Fifty-Fifty: WT-01 Pro-mod with F250 body

[Mad Ax 9313]

Updates!!  Sitting here waiting for a mate to pick me up to take me out for drinks for my 40th, what better to do than catch up on some TC admin..?

So - paint went on at the weekend, surprisingly well given the weather, temps and the fact that I also had to look after my 3 year old because the wife was out.  Colours are PS-23 gunmetal and PS-19 camel yellow, with a little bit of Fastrax Spa Silver backed with Tamiya PS-12 silver.  Obligatory pre-decal shot:

[Mad Ax 9313]

Decals arrived.  I went with these:

https://mciracing.ca/products/blank-2-color-c2a668bd-cf21-4d17-8c80-60a57316952b

and these:

https://mciracing.ca/products/blank-2-color-7042a45f-50a6-40f2-8d46-b71ad03c7e79

printed in Sunflower Yellow, and of course my own Fifty Fifty designs printed in black on clear, by a friend of mine.  He charged £11 posted and included multiple print runs so I've got a load of spares.  Just as well as I changed my plans for the bonnet and was glad I had some bigger decals to go there (the original design only had big logos on the sides and a small logo on the front).

I also used some generic crawler / monster truck sponsor stickers that I had lying around, some from MCI Designs and some from somewhere else.

These are a handful of pics - there are loads more on the link:

[Mad Ax 9313]

[Mad Ax 9313]

http://tcphotos.net/album/BUXR

 

First run report to come later - right now I'm about to pack up and go out.

In other news I'm slightly sure the body is just a little bit too far forwards.  I might re-print my body mount brackets to relocate it back about 5mm...

[Grumpy pants 4485]

Happy birthday @Mad Ax it’s a quite a milestone 👍

Hope you had a good night with your buddies. 

[Mad Ax 9313]

I had a fab night, I'm not having such a great morning.

I'd love to say it's because I ate and drank too much, but I literally only had 2 pints and a single brandy 

Never mind, a steady day and some more TC admin beckons  - as well as loading up the van for this weekend's Tamiya Junkies meet

[Mad Ax 9313]

I have just realised that I never posted any updates to this build.  I guess the excitement of the Tamiya Junkies meet back in Feb put it all out of my mind for a while.

So - first impressions were that the rig is way too heavy.  My 3mm alu chassis plates and shock towers are fairly chunky and it's a heavy rig already with two motors and transmissions installed.  Even with those alu shocks, it's still too soft to drive properly.  I tried jumping it in my garden a month ago and the rear transmission belly-slams into the ramp before it even takes off.

I could tighten up the springs but the bottom arms are already showing signs of twisting from uneven torque from the shocks.  This is partly because the shocks are spaced out at the bottom (to clear the 3mm thicker towers and because shocks are wider than stock) but also because the rig is so heavy.  In short - I need to lighten it up.

Solutions - 1) drill out the chassis plate to make it lighter or 2) have carbon plates made.  1) I can do at home for free, but I'm not an engineer and don't have huge experience with alu, and I'm slightly nervous of taking too much out and ruining it.  Also I guess I'm worried about not making a tidy symmetrical job on a build that has so far been fairly clean.

Another issue is the body mounts printed in resin.  I printed a new set that relocated the body slightly, but broke one during a rollover on my garden and haven't got around to printing another yet.  I need to investigate a tougher resin, but last time I looked (pre-Covid19) it was hard to consistently find a reasonably-priced product in the UK.  I'm guessing in the current climate it could be hard to find anything...

I can add a bit more meat to my design.  I haven't cleaned my printer since a failed build got stuck to the vat back in February so I might have a bit of fun later trying to get it off without ruining the film.  I'll probably eat through my diminishing supply of rubber gloves to do that...

@ThunderDragonCy - we briefly spoke about making a drawing for carbon plates.  I tried to PM you but you can't accept PMs - let me know if this is still something you're happy to help with  

[ThunderDragonCy 7878]

@Mad Ax Ooops. Inbox was full. Definitely keen to help. PM me now and it should work. I had a clear out.

[geniusanthony 361]

3 hours ago, Mad Ax said:

mounts printed in resin

I've gotten fairly good with nylon on an fdm machine.

If the geometry is conducive I could print you off a set in taulman 910.

I can't break break my custom body mounts even when Watanabe Clod rolls over, same of the Blackfoot cr01, it's tough stuff. 

 

[Mad Ax 9313]

UPDATES!

So - this rig has been in pieces for most of the year, as I sent my chassis plates to @ThunderDragonCy who very kindly did some technical drawings from them so I can have my chassis plates manufactured in carbon.  I've been so snowed under with other things that I didn't bother to put it back together until yesterday evening.

The first problem I wanted to address (before spending silly money on carbon chassis plates) was the twisting of the lower arms.  This was happening partly because the big bore shocks were mounted forward of the shock tower extensions, and were so far away I had to install a long screw and spacer to attach the shock eye to the bottom arm.  The soft plastic was twisting under preload and upsetting all the good work I did to add some caster angle to the front.

Here's the front end, with the tower removed:

And here is the trial solution, using spacers in the tower mount to move it forward.

Clearance is tight but practical

[Mad Ax 9313]

This is a much more acceptable installation

And with the chassis plates reinstalled

 

There are some drawbacks to this solution.  The standard shock mounts interfere with the shock, so I can only install on 1 of the upper mount holes or 2 of the lower ones, so there is less tunability.  Also something feels a little wrong about using spacers - a bit impact could bend the screws or rip them out of the plastic.

With that in mind, I might modify the chassis plate design to install the shock tower directly to it.  I could cut the stock top mounts off the gearbox housing, and have a neater installation.

That wasn't a project for a Tuesday night, so it's currently sitting on the workbench waiting for Sunday, which is forecast to be wet and windy - perfect weather for camping out in the workshop with the log fire blazing away.  Watch this space!

[Mad Ax 9313]

Got a little bit more done yesterday afternoon.  Actually I didn't expect to do as much as this, but even though it was clock change day I didn't feel tired or hungry, so I just kept going.

I needed to remove the stock shock mounting lugs from the gearboxes and mount the new shock towers onto the inner part of the gearbox.  To start with, I drilled my two new mounting holes into my shock towers (again, I did this with both towers bolted together so they come out identical).

I was then able to bolt the plate up against the stock mounting holes, and use the plate as a template to drill my new holes.

With that done, knowing the towers would be in the right place with my newly-drilled holes, I could chop off the stock shock mounts

There are some problems here.  1) the gearbox casing is hollow here, so it will let in dirt.  I'll need to seal this later.  2)  The gears will now be covered in plastic swarf from my drilling, so I will have to open up the gear cases and clean everything.  3) I made a mistake and drilled from the (nominal) front instead of the back, and I had to use a hand drill, so there's no guarantee that my holes are straight.  The plates will mount behind the stock towers, instead of in front, so now I will have to bolt my tower up to some holes which may not be exactly right.  The only solution here is to get a new gear case.  (Later on I would do some measurements to confirm that the holes were actually more or less OK, at least as accurately as I was able to measure, so I don't think this will be an issue for me just yet).

Next thing was to chop off the bottom half of the tower and file it to clear the moulding of the gear case.

Here I realised I'd made another little mistake - I could have left the lower mounting lugs in place on the towers, where they attach to the upper arm pivots.  This would have a) added more rigidity to the tower and 2) moved the lower arms back a little to help clear the shock springs.  Well, live and learn, I suppose - I was trying to work fast as I didn't have a lot of day left.  There's definitely a place for patience when making custom parts!

[Mad Ax 9313]

Anyway, no worries - progress is still progress.  Shock tower fitted and mounted in one place:

This fitment won't be very strong.  For more rigidity it will be tied into the chassis plates here.  I had to trim a little section off the rear of the chassis plate to clear the tower

I cut some 90 degree brackets from alu angle and bolted them to the towers:

Then I was able to drill the chassis plates and add a single mounting bolt

[Mad Ax 9313]

Chassis with rear gearbox and tower attached

I then turned my attention to the front.  It was mostly a copy of the rear, but with more chopping required as the front gearbox is angled backwards.

Final assembly:

 

[Mad Ax 9313]

OK - so what's next for this project?

Well - I need to strip it down, clean the gearboxes and block off those holes.  I also need to rebuild the shocks, as during a drop test the rear right wasn't moving properly and seems like it's sticking.  It sounds like it has air in it, despite being rebuilt when I put this project together earlier this year and having very little use since then.

Another more serious issue is that of body mounts.  My home-printed mounts keep breaking - that's not a big problem as I can have a friend make them in PETG.  But now the shock towers are encroaching on the mount area, so the mounts I've designed won't fit.  I'll have to make some new designs.  It's possible I'll have to relocate the mounts slightly which could mean re-drilling the holes in the body - that will be a shame as I put a lot of time and money into that body and up to now it's been looking really good.  I could possibly paint some sticky sheet to cover the old body holes, but it's not ideal.

Also the suspension needs to be set up all over again.  I used inner mounting holes for the shocks just to prove they would fit, but they are way too soft.  Even without any electrics or body, it bottoms out from a 12 inch drop.  I need to reposition the top holes and add some preload to the springs.  The twist in the bottom arms should be reduced using to better positioning, but too much preload is still a bad thing - so a further diet may be in order.  I got some new hole cutters this weekend so I can swiss cheese the plates to reduce weight.

More updates next time I get a few hours in the workshop  

[Mad Ax 9313]

Sunday dawned dry and bright, and I had thought I might take the last opportunity for a motorcycle ride to the south coast for some fish and chips, especially as I've now got at least 4 more Sundays in the workshop with no racing to take me away from it.  However the weather on the south coast was 45mph winds, which might not seem that much to those of you from hurricane climates but it doesn't make for a very enjoyable ride, nor if I'm honest, does it make for a relaxing stroll along the Cobb.  And fish and chips, the quintessential English delicacy, is not enjoyable either when its traditional paper wrapping caught by a gust (or a gull) and strewn across the pebbles.

So I got straight to the workbench and the WT01 which had been gathering dust and condensation since last week.

Next point of order was the body mounts.  The photo below shows my (broken) resin mounts and a length of 20x30mm alu angle which was left over from my pole trailer build.

That much alu was a bit unwieldy, so I started by chopping the angle down to a more wieldy sort of size, then drilled some holes and screwed it to the chassis plate.  I needed a bit of extra height to clear the shock towers (now that the relocated towers are close to where the posts are), so I used a length of 10mm square section to space the angle from the top of the plate.

[Mad Ax 9313]

With the two locating holes drilled, I was able to drill more holes along the plates.  The plates are 3mm alu so unlikely to bend in a regular roll, but the angle is a lower-grade material and is about 1.8mm, so could possibly bend, and if it does, will probably crack and sheer.  With that in mind, I figured it best to add the screws at two levels, to prevent the angle from twisting in either direction.  Ideally there would be more overlap to spread the load further, but that's as long as my angles go.

Ignore the second set of holes at either end on the angle rail - I drilled those earlier by mistake.

Chassis plate reattached and angle adjusted so that is fits neatly over the shock towers.  There was actually a lot of work here because the front tower was very close to the mounting screw for the post, lots of trial fitment and filing to get to this stage.

[Mad Ax 9313]

It was at this point that I realised I'd made a critical error.  On my original chassis plate, there were two staggered holes at the front and rear (copied from the stock chassis plates) and I designed my original resin body mount brackets to use these holes.  The body posts were mounted equidistance between the two holes, so the same mount bracket could be used front and rear.  However I made a mistake when cutting the body holes, and had to re-make my plates with the post hole offset by around 10mm to re-align the body with the wheels.  This means the front and rear brackets were different (because the holes in the chassis are not level).  And therein lies my mistake.

I'd returned to my 3D design for my body mount brackets and calculated the amount I'd need to offset the body post hole from the existing hole in the chassis plate, but I'd neglected to check which bracket I was measuring, and in fact applied the measurements from the rear bracket to both ends.  That means the rear post was in the right place but the front post had gone in the wrong direction.  I'd extended it fowards when I should have gone back.  Which meant all that work I did cutting and filing my angle to fit over the towers wasn't needed after all.

Here's an updated photo with the post in the right place.  Front is to the left.

Also note here the holes in the plates, which I made for weight saving.  I'm no expert in material forces and I'm using only my own intuition to work out where I can put relief in the plates without affecting strength, but I saved a whopping 27g in total by doing this.  I probably added more weight by switching from small resin post brackets to long aluminium ones, but there you go.  In theory I could add more lightness by cutting out a huge centre section from the angle and adding a plate of 1mm ally across the top to make up for lost strength.  Maybe later.

And finally, the chassis reassembled

[Mad Ax 9313]

So, what next?  Well, we're not far from getting the truck mobile again.  The next trick is to open the gear cases and clean out the swarf, then seal them up with hot glue and reassemble.  I didn't really feel like doing that at 15:30 hundred hours PM in the afternoon, because I only had 2 hours of workshop time left and I figured it was better spent doing things that can only be done in the workshop.  Reassembling gear cases is one of those jobs I can do in front of the TV while my wife is on her studio time.

After that, it will probably go roughly back together for a test-drive (in the garden and up and down the access lane behind the workshop, owing to England's new lockdown starting on Thursday), and if it drives well, it'll be time to strip it down all over again, consider adding more lightness in the form of relief holes, then cleaning up all the ally components for polishing or painting and reassembling the finished project ready for some track time next year.

Until then, here's some shots of the reassembled truck with the body securely mounted on the nice new sturdy brackets.

[Mad Ax 9313]

I had planned a night in front of the TV last night, so before I picked up my daughter from nursery I whipped the gearboxes out of the chassis ready for strip and clean.

And then I sat down to eat and stuck on a daft horror film and before I knew it it was 10pm, so I still haven't opened up the gear cases.  Well, maybe tomorrow night, then

[Mad Ax 9313]

For various reasons, I've been a bit slow uploading my photos recently.  I'll get to that with a more detailed update in my projects thread sometime over the next few days.  For now, here's what I got up to on Fifty Fifty:

Back on Sunday 8th (when I should have been racing at Stafford) I finally got around to stripping down the transmission cases to clear out the swarf that got in when I cut the top shock lugs off.  And I discovered a divider inside the case that stops any swarf getting in regardless.

Neat job Tamiya - that saves me having to be too precious about sealing up the holes.

I opted for just a little bit of hot glue to keep any dust out.

[Mad Ax 9313]

Fast-forward to Tues 10th, and I figured it was time to start re-making the battery tray.  Actually I jumped the gun a bit here - I shouldn't have added all the sticky-back foam until I was sure everything was cut properly.  It's a real pain to get off and I only had one sheet of it, which is slightly smaller than A4 and doesn't leave much to finish the job.

Here I fitted the foam-covered plastic base from the previous iteration, and also trimmed the rear end panel and glued on a styrene spacer to fit it against the back of the chassis.  Also note a metal spacer used in place of the standard Tamiya ones - these are easier and stronger with minimal weight penalty.

Front buffer from previous version trimmed, and installed

Most of this is just push-fit.  The spacer tube doubles as a battery stop.

[Mad Ax 9313]

Chunky 3S LiPo is held fore and aft by the push-fit stoppers

Here's my sticky-back foam, marked and trimmed with a hobby knife

and installed

is a snug fit, but it can be removed without damaging the cells, so it's all good.  A tight fit is less likely to get damaged, and it's so well shielded by everything it's unlikely it will get punctured on a run.

[Mad Ax 9313]

Test-fit of electricals.  Wiring will be tidied up on the final version.

[Mad Ax 9313]

Sunday 15th dawned dry and bright, so I got up into the workshop for another creative day off.  Unfortunately my wife was unwell so I only got a few hours to myself before I had to come in and take over childcare duty, but this life business is a two-way thing, it's a tougher lockdown than we imagined but we'll get through it.

First thing I did was to drill and cut the slot for my battery strap.  This was harder than it looked, and I made it harder for myself by not stripping down the chassis.  Having stuck on the sticky-back foam, I didn't want to tear it off, throw it away and have acres of gunge to clean off.

So, not the tidiest job ever, but functional