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MadInventor

Scratch built 4x4 tractor

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Made the underguard today. 1.5mm steel plate.

Flared up sides hopefully will stop bowing and flexing.

SAM_3632.jpg

Flared up rear end. As you can probably see, this was not a precision job, I just clamped in the vice and then hit it with a hammer.
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Gearbox sits nicely on it, and the underguard forms the bottom of the gearbox cover.
SAM_3635.jpg

Starting to look like a RC model now, rather than just a collection of parts. 1/4 scale servo is going to be mounted behind the motor, to operate the steering.

SAM_3634.jpg

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Done a bit more over the last couple of days. I've made the left hand side plate (Well sized it enough to get it on the tractor). 

Temporary fitment of electronics to the side of the chassis

SAM_3636.jpg

Long steering track rod helps minimise bump steer, another home made item.
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1/4 scale servo for the steering
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This has meant that today I've been able to test drive it in the garden for the first time with working steering. I have to say that I'm very pleased with it so far. I can only get about half the steering lock due to the short throw on the steering servo, but the long lever on the axle end of the steering means that moving the steering whilst stationary is no problem. Even with the lack of steering lock the turning circle is very small, thanks to the wheels being so close together (I think they are set at 208mm from the centre line of the front axle to the centre line of the rear axle.

There's obviously loads more work to do on it still, the left hand plate will need trimming down for a start and some spacers made to properly attach the rear bulkhead to the chassis side plates. I might end up even remaking the left hand plate as the servo is a little higher than is necessary. But it's nice to be less than 3 months into a build and to have what appears to be a mechanically reliable, robust model, that I now only need to do cosmetic work on. Of course, that will probably end up being the majority of the work, but at least with that I don't need to make sure that it's accurate to within a few hundredths of a mm.

:)

 

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On 5/27/2022 at 3:58 AM, Nikko85 said:

Amazing work. What's the weight of it?

 

Heavy, I'd say about 5kg at the moment, but I am planning to carry out a weight reduction exercise once I get further into the build and am confident that I can machine away excess metal. That said, I don't expect to remove more than about 0.5Kg from the final model, and I still have a fair bit more weight to add yet with the addition of the bonnet and nosecone structure, and also mudguards, with the possibility of a cab. A lot of the weight is in the steel gears, and also the thickness of the metal in the front axle.

Part of the reason for building this was to prove to myself that it could be done in such a small package. I've been saying on here for years I'd like Tamiya to build a 1/10 scale 4x4 tractor that wasn't a 'comical' type speed machine like the farm king, but a model with scale speed / suspension that looks like a proper tractor, and has a diff lock into the bargain. I've proven it can be done, and it only took 3 months to design and build the chassis, so for a big company, a similar offering plastic at a fraction of the weight shouldn't be too difficult, should it.............

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1 minute ago, MadInventor said:

Heavy, I'd say about 5kg at the moment, but I am planning to carry out a weight reduction exercise once I get further into the build and am confident that I can machine away excess metal. That said, I don't expect to remove more than about 0.5Kg from the final model, and I still have a fair bit more weight to add yet with the addition of the bonnet and nosecone structure, and also mudguards, with the possibility of a cab. A lot of the weight is in the steel gears, and also the thickness of the metal in the front axle.

Part of the reason for building this was to prove to myself that it could be done in such a small package. I've been saying on here for years I'd Tamiya to build a 1/10 scale 4x4 tractor that wasn't a 'comical' type speed machine like the farm king, but a model with scale speed / suspension that looks like a proper tractor, and has a diff lock into the bargain. I've proven it can be done, and it only took 3 months to design and build the chassis, so for a big company, a similar offering plastic at a fraction of the weight shouldn't be too difficult, should it.............

That's not as much as I may have thought, but that's aluminium for you. It looks incredible. 

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Nothing much, just a bit more tinkering. It surprising how long all these little mods take.

Made 2 of these spacers to fit between the rear subframe and the chassis plates. Also drilled out 2 of the 3mm holes and tapped them with an m4 tap, as it was awkward getting the nuts on the back when trying to assemble it. (I'd errorneously drilled them with 3mm holes rather than tapping them with M3 threads when I first made them.
SAM_3640.jpg

Drilled and tapped 4 more holes in the centre block of the gearbox. Also machined off some of the excess metal from it
SAM_3641.jpg

Also made a collar to fit over the rear centre drive shaft to help stop it splitting. I was a bit concerned about it as I'd shortened it, which had weakened it. But then again, it is 'Traxxas Tough' and I'm only using a single 540 motor.
SAM_3647.jpg


SAM_3648.jpg

Turned down the edge to match the drive shaft to make it look nice.

SAM_3649.jpg

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I haven't posted anything on the build for a while, things have not been going to plan................

To get to this:

Front-end-without-grille.jpg

I just couldn't seem to get the side plates right. Firstly I used the metal I was going to use for them for the underguard by accident. Fortunately my Dad was able to supply me with some suitable scrap metal. I then made 3 more. It was only when I got to making the front grille and fitting it that I realised it was too low and the nose was too short, so I then had to make 2 more. 

The mistakes...

Mistakes.jpg

So over the course of this week I  managed to make 2 more , which this weekend has finally got me to here

front-end-with-sloped-sides-on-the-bulkh

Side-View.jpg

The old headlights are from a 3 racing 5 bar light unit. Once I've painted the front grille frame I shall silicon them into the grille

top-view.jpg

So today I have made a mesh for the grille

Front-end-with-grille.jpg

I can't decide whether to paint the grille or not. I like some colour on it, but the paint makes the holes smaller. My son thinks to leave it as natural metal, so that is probably what I shall end up doing.
Painted-sample.jpg

Finally, I machined some weight out of one the front axle bulkheads by pocketing the back side, and also machined the sides down, chamfered the bottom of it to match the slope of the underguard that will go up to the bottom of the front grille, and drilled and tapped two holes in the bottom for holding on the underguard, when I get it made.


Underside-view.jpg

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More changes over the last couple of the last couple of weeks, but am not really much further forward than the last post.

I'd started on thinking about mud guards when I realised that the steering servo was up so high that it would take up a lot of the cab.  The rear end looked very blocky and basic so I thought I would refine it a little, whilst making room at the same time to move the servo forward and down, tucking it under the motor.

Here I've machined off the top of the rear of the frame, to bring it in line with the top of the servo mount recess. I also machined out the hole for the servo lead, and replicated it on the other plate on the other side. I also drilled and tapped from bolt holes lower down for the top of the rear support plate.

Diff-Frame-Rear.jpg

Up front I machined down the front of the plate, machined the top off the cross member and removed some excess metal from it, and drilled and tapped holes lower down for the top mount holes. I also machined some excess metal from the side plates by putting oval holes in them.

Diff-Frame-front.jpg

I also took the opportunity while everything was in bits to turn some excess metal from the rear axle mounts, making them look a bit more like the front axles.

Assembled-rear-end-with-turned-down-rear

All this work enabled me to move the servo forward and lower....

New-Servo-pos.jpg

This meant making new chassis plates for both sides. One of them was only temporary as it was full of holes, but it was a bit of waste having to chuck the right hand plate. I did try to save it, but messed up when I was cutting it to the new size. Not shown in pictures are the 2 new spacers I had to make to take up the gap between the chassis plates and the rear diff frames, I used the one on the right as one half of the servo mount, and made a small mount to bolt to the right hand chassis plate to  hold the other side of the servo in place

New chassis plate for the right hand side

Right-hand-chassis-plate.jpg

New servo mount

Servo-mount-1.jpg

Servo in its new position.

installed-servo-1.jpg


installed-servo-2.jpg

So quite a lot of work for not much perceivable progress, but I'm now happy to start work on making the mud guards, and some kind of floor for the cab.
 

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Made 2 clamps that fit around the rear axle. Got horizontal threaded holes that I can screw the mudguards to. These allow me to attach stuff to the rear axle without having to drill holes in the axles. I did this because you can guarantee that if I drill holes in the axles the first attempt will be in the wrong place. With these I can adjust where the mudguards attach without having to damage the axle tubes. I've no plans at the moment to put a 3 point linkage on it, but I could replace the lower parts of the clamps with something beefier that I could attach the lower parts of a 3 point linkage to.

Now I can start making mudguards :)

Mud-guard-clamp-1.jpg


Mud-Guard-Clamp-2.jpg

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Got one mud guard done, made from 0.5mm thick aluminium. Very low tech approach. Marked out with a square and a sharp pencil. Scored round the edges and flexed the aluminium sheet to break off the excess (just like cutting out polycarb shells). Then used a vice and a block of aluminium and a small hammer to do the folding. Then drilled the holes by eye with a hand held drill after drilling the vertical plate with the milling machine.

Mud-Guard-1.jpg

Mud-Guard-2.jpg

Left room to fit in a light bucket at the back of the mud guard.
Mud-Guard-3.jpg


Mud-Guard-4.jpg
 

 

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Got the right foot plate done. Put some slots in it so that I could the receiver in with an elastic band. I had to do this as I cracked the casing when trying to extract it out of a model I'd stuck it in with double sided tape. The elastic band retainer reminds me of holding the receiver battery box in Sand Rover :)

SAM_3843.jpg

SAM_3844.jpg
 

I've also painted the right hand mud guard and the foot plate with gloss white paint. It's not quite pure bright white but it was the best I could find.

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Spent some time on painting since the last update:

SAM_3854.jpg


SAM_3849.jpg

Headlights and grille are now secured in place.
SAM_3850.jpg


SAM_3851.jpg


SAM_3852.jpg

Note the slot machined in the bulkhead to allow the battery cables to pass through to the ESC.
SAM_3853.jpg

and also got distracted and put some new wheels and tires on my log trailer.  Replaced the old Brat front wheels and tires with TLT-1 wheels and tires kindly gifted to me by @Mad Ax

This might well end up being what gets towed around by the tractor, but I do need to replace the heavy duty tow bar connection on the trailer with something a bit more scale.
SAM_3862.jpg

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Tow Bar. Machined it from a solid lump of aluminium:

SAM_3866.jpg

SAM_3867.jpg

Out in the garden with the forestry trailer:

SAM_3868.jpg

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Works well. Tows the trailer uphill on 3S with ease. 


 

 

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This is some amazing work. Loving watch it come together! Can’t wait to see the finished article next to the forest one

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Started some work on the rear lights. I was going to use the rear lights off a tamiya flatbed trailer, but when I totalled up all the parts it was eye wateringly expensive, so decided to make myself some from scrap bits of aluminium. Below is the main part, there will be bits to bolt on the front to add coloured lenses, and a frame to hold it in place, and a piece of metal or plastic bolted to the back to stop the LEDs falling out. This is the first one, got one more to do now.

SAM_3880.jpg


SAM_3881.jpg

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Brilliant stuff 👍🏻
At least if the War Rig ever breaks down you will have something to tow it home with now. 😉

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Haven't posted anything on this for ages but have been working on it in the background. I have started making a cab frame (The brackets took ages as I had to make a jig for them and I made a mes of the first one). I also got the 2 ends of the exhaust made, just need to make a silencer to go in the middle to join them together with. The light buckets have been fitted and it now had working front and rear LED lights which are powered from the ESC supply to the RX.SAM_4057.jpg

SAM_4060.jpg


SAM_4061.jpg

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Did you bend the exhast yourself? Ive tried to similar for an old nitro car in the past with brass tube but either crushed it or couldnt get the bends to line up properly.

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1 hour ago, Superluminal said:

Did you bend the exhast yourself? Ive tried to similar for an old nitro car in the past with brass tube but either crushed it or couldnt get the bends to line up properly.

Yeah, I bent it myself. I bought 10mm steel tube from B&Q, polished it in the lathe, then used a draper miniature copper pipe bender that says explicitly on the box 'Do not use to bend steel pipes' :) I then cut the pipe roughly to length after the bend and then finished it off by machining it parallel to the main pipe with the milling machine. If you look closely you'll be able to see that the pipe is actually in 2 pieces. 

The pipe does collapse if you try to bend it through too sharp an angle, I think I stopped at about 25-30 degrees.

 

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Cab frame 90% complete and roof plate done. Now ready for painting white

SAM_4115.jpg


 

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