Scale RC Forum Forum Members’ Builds Off-Road builds My first build – D90 custom chassis (pic heavy)

This topic contains 5 replies, has 2 voices, and was last updated by JUNGL1STM4SS1V3 4 days, 2 hours ago.

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  • #104797
    Member
    JUNGL1STM4SS1V3
    JUNGL1STM4SS1V3
    • Looking For Mud

    So, this will be my first scaler and first build.

    I came back into the hobby a few months before Xmas with a 10+ year old AX10 I found in my parents shed.

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    This is actually a few weeks after I first got it running again, bought some new tires (HB rovers, huge!) and a new shell as my original shell blew away one day…

    Anyway, I knew I wanted a Defender, I have always loved the shape so I decided I would work towards building one. The Gelande 2 is a great looking kit but damn it’s expensive (10 years ago my full carbon and aluminium 1/10th TC was under £300 as a rolling chassis, I havent come to terms with the new pricing yet).

    So, the AX10 had its final run a few weeks before Xmas, it got a good drive off into the sunset.

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    Now it was time to start planning what parts to keep and what to buy.

    After stripping the AX10 down I decided the only thing worth keeping was the transmission and the prop shafts.

    I knew the basics, I needed axles, wheels and tires and a body. I could make the rest and it would give me a good excuse to get some new tools here and there.

    My first score from Facebook was these.

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    Chinese no brand aluminium axles. Slightly narrower than the AX10 axles, same mounting points and 4 link. Would rather they were black but beggars cant be choosers…

    Next up, I got some wheels and tires.

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    No idea what brand these are, the wheels are steel stamped and the tires feel decent but they’re not as soft as the rovers or the hammers I had previously. Again, a Facebook score.

    Finally the shell. I was moments away from buying a new lexan shell (probably the proline 4runner) and giving up on the dream of a Defender when I found this on Facebook.

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    I had assumed a Defender hard body would be out of my budget but I managed to get this for £30 delivered… I assume it’s a knockoff, the guy didn’t know, he got it in a job lot and had no use for it. Either way it looked great and there was nothing missing so I snapped his hand off. Only fault I can see on it is the roof windows are not great mouldings, other than that it seems identical to the RC4WD, although I have never seen one in person.

    At this point I hadnt fully worked out how I was going to build the rest of it and I was quite excited to paint the shell so that’s what I started to do.

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    I then decided this was the best point to cut the arches back… I ordered some ‘bolt-on’ arches at the same time, but we’ll get to that later.

    I knew the roof, arches, sills and other details would be matt black, so I got on with that in my makeshift paint booth.

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    I wanted the standard LR green, but halfrauds dont stock it apparently, but they did have British Racing Green, from Rover, which is pretty close. I did a test on an arch cutoff, one side backed with black, the other just primer.

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    Please disregard the thumb…

    Anyway here’s how the colour turned out

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    So it’s a lot darker than I wanted it to be, but it is what it is. Lesson learnt – if you want a certain thing, find a way of doing it instead of settling for something else. I have since found a local paint supplier that will mix custom rattle cans, so now I know for next time. All in all I think it still looks good.

    Anyway, then I built a crappy table in the shed to tackle the next stage, fabrication.

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    Obviously my excuse is everything fell off the wall just as I was taking the picture. Maybe I should tidy up and I wouldn’t have to build new tables…

    Next up, Part 2: The trials and tribulations of metalworking in a shed.

    #104800
    Member
    JUNGL1STM4SS1V3
    JUNGL1STM4SS1V3
    • Looking For Mud

    Part 2

    Next up is chassis. I decided on steel both for weight and price, also it’ll eventually rust like a real Defender…

    Firstly I drew around the bottom of the shell onto a piece of paper, marked the interior, body mount holes, wheel centres and shock positions and then sketched the basic shape of chassis rails onto it.

    Then I looked into steel and realised my largest option in 3mm flat bar is 50mm, and the chassis I drew was 55mm in height, so I resketched a new one over it and the whole thing became a mess.

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    A quick once over with a sharpie and it’s a lot more readable.

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    I took some measurements, marked them on and took this photo for reference.

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    Yeah, I should probably get on with learning a CAD package…

    Anyway, I cut it out and stuck it down to the 3x50mm flatbar.

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    I clamped 2 pieces together and drilled the body mount holes 3mm so I can locate them together and work on them together. Now time to go to work with the angle grinder.

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    Tedious work cutting many slots into the steel before cutting each one off. I don’t have any other pictures of the process as it was freezing outside!

    I got to this point the first night, got a bit too close to the line in places, I need some more practice with a grinder.

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    Maybe I was just shivering too much.

    I got to work on them the next day and got them pretty close, the glue didn’t last long on the paper so my line was a bit… not there in places, so they’re uneven in areas but they’ll do the job. I did go back and clean them up again after this.

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    With the rails pretty much done I started to look into making a skid plate. I still had the AX10 skid that the transmission was still bolted to but it would make the chassis too wide. The shock mounting positions on the axles meant that the chassis would have to be around 10mm narrower than the standard car.

    I initially decided on 6mm aluminium plate. This gave me enough thickness for M3 mounting holes in the side and should be easier to tap than steel.

    I ordered this piece of 100x100x6mm plate.

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    I cut myself a piece I think 65x45mm on the bandsaw and started to drill…

    **********

    I got through the 4 transmission mounting holes fine, but the side holes…

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    Yep, second hole, snapped a drill, deep.

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    This 6082 T6 is apparently really gummy and bad in all forms of drilling and machining. Turns out I needed to be using coolant, which I’m not setup for on my sub £100 machine mart drill…

    So, back to steel, something I know how to drill.

    I found a local steel merchant that agreed to let me go and have a look at their offcut shelf and managed to get a piece of 50x8mm steel flatbar around 130mm long for £2

    I hacked off a piece with the grinder and squared it up on the sander. It’s a bit wider than the aluminium version but that won’t be an issue.

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    I didn’t get any pictures drilling this piece as it was snowing and the shed was -2, it was a gloves on affair. However the drilling went fine, much easier than the aluminium.

    Until…

    I guess most on here know about tapping holes, and how one might go about tapping a blind hole. You need a bottoming tap, and the other 2 taps to start it. This turned out to be something not readily available in M3, and not cheap!

    After about a week of searching and ringing obscure engineering suppliers I managed to find someone to sell me a set for less than £20, he did me some standard 70% discount and brought it down to £7. Great, right? Scored a great discount and now I’ve got the tool I need?

    Well yeah, you guessed it, I snapped the special tap…

    The most frustrating moment to date on this project.

    Didn’t feel like going back the same day and asking for the same discount. I had enough steel to make a second skid plate but I still didn’t have another M3 bottoming tap.

    After a day of thinking I decided to drill another hole offset in the skid and go from there. The plan was to drill it deeper and go as far as I could with a 2nd tap. I had 3 holes at full depth threaded so I figured it would be OK if I had to use a shorter screw in the last hole.

    I didn’t get any pictures again for this, I just wanted to get it over with at this point.

    I figured the next step would be body mounts, I can get the chassis centralised in the body and start taking measurements for links.

    For this I ended up back at dreaded aluminium. At this point I figured tapping tiny, deep holes in steel was a harder and more expensive endeavour than learning how to drill aluminium at home, since aluminium taps like butter.

    A local crawling group on Facebook had the answer, a guy on there who works with machining 6082 told me WD40 might work well as coolant.

    I was using 6mm square bar for the body mounts, which came in 2m lengths, and I had loads of 2.5mm drills at this point and a full can of GT85, so I set out the experiment. I set up my vice in a repeatable centre position, covered everything in a rather fetching sheet and cut a few blanks the right size for body mounts.

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    I apologise the action in this photo is out of focus but it was kinda hard to use the GT85 and take it at the same time.

    If you can make it out, the square bar is clamped on end and I’m spraying the cut with GT85 with my left hand and operating the drill press with my right.

    Turns out there was no need to experiment, this method works a charm and I could drill extra deep holes with ease meaning I could tap with the 2nd tap and not worry about a new bottoming tap.

    Anyway, enough about tapping… Here’s the chassis assembly mounted in the body

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    Seems to work well and wont interfere with steering. As you can see by this point I have drilled the new steel skid for the transmission, I did this by clamping the original skid to the work piece and drilling through on the drill press. I decided to counter bore the holes for cap head screws rather than deal with my s***** counter sinks, also it looks way cooler. You can also see where I had to drill a new hole on one side very close to the transmission mounting holes, the bolts are not symmetrical on both sides. Also the whole transmission is shifted towards the rear for the benefit of interior mounting. I haven’t finished modifying the interior yet but to avoid cutting out the entire centre console, the transmission must move rearward.

    Here’s how it sits in the body before everything else goes in.

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    I think the chassis rails sit slightly lower than intended at the front and rear which may make bumper mounting a bit awkward. But all in all it’s in and vaguely resembles a chassis.

    Next step, Part 3: suspension

    #104802
    Member
    Grasshopper
    Grasshopper
    • Scale Off Road Pro
    • ★★★★★★

    Haha, that’s an epic start, thoroughly enjoyable read! I had a great picture in my head of you unsuccessfully chasing a lexan shell across the the dales in the wind!

    The shell you have is a standard Chinese D90 shell, even the RC4WD ones are the same. I’ve had three or four now (including the Gelande 2) and the only difference I found is that one of them was in a much brittler plastic than the others – I guess it’s just luck of the draw though. £30 delivered is a good price, same as you’d find on Ebay.

    I like the way you cut the wheel arches down, looks really good.

    I’ve got an Axial SCX10 with that D90 shell on and there was a fair amount of the interior I had to cut away to accommodate the Axial transmission. I’m guessing it’ll be similar with an AX10 trans too.

    Looking forward to seeing more

    Axial SCX10 Dingo    RC4WD TF2 Hilux     RC4WD G2 D90     WPL C14

    #104807
    Member
    JUNGL1STM4SS1V3
    JUNGL1STM4SS1V3
    • Looking For Mud

    Thanks Grasshopper! I do like to write a bit I admit. The sad thing about the shell blowing away is I didn’t even notice it. I popped a prop shaft back on and turned around and it was gone.

    I think I might have gotten a decent shell then as it seems plenty flexible. I haven’t used or really seen a hard body before so I have no frame of reference, I know I’m going to have to be a lot more careful with this on the rocks than I have been before.

    I worked on fitting the interior today and I think I’ve gotten away with it mostly from moving the transmission back and canting the rear shocks forward slightly. There’s still plastic removed from the centre section for the spur gear but it hasn’t ruined the interior. Enough spoilers for now though, I have to get on with the suspension post.

    #104809
    Member
    JUNGL1STM4SS1V3
    JUNGL1STM4SS1V3
    • Looking For Mud

    Part 3: Suspension

    This part had me stumped for a while, I didn’t really know the best way to take measurements for the links. I knew the shell wheelbase  was 280mm but I needed the shell off to take the measurements and then I had no reference for the wheel arches.

    I toyed with the idea off a WB jig, just 2 plates parallel to each other, each with 2 holes 280mm apart. You can mount the axles at the correct WB, align all the other parts with it and crack on with measurements.

    However…

    I realised while mocking everything up like this:

    IMG_20190203_152218

    That I could just turn the whole thing upside down and the arches and tires would keep the WB about right.

    I knew I was making the links with M4 stainless allthread and 6x1mm aluminium tubing. I decided on RC4WD M4 M3 long rod ends for the build.

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    This was the second batch of tubing, the first 2m piece I ordered from AluminiumWarehouse and it was completely out of spec, no chance of fitting M4 rod through. Good old B&Q saved me in the end though.

    I took my measurements by attaching a rod end to each mount point either end of the link and took a measurement between them and cut 2 pieces of tubing at that length.

    I have made a few links in the past using this method but I wanted these to be neater than previous attempts. Here I devised my method. I cut the allthread with the angle grinder and the tubing on the bandsaw but these produce rough cut finishes.

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    I’d much rather do these on a lathe, but I don’t have one. I do have a drill though…

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    And the tubing got squared up first before being chucked.

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    And this little Stanley vice is a god send for things like this.

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    Easiest job so far I think.

    I left the upper links without tubing for now as I want to fine tune the angle of the axles when the car is mechanically running a weighted up.

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    Notice how with the tires in the arches, at full extension the links are just shy of the body mounts. This of course was by design and totally intentional…

    I had to swap the link and shock positions from the above pictures, the shock would catch on the chassis with springs on. For this to work I also needed to space the other end of the links from the chassis. I did this with a standard M3 nut between the ball joint and chassis plate, I’ll replace this with a proper spacer when I find the right material to make some.

    Now the shocks. I had to make shock towers and then decide where the right height for mounting would be.

    I cut 4 pieces of 50x3mm steel flatbar, the pieces measured 30x50x3mm. Once bolted to the chassis I had to find the lowest ride height.

    I cut a piece of wood that once placed under the centre of the car, the arches were just clear of the tires. I neglected to photograph this process, but I think its fairly self explanatory.

    Once I had my lowest ride height locked out, I could remove the shell, remove the springs and full compress the shock, placing my scribe through the top mount I could then arc a line onto my new shock mounts. I thought this was quite a dodgy way of doing it but surprisingly it worked out great. I canted the rear shocks forwards to allow for proper body mounting and once the holes were drilled I shaped the mounts up to look nice.

    Some pictures of the finished pieces.

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    And mounted.

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    Really happy with the finish on these. Once the car is complete I want to strip it back down and paint all the steel parts black including the links. At least once it rusts it’ll really look like a Defender underneath.

    Next up I deal with steering and ride setup.

    #104810
    Member
    JUNGL1STM4SS1V3
    JUNGL1STM4SS1V3
    • Looking For Mud

    Oh yeah, thought process behind shock choice: Thought I wanted 95mm, I was wrong, 80 would be better. These particular ones because cheapest modelsport had, I’m on a budget…

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