This allows a second propshaft to be connected to the front of the gearbox, thus saving me a bit of space, and allowing me to use the transfer box for something much more interesting later on.  However, having assembled the whole cabundle, I discovered a slight problem.

The standard gearbox location is far enough forwards that there ain't no UJ in the world will fit.  In fact it's almost close enough for a belt drive!  Actually a belt would be a neat solution, if it didn't need a tensioner assembly to take up the suspension movement.

The solution here is to move the gearbox backwards.  That's about as far as I got, because I ran out of time.

More updates sometime soon - although I'm not 100% sure when, because I am actually going racing next Sunday, so there will be no workshop day for me.  In fact I might be racing the following weekend too, pandemic notwithstanding, provided I can beat the rush and get booked in to the TORC Summer Series before the limited numbers are all used up.

Watch this space.

[MadInventor 2576]

On ‎6‎/‎29‎/‎2020 at 8:27 PM, Mad Ax said:

Now - the transmission.  Originally I had intended to use a transfer box built and kindly supplied by @MadInventor, but I discovered a slightly neater solution using an extended output shaft from a German supplier:

https://www.der-getriebedoktor.de/en/enlarged-shaft-for-tamiya-3-gear-box

This allows a second propshaft to be connected to the front of the gearbox, thus saving me a bit of space, and allowing me to use the transfer box for something much more interesting later on.  However, having assembled the whole cabundle, I discovered a slight problem.

The standard gearbox location is far enough forwards that there ain't no UJ in the world will fit.  In fact it's almost close enough for a belt drive!  Actually a belt would be a neat solution, if it didn't need a tensioner assembly to take up the suspension movement.

The solution here is to move the gearbox backwards.  That's about as far as I got, because I ran out of time.

More updates sometime soon - although I'm not 100% sure when, because I am actually going racing next Sunday, so there will be no workshop day for me.  In fact I might be racing the following weekend too, pandemic notwithstanding, provided I can beat the rush and get booked in to the TORC Summer Series before the limited numbers are all used up.

Watch this space.

Can I suggest having a look at this. It went in my showroom 7 years ago, it's a king hauler gearbox I modified for 4x4. it uses standard parts apart from a new backplate and a gearcover. The additional gears are standard pinions with a 5mm bore.

 

I got this a little close to gear cover and had to mod it slightly to keep it sealed, but the basic idea is sound. perhaps  3D printing a plate and a gear cover is an option ?  I could help out with the 5mm steel shafts if needed.

 

Edit: Sorry, just re-read this and saw the bit about moving the gearbox backwards .........(facepalm)

 

 

[Mad Ax 2090]

That's a very interesting setup @MadInventor, a very neat job.  So I suppose that new backplate is machined to fit and the output rotation is reversed, so the axles need to be flipped?

I like the idea and I can see how the propshaft will fit much easier, I'd be tempted to employ your services but I spent a fair bit of cash on those extended output shafts.  Postage from Germany cost as much as the shaft, so I actually ended up buying two of them for a possible later 6x6 project, before I realised how bad the prop angle would be.

Anyhoo - I'll either resolve this one by moving the transmission or employ that transfer case you gave me after all, but if I do another 6x6 I'll definitely consider the above idea  

[Randylandy666 1]

To throw another option into the mix, I used an Axial transmission and a 5mm pinion gear to give me a 2.7:1 reduction transfer box on my King Hauler 6x6
Here are the pics of the casing i designed:
https://stegs4x4.co.uk/product/tbox-tamiya3speed/

[MadInventor 2576]

8 hours ago, Mad Ax said:

That's a very interesting setup @MadInventor, a very neat job.  So I suppose that new backplate is machined to fit and the output rotation is reversed, so the axles need to be flipped?

I like the idea and I can see how the propshaft will fit much easier, I'd be tempted to employ your services but I spent a fair bit of cash on those extended output shafts.  Postage from Germany cost as much as the shaft, so I actually ended up buying two of them for a possible later 6x6 project, before I realised how bad the prop angle would be.

Anyhoo - I'll either resolve this one by moving the transmission or employ that transfer case you gave me after all, but if I do another 6x6 I'll definitely consider the above idea  

I machined the backplate to fit, it also gets rid of the need to use the plastic inserts to hold the bearings. Axle rotation is the same, doesn't need to be reversed. I haven't pictures of it but I made an aluminium gearbox cover to keep dirt out of the gears, that's what the 2 extra holes in the backplate are for.

[Mad Ax 2090]

Another quick update - there was a problem with my ebay order for alu sheet, so I haven't made the rear axle bracket yet, but I did have a spare day in the week when I managed to fit my tipper bed.

I managed to fit this without the Lesu tipper bed rails - the tipper pivot nicely fits into the last hole on the stock chassis.  Note that the rails have not been changed at all in this pic - this is a standard Grand Hauler length with a chopped day cab.

[Mad Ax 2090]

Not sure when I'll have time to do any more work on this rig - I'm pretty busy with racing and prep over the next few weeks so I need to put this one away somewhere safe.  Fitting the tipper mechanism seems a little trickier than I first thought as there is no mounting point for it on the tipper bed...

[ACCEL 754]

use a scissor type hinge

[MadInventor 2576]

That's looks really nice, especially considering it's stock chassis rails and a stock rear bed. Have you given any thought to using either Hi lift or Juggernaut leaf springs for the rear end rather than axle blocks ? They are a taller spring giving more ride height and are much stiffer than the standard truck leaf springs (Should you decide to haul wet sand in the back). I have both springs, if your interested I can remove them off something and measure the lift they give......

 

[Mad Ax 2090]

@MadInventor that is a good point.  Having fitted the bed to the back, it already looks to be sagging a little.

As I'm sure you know, the rear leafs are fitted "upside down" compared to a single-axle installation.  Do you know if the Jug / Hi-lift springs have same fitment, or would they need to be modified?

The lift measurement would be helpful - it might be that I would need a mix of lift blocks and stiffer leafs to get the correct height anyway

[MadInventor 2576]

4 hours ago, Mad Ax said:

@MadInventor that is a good point.  Having fitted the bed to the back, it already looks to be sagging a little.

As I'm sure you know, the rear leafs are fitted "upside down" compared to a single-axle installation.  Do you know if the Jug / Hi-lift springs have same fitment, or would they need to be modified?

The lift measurement would be helpful - it might be that I would need a mix of lift blocks and stiffer leafs to get the correct height anyway

When I finish work, I shall crack out the camera, screwdriver, and calipers. I'll let you know shortly (For me that's in the next couple of days). When I build my 6x6 truck as a log hauler, I had to add a TT-01 coil over to each side of the read to help cope with the extra weight, and that used stock 1/14 truck springs.

 

[Mad Ax 2090]

Thanks @MadInventor, that would be awesomely helpful

I'm also seriously considering going back to your transfer box, as relocating the transmission is going to be a bit of a pain (especially as I have to house a lifter mechanism under the bed and an MFU under the day cab (which is never easy).  I'm considering switching to a single-speed planetary reduction box, as I did on the Drag King project, to get a bit more space.  I don't really need a 3 speed box on this rig (the MFU-1 still gives the illusion of 3 speeds by restricting the power through the gears, as I discovered when testing it on my Globe Liner), and not having the terrible lash from the Tamiya transmission will be nice.