MST CFX-W J45C

[Mad Ax 9329]

This is going to be a slow-burn thread over winter as I put my J45C together.  Every Saturday I'm on toddler duty, and we like to go out for a walk in the morning (weather allowing) or make some cakes or cookies or do some creative stuff, and in the afternoon we have a cuddle and a film.  And once the film is over she almost always want to move on to some mind-numbing Netflix series, so that's when I leave her to it and break open a kit box.

To be honest I've been meaning to start this little project for weeks but we've been having so much fun we haven't wanted to stop, so it took an unexpected afternoon off work with a temperature and fatigue (covid results came back negative ) for me to get started on this one.  As a special treat, we have My Littly Pony playing in the background, which is way more tongue-in-cheek than I expected is secretly becoming one of my favourite series to binge (it's not quite as good as Duggee).

Anyhoo, on to the project.  My long-term plan for this one is for it to be mostly stock, or at least, fitted with off-the-shelf hop-ups.  I've got too many custom rigs and, although they're fun, there's always something else to go wrong.  These are supposed to be great out of the box, so there's no need to spend hours in the workshop custom-hacking new parts.  However it will be fitted with my own LED setup (using an Arduino, when I get around to finishing the code) and also have front and rear winches using sail servos.

So, here's how it all started:

MST kits are nicely laid out, with the parts bags divided into steps.  The instructions aren't quite as easy to follow as Tamiya (one step can include several different parts and I sometimes find I miss one, or neglect to install a bearing) but assembly is straightfoward and the parts are well made.

My helper had collapsed with excitement at this point and wasn't much help

 

[Mad Ax 9329]

I managed to get a bunch of parts laid out before she woke up and wanted a cuddle

fortunately she was helpful and took photos

I have about 20 shots of the TV, which I can't post here because My Little Pony is probably protected by copyright

However she was helpful in sorting out my screwdrivers

[Mad Ax 9329]

Actually that's not true.  She was stealing them, along with my tyres.

Literally 2 minutes after this shot was taken, she was wearing the tyres on her wrists

However that was OK because it kept her occupied, and I was able to get this far

[Mad Ax 9329]

And that's about as far as I've got.  Saturday was too busy for any building, so we'll see what next Saturday brings.  I have already painted the body (photos to follow) but I need to add some flat clear to the outside.  Tomorrow is promising to be dry, so if I can clean and mast the body tonight I will get it sprayed during tomorrow's lunchbreak.  There is one slight advantage to all this homeworking.

(The downside is that my wife is usually home and wants feeding, but tomorrow she is making the most of her last day of freedom and going to find an isolated spot on the beach while the sunshine lasts, so I'll have some time to hit the body with some flat clear if I can get enough heat out of the halogens).

[ACCEL 2014]

who plays the Piano? 

i did when i was younger.

The MST was the  Correct Choice

Beach, sunset, i haven't done that in a hundred years.

 

[Badcrumble 4204]

Stick, stick, stick, stick, sticky, sticky, stick stick.

[Mad Ax 9329]

1 hour ago, ACCEL said:

who plays the Piano? 

The piano belonged to my gran, it was a staple of my childhood going over to her place and hammering out choons on it all night long.  I spent a while learning piano although not to any graded level, I can sort of get a recognisable tune out of it but I'm not very good, my fingers are too short and stubby can I can barely stretch an octave.  Still, it's nice to be able to play out some melodies that I can use in my electro compositions.

 

[Nicadraus 6201]

Nice rig! It's good that MST included metal suspension links and steering links for this kit. The standard CFX comes with plastic and does a lot of flexing. I'm sure you already know that the stock MST plastic drive shafts are prone to breaking/twist snapping (same problem with the Tamiya CC-02). So upgrading them would be ideal. I never thought I'd get hooked with my CFX. I enjoyed the build and fitting some custom parts too.

Anyway, enjoy the build and keep it posted. Lovely daughter you have.

[Mad Ax 9329]

Been a while since I updated this thread, but I managed to finish the chassis a few weeks back, on the 15th.  My daughter was busy doing her favourite thing, watching TV while surrounded by her own mess:

meanwhile I was cutting out my painted body.  Paint on here is a mix of Tamiya black, Tamiya white and Tamiya racing green.  It wasn't really what I was aiming for (I wanted more of a dark grey, and only added the green because it seemed a bit lifeless, like a home appliance) and it took my a while to fall in love with the finished thing - it lacked vibrancy, was washed out and generally a bit pants.  But then I threw some matt finish lacquer on the outside and suddenly it all came to life.

Then I cracked on and finished the chassis.  The only clear space I could find to photograph it was in the old utility room, my daughter having filled the rest of the house with the fallout of her own excess.

[Mad Ax 9329]

Fast-forward to 29th November and I had the kit tyres mounted up SSD wheels, and the body installed and decalled.  Taken under the white lights of the workshop, the body has lots its deep army green look and gone back to looking thin and washed out, like a cheap plastic toy.  There again, it will usually be seen crawling through the woods, far away from artificial striplights, so it's probably fine.

I had previously installed the body posts on the front (as per the book) but I was using magnetic mounts and they interfere with the light buckets.  I want to use LEDs on this rig, so I figured moving the magnets to the shock hoops would be better.

Using kit screws and dismantling part of the magnetic mount enabled me to get a tidy installation.  I added some hot glue after fitting the body magnets to lock these in place, I don't like how they flop around so much.

To fit the magnets on the body, I placed them on top of the chassis mounts, covered them with hot glue, then closed the lid.  Clearance was such that the hot glue took up the remaining space.  Wait for it to dry, then I lifted the lid and added more glue around the magnets to help keep them in place.  They fell off twice during fitting and fell off twice from their previous position also - those magnets just don't like being glued.  Nor, in fairness, did they like being installed with sticky foam, in their previous installation on my drifter.  Which makes them largely useless.  Hopefully my extra glue will last a season...

[Mad Ax 9329]

Next plan was to start working on my servo winch project.  I'd bought some sail winches as they were cheap, high torque, metal geared and continuous rotation.  However I didn't exactly understand how a sail winch works - they actually aren't continuous rotation at all.  They will do 4 complete rotations in either direction, and then recentre, just like a regular servo.  Natch.  That's not what I wanted at all.

So, first thing was to remove the potentiometer and install a voltage divider in its place so the servo always things it's centred.

I opened up the servo and pulled out the pot (there was a screw holding it in place).

Using a multimeter, I measured the resistance as around 2.5KOhms in the centre position, so I figured it would be best to use similar resistor values here.  These are 2.7KOhm resistors.

And hey-presto - it completely doesn't work.  When centred, the servo winds continuously in one direction.  I can find a place where it doesn't by moving the stick, but it's too far away from centre to be trimmed out.  To be honest I have absolutely no idea why this is the case, in theory it should work perfectly.  Resistor values measure OK when measured at the PCB (although the coating makes it hard to get a consistent reading).  Ultimately this rendered my plan of doing this on-the-cheap invalid - there's not really a way around this if the servo doesn't think it's at the centre position.

There are alternatives.  The easiest one is to take out the PCB entirely and hook up to an ESC.  The problem here is that I want immediate response in both directions - most cheap car ESCs have a brake function, and if I can't turn this off then I can't use it on a winch.  A shame, as I have a bunch of old ESCs lying around doing absolutely nothing.  The second problem is that, to prevent the winch from unwinding when towing, it needs a 100% drag brake.  Cheap ESCs don't have this.

The HobbyWing crawler ESC does have all the features I need, but it isn't cheap, and it's massive overkill for what I want.  I've tried to look up some wiring diagrams for making a winch controller but can't find anything suitable.  I have been intending to rebuild some Arduino software to work on this rig - I can have switchable lighting, adjustable steering and throttle ramps and winch control using a modification of my Arduino MFU, but the Arduino alone isn't sufficient to control the servo motor - it would need external drivers, and I can't find details on how to make a drag brake.  By the time I'm done researching, buying parts and experimenting, I'll probably be out of pocket by more than a cheap winch controller.

So - servo winches put to one side for now, I'll have to decide whether to buy some cheap winch controllers or just spend the extra and buy some ready-made winches.  I was hoping to save money on this project, not spend it :p 

[Mad Ax 9329]

After this I figured it was time to start wiring up for use.  If I can't have winches just yet, at least I can go for a test crawl on my 1:10 scale mountain.

Motor wires soldered, ESC and radio added, servo and motor wires tidied

My next plan was to add some arch liners.  I don't like seeing air under my rigs, but I didn't want to spend money on a proper arch liner kit or fabricate something out of plasticard that would get in the way later.  So I decided to use a bit of rubber matting that I acquired from the scraps bin of a local factory years ago.

I test-applied some UHU glue to the bottom of the step, which has been externally painted black, to see if it would affect the paint.  After a few minutes I got no paint coming away and the glue was nicely set, so I figured the paint was impervious to UHU.

So I cut off a scrap of rubber and stuck it in place.

Unfortunately all the moving around to get it in position did disturb the paint, so I've got some marks on the outside.  The obvious mark is the black line where the edge of the matting has cut through entirely, less obvious is the general lightening of the paint where the glue has stuck.

[Mad Ax 9329]

I tried hard not to be too upset about this - no doubt this truck will see a lot of action over the next few years and get a lot more scratches than that, I was never entirely happy with the paint anyway, I guess I'm just annoyed that I went to the effort of checking if the paint would be affected and discovered I hadn't checked well enough.

Anyway - on to the arch liners.

I cut around some of the protruding bits under the car to get it to sit flat.  Flash makes it look harsh and obvious but to the naked eye it just looks like an arch liner.

I fitted the other side with hot glue, which I should have used in the first place.  It feels secure enough.  I had to add a little strip to tie both sides together as the rubber has a curl in it from where it has been stored for many years.

Finished product installed

[Mad Ax 9329]

After this I went out for a test-run on my scale mountain.  I only really had a brief run around the garden, so it's hard to make any positive comments just yet, but I did notice two negative things

1) full lock is pretty tight - but is coupled with a jerking from the chassis, as if the CVDs don't like it.  I've seen pics online of people modding the drag link for more lock, but they might be using different CVDs.  No point adding lock if the CVDs won't allow it.  That said, it could just be the tyres scrubbing because there's no diff action.  I'll give it another test on the workbench when I have time.

2) stock tyres are awful.  OK, maybe I'm being unfair, they might be good on mud, roots, or even smooth wet rock, but on my scale mountain I couldn't even make the start of the climb.  My SCX10 on Prolines will do this climb - it's a challenge, but it will do it - but the CFX just didn't want to know.  After 10 minutes of trying I eventually gave up.  The rock is actually mostly old concrete that has been broken up and re-set in a heap.  It's pretty sharp and gives good traction for anything with side-bite, but the kit tyres are quite rounded.

So - again my plan of a cheap end to this build has been thwarted, as it looks like I'll need some better tyres for the sort of terrain I do (at least at home).  The first runs are likely to be in the local woods, so I'll have to see how they go there before splashing out.  Maybe they'll be fine.

More to follow whenever I get around to doing something else.

[Mad Ax 9329]

Updates!

After fitting the lift mechanism to my Grand Hauler tipper and setting it to rest while I considered the next steps, I figured it was time to re-investigate the winch system on the CFX-W.  Earlier in the week I'd bit the bullet and ordered some winch controllers from Banggood - they appear similar to the controllers that came with my 3Racing winches, which work well enough, and are cheap.  Way cheaper than using a crawler ESC and way easier than trying to make something myself.

So - I dug out my modified winch servo and looked at where to put it.  I had originally intended to build a simple and sturdy servo mount on one of the electrics trays under the cab and route the cable through an antenna tube, but I figured that was going to give an uneven load and potentially all sorts of stability problems if I use the winch on the trails.  I want this to be a really practical runner, so I figured a front-mount installation would be better.

Note: the stock bumper is actually big enough to install a scale winch, but as it incorporates a fairlead, and scale winches can be either expensive or weak, I figured an internally-mounted winch would be better here.

There is space for a full-size servo up front, mounted in front of the motor, but it's quite tight.  To line up with the fairlead the winch needs to sit upside down between the frame rails.  The stock bumper incorporates body post mounts and these need to come out to allow space for the servo.

This is the stock bumper.  It's a tough, rigid plastic.  Difficult to hacksaw but easy enough to Dremel.

This is the stock bumper with part of the body mounts removed.

[Mad Ax 9329]

With that done, I needed to make some servo mounts.  I considered using Delrin but it's no easier to work with than aluminium, and alu takes a thread better.  Plus I already had some alu bar in 10mm square section - exactly the right size.

It took 20 minutes to cut off two short lengths and tap some M3 threads.  I had to widen a body post locating pin hole in the chassis rails to 3mm, and also drilled out the rearward securing screw holes in the bumper to 3mm.  The screws pass through the bumper mounts and into the new servo mounts.

Now the servo can sit upside down on the new mounts.  Marking for screw holes:

[Mad Ax 9329]

Another 15 minutes with the drill press and the M3 tap, and I had the servo mounted.

[Mad Ax 9329]

Now, the keen-eyed among you may have noticed a problem.  The daft thing is, I spotted it before I started and then forgot about it when I was making my mounts.  It is thus:

The steering servo hits the winch servo on compression.  Gah.  It will be even worse with the stock winch drum installed.

So there are to parts to the solution.  The first is to remake the servo mounts a little longer, to shift the winch servo forward.  There is a few mm space left between the servo and the front of the body, so it can move forwards just enough.  It didn't take long to make the original mounts and they can be used as templates, so making new mounts should be the work of but a moment.

The second part is to replace the huge drum that came with the sail winch with a smaller drum designed for crawler servo applications.  I've ordered a couple from ebay for almost nothing - won't be here for a while but there's no rush.  They also come with some wire (which might not be perfect but better than what I have, which is absolutely nothing) and some hooks, which are actually quite expensive to buy on their own from the regular brand names.  So in theory I now have everything I need on the way to me.

I also took the plunge and ordered some Hyrax 120s.  I've been using Flat Iron XLs on the SCX10 for a couple of years and they've been brilliant, the Hyrax looks like an update to the basic design so I hope they'll be even better.  They look to have way more side-bite than the stock tyres, which is what I need to get over my scale mountain.

I still need to add some scale decals, wire up some LEDs and sort out my Arduino controller project so I can operate all the lights and two winches from a 6ch radio.  Arguably I can do that already from a 6ch radio, but I can add new features such as working brake lights, various levels of light operation, safety switch so the winches only operate when activated, and a switch to flip the throttle over to left stick so I can drive one-handed for taking photos.

[87lc2 2666]

Truck looks great, I really like the color (even if you aren't so fond of it).  The SSD wheels look fantastic, I have a set of the 1.55 beadlocks on my CFX and they are great.  You'll really like the Hyrax compared with the Flat Iron, I have been really impressed with them.

I've only built a couple MST kits but I really enjoy them, nicely laid out and nice quality.  I have yet to break a single part on my CFX after many hours on the trails. 

Also really nice to see your daughter.  I just had my first 4 months ago and it's been a huge life change to say the least.  My hobby time has been scarce since, but I wouldn't change it for the world.  I can't wait until she's older and we can do more things together.  With any luck she'll be into RC & 1:1 cars in at least some capacity.  I'd think she'd have to be being my daughter   

[Mad Ax 9329]

Thanks @87lc2, it is really growing on me - it's a sort of vintage army green, I keep thinking it would look great with some stencils on the bodywork but I'd have to airbrush it and run the risk of royally screwing it up.  Anyway, I doubt any army would run a trayback crawler on portals and 47" tyres, so this has got to be an army surplus truck that was sold off and converted for civvie crawling.

I actually like the colour right up until I see the boxart anthracite, which just looks awesome.  I love anthracite, and I almost painted it Tamiya gunmetal, but I already have a lot of gunmetal cars (including my original SCX10 body) and have an aversion to boxart, since I don't want to turn up on the trails with the same rig as someone else.

I love the wheels - for the money they're great.  They're stamped steel as opposed to billet alloy like the more expensive ones but they're honest and easy to assemble.

The chassis came together well although I find the instructions and the layout of parts slightly confusing compared to Tamiya.  Having 2-3 sealed packs of screws for a group of steps makes sense but sometimes there seems to be no logic to how they are bagged - unless I was opening them in the wrong order.  Plus having a single overview of parts for half a dozen steps on one page meant I had to keep flicking back a few pages to be sure I had the right size screw.  I like that Tamiya puts a scale diagram on the side of each step so I can always check the screw sizes without changing the page.  TBH if I was building "properly" on a big desk with all the parts neatly laid out then I wouldn't notice any of this, but I was trying to build perched on one end of the sofa on a little flimsy fold-up table with my parts and tools scattered around me on the floor.  Earlier this year I put a big camping table in the lounge so I could watch films with my daughter while I was building but it went in the back of my camper when the racing season started and still hasn't com out again :p 

I am having some issues with the drivetrain - I found the axles were binding quite badly when I tightened up the diff covers, I disassembled and reassembled a few times to be sure the bearings were seated and there was nothing on the gears that shouldn't be there, then I noticed it went away if I backed off the diff cover screws a little.  I think of myself as being mechanically sympathetic and generally gentle with my screw torque (machine screws into plastic don't need much torque) but maybe I'm too ham-fisted for this precision instrument.  Also I turned the wheels over at the weekend and got a clicking from the transmission somewhere, it's only had one careful run around the garden and one attempt to climb my mountain, so I need to work out what the problem is there.

Having a child sure changes your life, it's the biggest adventure you'll ever have and there will be lots of fun times to go with all the hard work.  They don't really do much in the first year but you can make the most of that - daddy/daughter days can involve taking her to places you want to go instead of where she wants to go  as long as she's with you she'll be learning and having fun and bonding.  I took my daughter to loads of country parks and animal parks in that first year and could walk around at my own pace while she was strapped to me.  Now she wants to go at her pace which is way more awkward

My daughter hasn't really got the hang of driving her Lunchbox yet but I bought her an FTX Outback Mini X (with the LC90 body, which IMO looks awesome and totally scale) which should be much easier to drive and we can play with it indoors on Christmas day.  Actually I wish I had the cash to buy one for myself so we could drive around inside together   She'll be 4 in February so just about the right age to start learning I think.  I'm secretly hopeful that she'll get right into it and join me at the vintage races when she's old enough but who knows, I might get dragged around to ballet performances or football matches instead :p 

 

[87lc2 2666]

Yea, I understand what you mean.  It would be nice if she takes to my interests, but I'll never force her into anything.  whatever makes her happy and productive is OK with me.

I would agree that Tamiya kits are laid out best by far, no argument there.  I find Axial kits to be well laid out also.  Now that I think about it I do remember the MST being a bit confusing in spots.  Surprised you're having issues with the transmission/axles.  I dont have this model MST, but the two I have are exceptionally smooth.  Every time I have them out I'm surprised all over again at how nice they are.  I've had that issue with tightenting axles together on other models (namely Axial) and it drives me nuts.  I'm the same as you, I typically use just enough torque to where it will stay put but not be overly tight or distort any parts.  When I get binding I hate having to keep the screws "looser" than I determine what should be the proper force.  

As far as the color, I personally really like it.  It will  look better with some scratches, they always do    This body & color would also really benefit from having the body lines accented, have you tried the Tamiya Panel Line Accent paint?  It's pretty cool and works really well on static models and ABS bodies.  I haven't tried it on lexan yet, but I dont see any reason it wouldnt work. 

[Mad Ax 9329]

I've got an MST RMX 2.0S and I found the build a real joy and the car has given me no trouble at all.   Admittedly a drift transmission is much simpler than a front-motor crawler but even so, it's very smooth and nicely made.  I guess there's either something loose or not assembled properly in my transmission.  It might even be something in the can, it sounds like it's coming from the front.

I haven't tried the accent paint but I might give it a try.  The body is mostly thick and solid (although a bit thin around the door steps and was very easy to trim), and the shut lines are deeply moulded, so accent paint should have enough space to take hold.  I didn't know about it until recently but it looks way better than the tape - I tried that once and I couldn't get it to sit straight, I don't have a very steady hand for that sort of thing.

[87lc2 2666]

Yea, I've never had luck with the tape either.  The accent paint is pretty impressive, i would give it a shot.  There are a lot of videos on YouTube of guys showing how it works, really brings models to life.

[Mad Ax 9329]

Sunday's weather was mild for the time of year, but it was raining heavily and forecast to continue for the rest of the day, so I decided to have another Workshop Day and get more done on the CFX-W.

I'd left my main workbench in disarray from the previous week, so my first task was to put away the tipper truck and clear a space to work in.

With that done, I could start work

Last week's attempt to make some winch servo mounts failed when the servo hit the axle under compression, so my first task this week was to re-make the mounting brackets a little longer.

there is now plenty of space between steering servo and winch servo

[Mad Ax 9329]

Next, I needed to fit my winch controllers.  I got these from Banggood with faster-than-expected delivery and a bargain price.  Let's hope they hold up.

They're a bit too big to fit inside the servo case, so I need to solder on some wires to the motor and run them externally.

After that I plugged in the winch controller and tested it - it seems to work perfectly.  Well, it operates the servo motor in either direction, and that's what I wanted.  In theory it should act as a brake also but I didn't have a horn on the servo to prove that point.

In theory this little controller is a very simple but of electrickery but I don't know exactly how it works and can't find a wiring diagram for it.  It would be nice if I could make my own small enough to fit in the servo case.

I reassembled the servo housing and put some hot glue around the wire to make it water resistant.  Every good crawler will get submerged from time to time.