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Mad Ax

Project Top Secret - Element Enduro Scale Builder's Kit

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So I had another idea about the transmission last night.  I was starting to think I'd have to pull the planetary transmission out of my long-stalled King Hauler drag truck project, which I didn't really want to do as I'm not sure how the gear ratios stack up between the Axial and the planetary, and I'm finding I spent longer and longer trying to work stuff like that out, which takes time away from actually building stuff.

Well, I mentioned about installing the transmission sideways (my original attempt to get it in had involved mounting it at an angle, but that didn't work so well).  Now I can't really get it in sideways on the RHS because the front prop and upper axle link are in the way.  I can flip the transfer case to move the front prop to the other side, and it seems I can move the upper axle link too without affecting the geometry.  Worst-case scenario is that I'd have to reverse the panhard rod, steering servo location and servo link, but all those parts are modular and reversible, with the slight exception of the panhard connection on the axle, which is moulded to only go on one side.  It'll work the other way, but will be very slightly out.  But I don't think I need to do that anyway.

So, hopefully, I've saved myself a fair bit of hassle getting the transmission installed.  Fingers crossed.  That means I can keep the stock servo mounts, and that means I can run a winch servo up-front, saving a whole lot of pennies on a winch and an aftermarket bumper to mount it on.

I also found some shorter, stiffer shocks to try in the rear, but on the highest available setting (without having to make all new hoops) the axle loses about 10mm of downward travel, and they're too stiff.  While it would make for a more scale rear-end and allow for a more realistic trayback, this is supposed to be a capable rock rig so I don't want to make it too stiff or low.  But it's still something to consider as I pull the back end apart again at the weekend.

As I'm planning to swap the SBK-1-style hoops onto the front, that will increase the ride height out front, so I need to do the same in the back.  Fortuitously, I drilled a slightly more upright rear shock position when I made my angled shock hoops, which will serve both to lift the rear end and to stiffen the stock shocks.  So maybe I can retain the stock shocks after all.  Alternatively, I could make some all-new front hoops and drop the front end down to match the shorter rear shock version...

There's a whole heap of options available to me here, the problem will be picking one and getting it installed and set up before I have to set off for the event in a month's time :o 

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I know you're all hanging up the big one - the update from Revival 2022 - but the week has not entirely gone to plan and I haven't had the time I need to sort through over a thousand photos, let alone wait for them all to upload to the net.  So instead you're getting the 6x6 update that should have gone out before I even set off for the Revival.

So, I started with this - the Big 6 project (which is actually its official title), with no transmission.


As I alluded to earlier, I was able to relocate the top link to the other side to clear space for the transmission.  In this arrangement, I'm connecting into the 1:1 drive on the transfer case, which will give me around 25% overdrive at the front axle.  I wasn't planning on doing it this way, but the general consensus is that 25% isn't too much and it's easier than flipping the transfer case around.


I got another offcut of 2mm aluminium plate and drilled it so it would attach on the standard holes in the chassis rails


aaand at this point I had to pack up and go in, as it was time to do...  er, something else.  I can't remember what now, it was pre-Revival, and as is normal for an RC camping weekend, most of what happened before is kind of a blur.

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I was up super-early on the morning of Saturday 3rd.  My daughter was staying away until Sunday afternoon, so I had a day and a half to get in the workshop and hack at this monster project until it worked.

I started my mounting the Axial transmission onto the new side-mount plate.


In this angle, we see that the output shaft from the transmission is near-as-dammit inline with the input shaft of the transfer case.  I don't have the time or skills to CAD all this up or otherwise measure to see that it will be spot on, so there's going to be some trial and error here.


I started tidying up my side plate, so get it to sit neater against the chassis


then I redrilled and notched the top rail mount plate / shock mount plate on the middle axle - you will see why in a moment (and you won't like it)



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My main concern - this being of the crawlery persuasion, heavy and with lots of 3S torque through a yet-to-be-purchased 5-slot crawler motor, is that my flimsy 2m mounting plate will basically wrap around itself as soon as the truck hits a tricky climb or sinks an axle into a hole.  So, I wanted to make a brace bar to stop the plate from twisting.

It was around this point when I started to have serious doubts about this installation.  Solutions should be elegant.  The old engineers adage says "if it looks right, it probably is" - therefore the reverse must also true.  If it doesn't look right, it's probably wrong.  A solution that doesn't look elegant may work fine, but something about this just looks wrong.


And here we are, with everything bolted in place.  Sort of.


At this point, we hit a snag.  I couldn't get the camera in the chassis to take a picture, but the output shaft of the transmission was no longer in line with the input shaft in the transfer case.  All the moving of the pieces as I cut and fiddled and spaced them around had pulled it all out of line.  Here I could have gone crazy and cut more spacers, or re-drilled the transmission mounting holes, but I was feeling deeply uncomfortable about this solution and decided to abandon it for a while.

Also at the same time, my neighbours went off out for a ride on their Triumph Bonneville.  My wife, standing in the sunshine watching them go, said "we don't have any childcare duties today, why don't we go for a bike ride?"

And so we did.  That was pretty much the moment when I realised this rig was unlikely to be ready before the Scaler Nationals at the beginning of October.  We're almost two weeks from that fateful moment, and it's still no closer to being ready, so at this point, unless I start pulling sickies from work, it really isn't going to be ready.

Which is a shame.  I may even paint the body and finish the trayback so I can take it along for display purposes only, but it's not going to turn a wheel on the track.

The bike ride took the rest of the day, and the next morning I had to do some work on my Revival racers before the crazy week-long packing process took place.

I managed to get a tiny bit of work done this lunchtime, so there'll be another update to follow when I've got the pics of the camera, but it's unlikely the rig will be ready.

But that's OK!  It gives me more time to focus on getting the other rigs ready for the big bad showdown.  Maybe - just maybe - I'll even see what's up with the Toyota trail truck and get that running, since it hasn't done a proper crawler event.  It's technically now a truescale rig, so it won't do much on the proper courses, but there's usually a little course specifically for truescale trucks, and it would be nice to see it run again after all the money I ploughed into it back in 2020.

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One of the major bonuses of working from home is, during term time and when my wife has a work contract at least, I can get an hour of wrenching in the workshop while the sun is shining and there's a lunchbreak to spend.

I need to give the CFX-W a proper going over and a bit of a scrub before the Scaler Nationals in 2 weeks - it's still got dirt on it from the SST quarry day back in April - but first I wanted to pull out the transmission to see if it would fit in the Enduro chassis rails.


The CFX-W transmission is a fairly neat package, and while a little top heavy, certainly looks right for a scale-correct front-motor build.  It fits very securely in the CFX-W chassis rails, but there's a very slight design philosophy difference between MST and Element.



First problem - the pre-drilled holes in the MST transmission mount don't line up with the Enduro chassis rail holes, so new holes would need to be drilled.

Second problem - the CFX-W chassis rails are taller than the Enduro chassis rails (i.e. the channel is wider), so the CFX-W transmission mount won't slip into the Enduro rails without modification.  This isn't a showstopper, but it means once I've started I've compromised the CFX-W part, and would want to replace it with new (the mount bracket is separate from the transmission housing and can be unbolted and replaced separately) if I ever put the CFX-W back to standard.  Since this is only an exploratory mod, I didn't start filing away the mount - it's just loosely held in place.


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This shows the UJ angle with the transmission mounted on the rearward of the available holes


This is a bit steep.  In fact just turning it over by hand, my dummy UJ threaded rod would unscrew instead of turning the opposite UJ.  So this won't work.

I tried moving the transmission forward, and although that makes it slightly better, there are issues with the mounting bracket fouling on the panhard rod mount.  Now, this alone needn't be a problem because the type-1 Enduro shock hoops have their own panhard rod mount (the type-2 is a separate adjustable metal mount bolted to the chassis rails) but also as the transmission moves foward, there's less space for a steering servo.  The CFX-w gets around this problem by using the older, slightly less scale solution of an axle-mounted servo, but that's not an option on the Enduro.

Now, there is an alternative option here, which is to install the transmission under the rails, by making some drop brackets.  This means I wouldn't have to cut the bracket to fit the rails, either.  This solution solves quite a few problems, but still doesn't leave much room for a steering servo.

Thumb not to scale.


The other big issue here is recommissioning the CFX-W after the transmission transplant.  The CFX-W has a neat transfer case mounted on the skid place, but the hole pattern is totally different to the Axial or Element transmissions (which are similar but not identical to each other).  Also the centre plate has some moulding pattern in the top to accept the CFX-W transfer case, but not any other transmission (except possibly the CMX?)  So there would be some work involved here.


Does this completely prevent the possibility of using a CFX transmission in the Element?  Well, no probably not, but it does make it somewhat more complicated, especially if I want to get the CFX-W running again in some way.

One option, as I mentioned in my Overthinking thread, is to buy the smaller CFX chassis, steal its transmission, and build it with the spare Axial transmission into a CMX.  But that's not an ideal solution, as the base plate will cause some added work, and it does mean having to justify a whole new chassis when I already have a lot of projects on and not that much spare cash.  It's a shame that MST don't sell modular parts - I can buy the parts to build a complete transmission, but I have to buy them all separately, and it's not cost effective.

Another option is to buy one of those cheap front-mount transmissions from Aliexpress, but they mostly seem to have their mounting brackets shaped to fit the curved front chassis rail like most SCX10 clones have, and I think that will make them awkward to modify or fit, and they'll probably have loads of slop (like the Aliexpress transfer box I'm using).

Finally, I could use the smaller, simpler planetary transmission used in some bigrig builds.  I have one (I think made by Lesu) in my long-stalled Drag King project.  I'm not sure how the gear ratios stack up, but it might not take long to pull it out of the Drag King and install it to find out.  I'll probably have a go at that when I have time, but the Drag King box is in an awkward place and I've not got a lot of time to get the Scaler Nationals rigs ready (especially as I now have to rebuild the CFX-W's front end, too!)

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Another real quick update on this project, when I had a few spare minutes after working on the Scaler Nats rigs (of which this was supposed to be, and probably would have been, if a) I hadn't got side-tracked making a tray back and 2) I hadn't had so much trouble with the transmission install).

Anyway, one thing I really wanted to try was a planetary-type transmission.  Fortunately I had one, although it was in the Drag King project, which was right at the bottom of a stack of boxes on a really difficult place to get at.

Here's the assembly installed in Drag King.


And here's a very rough installation using an existing hole in the chassis.



The prop isn't connected in this last photo, although it previously was connected, but it came off during a test run.  The point is though, it did actually work, all the wheels were turning nicely and nothing was binding.


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Good to see some progress on this after your recent issues. I'm not sure such as thing as a 'quick project' exists!

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