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Mad Ax

Pole Trailer to Rigid Conversion

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My Tamiya big-rig history is long and convoluted and full of twists and turns, but this pole trailer is easier to explain.  It came to me a couple of years back when I had nearly finished building my Globe Liner as an "every man" rig (something I could take to truck meets and hand out to friends and new members for try-outs) and I needed a trailer for it.  A friend of mine had just scored an epic deal full of NIB kits, and one of them was a Tamiya pole trailer.  It wasn't really what I was looking for - I would have preferred a flatbed - but it was cheap and available for cash, and I could take it home that day (which made it easier to sneak into the house with the rest of my rig boxes).

It was only when I came to build the trailer that I realised it wasn't quite what I wanted.  My plan was to use an MFU-01 and remote trailer leg kit with the Globe Liner, but the pole trailer is an unusual double-articulated design and won't self-support when detached from the rig.  That meant it always had to be transported attached to the rig and can't be used with remote trailer legs.

Fast-forward a couple of years and my plans for my rigs have changed drastically.  The Globe Liner is now my chief favourite rig and is fitted with a Beier sound module.  I also have an IR trailer light kit for the pole trailer, and plans to make a remote leg kit that is somewhat tidier than Tamiya's crazily over-engineered solution.  However to make it work the pole trailer needs to be converted to a rigid chassis and be fitted with some form of leg.

First things first - here's the back-end of the trailer with the rotating pole carrier and the telescopic attaching bar removed:

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And here's the rear with the deck and light carriers removed:

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As you can see, beneath the deck the chassis is just some aluminium L section.  In this case, readily-available 20x30mm L section.  An order on ebay and a week for delivery and work could commence

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Fast-forward one week and I had my spare workshop day to do some building.  I decided to shelve my Clod rebuild for a while so I can focus on this one.

Here's the new L-section against the standard Tamiya item.

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Firmly clamping the stock chassis against the new section ensures the first two holes are drilled in the right place.

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Then screwing the brackets together through those holes ensures the rest of the holes are drilled in the right place

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So that we end up with a new, neatly-drilled chassis member

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The rear deck and the turntable have two holes that neatly line up, allowing them to be locked in place together with screws.  Not easy to see in these photos as I used neater stainless cap screws (ultimately all visible screws will be replaced with these).

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Mocked up trailer is now very long (it will need shortening)

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So, next problem - the kingpin.  Here I had to grab my HH container trailer to check the dimensions.  The HH trailer uses 40x20 L section, not 30x20, which means the chassis rails are 10mm higher.  The chassis rails have a rise towards the kingpin, which sits 10mm from the top of the chassis rails.  In theory that means the top of the chassis rail should be exactly level with the top of the fifth wheel.

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In practice, my chassis rail was a little bit too low.  I expect this is because of differences in the suspension on the pole trailer (given that it never had to match the fifth wheel).  A 3mm plate was enough to space it up.  In these photos I have shortened the chassis rails.

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So the solution is to use some alu plates to make a kingpin bracket.  I knocked this up in Fusion 360.  Unfortunately I don't have any machines to cut my plates, so it's back to the old method of electric jigsaw and hand-powered file.

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Brackets cut and test-fitted

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trailer bed is level

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and plate fits flat against the fifth wheel

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This is a mockup of how the finished article may look.

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Obviously in current form the trailer isn't usable - the alu plates are rigid enough to support the weight of the poles and would probably tug the load around without any real problems but there's some flex in the plate and eventually it will get a knock from something and fail.  A rig trailer should be solid enough to take some abuse (some rigs are carrying huge loads) so I'll need to beef up the bracket with some more L section.  I don't have anything in stock that is suitable so (yet) another order has been placed for more alu.  I think I am single-handedly keeping metal suppliers in business during lockdown :o 

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Now what the heck ya doin' ?

just can't get enough, oh but i like it............................

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On 4/27/2020 at 2:25 AM, Mad Ax said:

In practice, my chassis rail was a little bit too low.  I expect this is because of differences in the suspension on the pole trailer (given that it never had to match the fifth wheel).  A 3mm plate was enough to space it up.  In these photos I have shortened the chassis rails.

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i worked for Christy Machine Works for a very short time in San Francisco helping them transition to move to Sacramento, there was a Giant arched bronze straight edge level that was ornate to the hilt and it was sold and hauled away it was huge and a tractor trailer had to be used to haul it away, this picture reminds me of that day when i loaded it up with a fork lift.

the neat thing about working there for about a month i was able to keep a collection of various skeleton and some very ornate keys that the supervisor said i could have.

i have tried to google a picture of it, but have not even came up with anything that even resembles it. back then there was no cell phones, and i'm not a camera carrier.

soon as i saw your pic here, i wish i had. it looked like a museum piece. 

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I was planning to spend tonight catching up on some music and playing video games, but my first and last ever Lenovo gaming laptop decided to fry its motherboard for the 4th time yesterday morning, and the local repair shop who replaced some capacitors on the mobo last time it stopped working are not open during lockdown.  So there'll be no gaming or music until my new Dell G7 arrives in however long that takes (could be 20 days :o ) 

However, some good news, my new angle section arrived this week so I can crack on with the trailer.  The bad news is that I seem to have ordered the wrong size, but no matter, it fits well enough.

First off I needed to drill the missing holes in the kingpin plate.  I had previously printed and cut my CAD template so I glued it to the plate with generic white glue stick.  Other brands are available.

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Holes drilled as accurately as I can manage

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Then, cut the angle section to length, drill the holes, file the edges and attach

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Stock kingpin fitted for now.  Later I'll use a Servonaut kingpin with a housing for the Beier IR receiver.

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Fits perfectly on the Globe Liner 5th wheel

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Apologies for out-of-focus pic, this is the only one I took and didn't notice it wasn't in focus

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Next, mounting the pole cradle on top of the kingpin.  Stock kingpin hole helps to line it up properly.  My plan was to make as few cuts as possible into the original pole trailer in case I want to sell it on later, but here there was no choice but to make some new holes.

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I needed to file away some of the plastic from the back of the pole caddy parts, but this isn't visible when assembled.

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My final job was to replace all the ugly black JIS screws with stainless button heads from Westfield Fasteners.

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And the final rig, complete with plastic pole load

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Slight issue with the angle covering the edge of the fifth wheel, this causes the trailer to bind.  It seemed OK when I tested it on the bench but on a quick drive around the yard it didn't turn, so I will need to address that on Sunday.

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Posing shot before test-run.  Better shots to follow once the Beier system is plumbed in and configured, although that will probably mean setting the Sound Teacher app up on my old laptop...  Lame.

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More updates - I spent a fair bit of Saturday on the trailer conversion, much of it on time-consuming jobs like soldering, but I made good progress and only stopped because I was fed up with cutting and soldering wires.  Just got one more wire to do (I switched off the soldering iron and packed half the stuff away before I realised one wire was too short) which I will try to get done tonight, then the whole cabundle can be thrown back together for a quick test-drive.

Anyway, here's the progress so far:

I hacksawed, filed and sanded down the edges near the kingpin so the trailer would turn over the 5th wheel:

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My Servonaut kingpin arrived during the week.  My plans of not destroying the original pole trailer too much might have to go out the window, because the IR receiver will probably extend up into the base of the cradle.  So it will have to be opened up to allow it to fit.  I'm not planning on making a whole new cradle assembly.

Anyway, here's the new kingpin next to the old.  It needs a 4mm hole, not a 3mm hole.

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This is the IR receiver that mounts over the top.  This will be inside the stock cradle.

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I had to get at the Beier unit inside the rig to add the IR transmitter.  It's a bit of a mess in there as it was thrown in quickly for a weekend meet, back in the Before Times, when we used to drive our lorries in the company of other human beings.

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Since I won't be going anywhere for a while, I figured I'd do a tidier job on the pole trailer from the start.  I had to remove a few screws to get the IR receiver unit fitted but it sits very nicely between the frame rails.

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And that is the last of my photos.  I had intended to get some of the finished wiring on the rear light unit, but I didn't get around to finishing it.  Amazingly I started this job just after lunch (after finishing my TXT project and doing some more work on my F150 scaler, see threads in the 4x4 subforum) but still wasn't properly done by teatime.  But I've got a bit of spare time tonight so I'm hoping to get the wiring finished, take some photos and get it all back together.

I might even take a running video if I can get a battery rigged up.

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Took those extra photos tonight.  Here is the rear of the chassis - I used a half-round file to take out a recess for the wiring to pass through.

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And here is the rat's nest that is the light bar.  Having to wire up my own lights would be nicer if I was any good at soldering.  Or, indeed, correctly cutting things to the right length.  Feet not to scale.

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This rubbish photo shows what it looks like when connected to the IR module.  Note that the IR module has quick-release cable clamps, which are nice for prototyping and quick wiring and saves the hassle of having to buy a pre-wired connector block on a ribbon cable, but it does make the finished article look a bit messy.  Oddly the truck-mounted module has multi-pin connectors and comes with a pre-wired ribbon cable, but it is a thoroughly horrible ribbon cable that is seriously awkward to separate the wires from.  More of that on the Globe Liner rebuild thread that will come sometime later, whenever I get around to finishing it off.

Photo is rubbish because I had the roller door down and the artificial lighting is a bit poor unless I turn on the halogens, which have a tendency to give me sunburn on the back of my head.

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Final pic of the night - closeup up the rat's nest wiring.  At this point I put the camera away as I was planning on going out for a cycle ride, but before I set off I put a couple of zipties and some spiral wrap around everything, just to neaten it up a bit.  Action vid sometime later, when I next have the time and the inclination to get into the workshop.

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Got a little bit more done last night.

First, here's a pic of the wiring with the zipties and spiral wrap in place:

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Next, I had to abandon all hope of leaving the stock trailer parts largely unmolested, because I had to drill the kingpin hole out to over 10mm to clear the IR sensor bracket.  Actually I could have just made it 4mm and screwed the Servonaut kingpin through it, but the Servonaut kingpin has a woefully short thread and it's already having to go through 3mm of plate aluminium, so there was no hope of getting across the 2mm air gap and through the cradle plate also.

My drill press chuck only goes to 7mm, so I had to take it to 10mm with the cordless drill then file out a square-ish shape with a round file.

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Then I needed some holes for the sensor wire to pass through.  The neatest way would be to go down beneath the cradle, but the gap between cradle and the top of the kingpin plate is only 2mm, which would put too much kink on the wire.  Going down another layer would interfere with the 5th wheel.

So, safest option - out the back of the cradle then down through the chassis.

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Fitted and secured with hot glue.  The Servonaut bracket is only made from soft metal and after bending it a couple of times while test-fitting it is already feeling like it will snap.  Not overly impressed if I'm honest, sheet steel might have been a better material choice?  Anyway, the hot glue should stop it from moving around.

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Next I had to make up a servo cable extension to connect the sensor to the module.  Fortunately I bought a 10 metre reel of servo cable, some crimpy ends and the proper crimping tool about a year ago when I started messing around with Arduinos.

More use of hot glue to secure the cable.

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Top side looks neat, cable won't really be visible beneath the poles

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underside is tidy enough for my liking

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cable completely not visible from the side, unless you get right under it.  I doubt anyone will be below the level of the chassis on a layout.

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So after that I hooked the trailer up to the lorry.  Well, I positioned the trailer over the back of the lorry and taped the IR LED to the bottom of the kingpin.  All trailer lights work well enough for me.  They don't seem to be as bright as the lorry lights - then again the lorry is running on 2S LiPo and the trailer on a 6 cell NiMH, so maybe the voltage is lower in the trailer.  Maybe I should have used lower value resistors, or maybe my NiMH needs a top-up, as it hasn't been used in months, although I usually store my NiMHs at full capacity, unless I've got home late from a meet and they've all gone in the bag half-discharged.

Next plan - try to find some support legs.  I read an article some time ago on converting standard legs to motorised, but the only standard legs I have are attached to my HH container trailer (converted to flatbed).  I'm not actively using the HH trailer but at the same time it's too complete to cannibalise.  I also have a replacement laptop now so I can start doing CAD again, so maybe I'll 3D print some legs with mounts for micro servos or tiny motors.  Actually I'm pretty sure I could make some legs with some sliding stanchions using alu bar stock, threaded rod and a good quality tap, all of which I have here.  OK, looks like I'll spend today's skive-time* designing a leg...

*My current job involves about 5 minutes of coding followed by 10 minutes of waiting for apps to build and pass testing, during which I swivel to my other desk and work on something else...

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