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R/C truck in OO scale mk2


TurboSnail
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A new project now graces my workbench - adapting a Leyland FG to remote control. This thread will follow the build of the truck (assuming all goes well and I don't ditch the project in frustration) and please feel free to comment with ideas or your own projects as I'm certainly no expert on this (yet). I've done one R/C truck in OO scale before (the Atlas truck pictured), but this builds off it with (hopefully) more functionality and better features and control.

 

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I chose the Base Toys Leyland FG DA85 'cos it was cheap, and eye catching, and most importantly had a good amount of empty space inside it. While physically smaller than the Atlas truck, I should be able to package the R/C equipment a bit better having learnt from it. 

 

First order of business was to dismantle it, which was fairly easy.

 

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It had a dividing section in the middle, so I removed it with pliers - I think most of the interior will go too to make room for the R/C stuff. Not that you could see it anyway, I guess this is a part used in lots of models.

 

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Comparing it to the inside of the Atlas truck (I think it's an Albion of some kind, which escapes me for now), there is clearly less space, although some is wasted in the truck by the positioning of the drive and steering servos. If you want to know more about the Albion, see the video below.

 

 

I'll leave it there for now, after all, I've got a model to get on with...

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Time to test whether I'm being too ambitious again (answer: almost certainly yes). 

 

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The receiver and battery seem to fit ok, even with the voltage regulator - this is great as I was expecting to have to use a smaller battery. The receiver is tucked under the battery, the only concern here is being able to fit all the wires in place - should be enough space though. Moving on...

 

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I'm using a micro servo for to power the truck, and if my theory and measurements are right, it should fit under the floor of the vehicle. This means it will be visible to the observer, but I think I can get away with disguising it as a fuel tank or something. This also makes the build simpler if the servo is part of the chassis.

 

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I think this will work... The other servo is for the steering and both just about seem to fit in the space between the wheels. The die-cast chassis and wheels will probably be thrown away, to free up space and also due to the problems I'd have making it steer and adding a drive gear to the rear axle. The wheel mouldings of cheap OO gauge vehicles tend to leave something to be desired in terms of detail and roundness - one of the issues I ran into last time was a wobble created by un-round wheels.

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Time to get into some more hardcore mods. A while back, I bought myself a Dremel, and have since been trying to justify it, but now I have found a good use for it! 

 

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The original plastic floor will form the basis of my chassis, but it needs to be flat to a) maximise the vehicle's ground clearance and b) be a good mounting surface for servos and axles. Cue Dremel, to grind off the raised detail you couldn't see anyway, as the truck body is lower. 

 

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I also had a go at the lower cab back area, to try and increase the clearance for the steering wheels as this was an issue I had on the last truck.

 

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Now I have a nice flat surface to work from and motorise, then the body should just drop on top...

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I'm using a servo to power the van, as there's really no other way to get a gearbox, motor and esc in as small a space as possible. I've modified it to rotate 360 degrees so it can be used as a motor - I've already written that process up as a blog post (click here to read) so I'm not going to repeat it here.

 

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So I need to pick a drive gear ratio... The previous truck I did had a servo drive, then a 2:1 gearset driving the wheels, giving a scale top speed of about 25mph. I want this one to be a bit quicker, maybe up to 40mph. As the other servo was a bit quicker, I'm thinking I'll gear the axle up by about 1.5x to compensate. I'd bought one of those multipacks of cheap plastic gears (58 for £2 seems like a bargain until you realise you'll only ever use 5 or 6 of them), so had a dig through and came up with a 16-tooth gear to go with the 22-tooth servo gear to give a ratio of 1:1.4, which is close enough for me. Looks like it will fit too, the gear has a 2mm smaller diameter than the driving wheels.

 

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The servo gear fouls the chassis if it is left flat, so the chassis was marked and drilled before joining up the holes with a file.

 

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Unfortunately, this is the moment I realised I was being a massive spanner, as with the gears being larger than I thought, having both servos within the van's wheelbase left me with almost no room to manoeuvre with the steering servo. Much more sensible to put it behind the rear wheels, out of the way. Cue getting the Dremel out again.

 

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I also tried using the Dremel cutting disc to cut the new hole for the servo gear - and discovered that they are completely useless. They also have a tendancy to shatter at high RPM, even if you're really careful and only cutting soft plastic, so I ended up doing it the old fashioned way.

 

Finally, the redundant hole gets plugged with plastic sheet, which I'm hoping will be at the right height to mount the rear axle to.

 

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If there is space inside at the end of the build, I'm thinking of making the blue lights on top flash - it's a fire truck so I probably have to by law... Anyway, in order to be able to make that upgrade, it needs space to mount some LEDs below the beacons to shine through, and I thought it best to make the holes now, before the bodyshell is assembled and varnished. I started drilling 1.5mm holes from the top (the same size as the beacons) and opened them up to 3mm from inside the shell to fit 3mm LEDs. Then (relative) disaster struck as the drill caught and pulled a chunk out of the roof on one side...

 

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Lucky this is an experimental model rather than a fully detailed layout one! Time to break out the filler, something I've never had much luck with in the past. 

 

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Sanded and painted, it seems I've managed to get away with it, although in the only example I've ever seen of a photo flattering a model, the colour match isn't quite as good as it looks on camera. Maybe we should all start using rubbish cameras to photograph our models... I might have to have a go at some light weathering to blend it in a bit.

 

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Not been making as much progress as I'd like to be recently, but I have managed to get the driver in...

 

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The back section of the interior is not needed, so was cut off to allow extra space for the control electronics. I had a dig around in my spares box to find a suitable figure, and after some surgery, he fits in the cab quite nicely. The cab 'glass' got a coat of paint at the back to disguise the now absent interior and the cab assembly is now ready to go in once the body has been matt varnished.

 

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An package arrived in the post yesterday from Poland...

 

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KKPMO is as far as I can work out one of the few places that sell a steering kit similar to the Faller car system one but without the magnet so you can steer it with a servo. They also do custom widths, so I went for 19mm between the wheels as that seems to suit the Bedford van. I also got a set of wheels and tyres for the front and rear axles, total cost about £10-15 depending on the ever-changing exchange rate.

 

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A quick coat of paint and a comparison to show the difference between the originals and the new wheels.

 

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Assembling the steering kit is pretty easy, it's only 5 parts plus a few pins to hold the wheels and axle on. This gives you a free-wheeling, steering axle with side to side articulation, so despite my reluctance to spend more that the van cost on some wheels, it is worth it for such a crucial part of the build. I've also attacked the steering arm with a file to decrease the turning circle as one of the issues with the last truck was the large turning circle, bigger than any of the road corners on my layout! Which raises questions about whether we put as much thought into making the road layout on our models as realistic as we do the track layout. 

 

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An package arrived in the post yesterday from Poland...

 

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KKPMO is as far as I can work out one of the few places that sell a steering kit similar to the Faller car system one but without the magnet so you can steer it with a servo. They also do custom widths, so I went for 19mm between the wheels as that seems to suit the Bedford van. I also got a set of wheels and tyres for the front and rear axles, total cost about £10-15 depending on the ever-changing exchange rate.

 

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A quick coat of paint and a comparison to show the difference between the originals and the new wheels.

 

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Assembling the steering kit is pretty easy, it's only 5 parts plus a few pins to hold the wheels and axle on. This gives you a free-wheeling, steering axle with side to side articulation, so despite my reluctance to spend more that the van cost on some wheels, it is worth it for such a crucial part of the build. I've also attacked the steering arm with a file to decrease the turning circle as one of the issues with the last truck was the large turning circle, bigger than any of the road corners on my layout! Which raises questions about whether we put as much thought into making the road layout on our models as realistic as we do the track layout. 

 

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Those new wheels are worth the expense, the base toys wheels are not the best and the ones you have bought look much more realistic.

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With the front axle built, it should be fairly simple to mount it on the chassis - I put two layers of 0.5mm plastic on first to raise the ride height to roughly the right height.

 

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Another nice thing about this particular steering axle is that it has two posts on the top that can be used to positively locate the axle rather than just guess. The chassis needs marking up with the centreline of the axle and the 2mm holes, which are 4mm apart.

 

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Test fitting the axle shows that the corners of the mounting plastic bit restrict the turning circle, so should be cut down. What you can't see in this photo is that the existing wheel arches in the chassis limit the articulation. 

 

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Once more with the Dremel to grind away some of the chassis around the wheelarches to allow freer vertical movement. The plasticard was cut down with a knife. I've left off permanently fitting the axle for now until the chassis gets a coat of paint. You can also see the test rear subframe in this shot, more on that another time...

 

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Onto the rear subframe - possibly too grand a term for it? The axle is made from a section of 2mm steel rod with the ends ground down to 1mm to fit the wheels. I did this with a dremel cutting disk, whilst turning the axle in a drill, thus achieving something both dangerous and stupid - I don't recommend it, and as you can see, it's far from perfect.

 

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Testing the axle for width then gave me measurements to use to build the subframe out of folded 0.8mm aluminium sheet. 

 

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Folded up, it looks like this. The kink in the top was to try and reduce the width slightly as it rubbed on the tyres - eventually I gave up on it and did what I should have done in the first place and made another one with the correct dimensions. I also took the chance to move the axle holes up slightly to reduce the ride height to the correct level. 

 

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The new one looks like this, shown here getting one of the holes adjusted to the right height by overdrilling and packing the edge with microstrip. It's a bit bodged, but I can't drill and fold very precisely with the limited tools available to me.

 

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Finally, the wheels and gears are permanently attached with superglue. The axle is held in a drill and slowly turned while glueing to make sure the wheel is on absolutely straight.

 

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The chassis got a coat of black, followed by matt varnish to hopefully stop the moving parts wearing through the paint. The competed subframe got the same treatment before being superglued on. The corners of the subframe were trimmed so they didn't show behind the wheels.

 

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Next job, lining up and fixing the drive servo. The microstrip you can see on the chassis is there to angle the servo up at one end, so the axis of the servo and the gear are aligned so it should run smoothly. Lining up was done by running the servo and holding it contact with the gear, and slowly moving it around until it meshed properly with no tight spots. Then glue whilst holding steady.

 

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Looking at the chassis from the side shows the approx. 2mm ground clearance - not much, but enough to be usable, or about 150mm in scale. Slow progress at the moment due to moving back to university and sorting out stuff (still haven't got internet yet, so I'm writing this from the Uni library, and getting some weird looks in the process).

 

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The front servo was test located first to try and find the best compromise between the actuator being central and the servo not being too close to one side.

 

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The steering axle then got the guide wire glued on - the 90 degree bend is there to make a bigger glueing surface and therefore more strength (hopefully). I would prefer to have a mechanical connection instead but drilling through the plastic would make it very weak. Doing it this way means that if, for some reason, the servo overextends or the axle jams, the glue breaks off rather than damaging the axle. In theory anyway, I've yet to find out if this actually works...

 

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The servo horn was modified by cutting a slit down the middle so that the guide wire could slide up and down (for the axle articulation) but not move side to side, which would allow play in the steering. I managed to screw this up, so I made the slot oversize and then added a piece of microstrip to get it back to the correct width.

 

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Finally, glueing the servo in place was done in much the same way as the drive servo, by holding it in place and turning it left and right until I found a sweet spot with no binding. 

 

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  • 2 weeks later...

Now the university term has started, my modelling time is severely restricted, but I have managed to make a start on the lighting system. 

 

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This is the r/c switch that I can connect to a normal channel and use as a 5v on/off circuit. The adapter will be cut up and attached to the flashing blue LEDs so that the whole system should be unpluggable (better word for that?). I'm also going to reduce the length of the wires on the switch so it has a better chance of fitting in the van - I'm not overly optimistic that it will, even with the reduced wiring.

 

Temporarily wiring the system together with the two LEDs in parallel with a 100ohm resistor in series with the battery (if that makes sense), it actually looks pretty good.

 

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Very good :)

 

I do like the amazing slow speed control you seem to have on the green lorry - using MikroModellBau motors and gearboxes is certainly easier in terms of installation, but you dont get that sort of slow speed accuracy.

 

What RC kit are you using?

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Very good :)

 

I do like the amazing slow speed control you seem to have on the green lorry - using MikroModellBau motors and gearboxes is certainly easier in terms of installation, but you dont get that sort of slow speed accuracy.

 

What RC kit are you using?

 

The RC kit is basically the cheapest handset-progammable controller I could find (FLYSKY/Turnigy i6) with the equivalent receiver (FSiA6, with the housing removed to make it smaller). The controller is actually pretty capable, with editable throttle maps (which really helps to tame the non-linear nature of the servos) etc., but it is pretty low build quality. The battery is a 2s with a voltage regulator inline to make 5v. 

 

The other downsides of the servo drive is they have a limited top speed (scale ~30mph) and are quite loud at full speed. But they are slower and cheaper than worm drive gearboxes, and don't require an ESC. 

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  • 2 weeks later...

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