Team Associated CR12 Truck Build

[Nikko85]

Good news the funtek gears slot right in and seem to work! The gear was slightly thinner in profile but seems to he a direct swap with perfect mesh and quiet when running.

So now all I need is another of these and the spur and step metal gear set and all gears will be metal. I've only heard of the shafts warping with big brushless so I should be fine on a 390.

Pretty chuffed I found those, lots of people looking but not heard anyone else making the link as the GPM ones are long sold out! 

 

 

[Nikko85]

2 hours ago, Mad Ax said:

That looks fabulous!  It's got a sort of MTX-1 vibe going on, great stuff  

Thanks! That's what I was aiming for. Really happy with how it turned out.

[87lc2]

That's great, glad you found some gears that work in there.  I was excited when I found these axles a few years back since I needed something as narrow as possible for a scale build but was disappointed with the internals.  Now that I know these are available I'll keep them in mind for future use.  Nice work.

[Nikko85]

On 6/26/2023 at 10:16 PM, 87lc2 said:

That's great, glad you found some gears that work in there.  I was excited when I found these axles a few years back since I needed something as narrow as possible for a scale build but was disappointed with the internals.  Now that I know these are available I'll keep them in mind for future use.  Nice work.

Now the STX gears are sold out, but I have a plan! Either the full diff or something that looks very similar from another maker. 

Here it is with a few other 1/12 scales. The Chevy is probably too small and the Jeep too large, but close enough.

The diff gears will come back in stock soon, I plan to get three of them - one more of the current build, and then set for any future builds. I am also planning to get a higher capacity lithium ion battery (around 5000 mAh) to give some better run times either a 2S2P 18650 or some larger 21700 batteries.

[Nikko85]

The metal pinion and step gear arrived from the not-so-slow boat from China. I am awaiting stock for the second meal diff gear.

Whilst I wait, has anyone got any recommendations for a 390 motor please? I can't see much data on them like I can with 540s and most don't give turn counts.

 

[Nikko85]

The pinion I ordered turned up, the Blackzon slyder pinion. Its 0.6M with a 2.3 mm shaft and quite long so it works a charm.

Here it is on left next to the stock on right. Much longer which helps reach the spur gear.

It is also a much nicer part with better tolerances. The car has an all metal drive train now apart from the prop shafts which seem to be fine from all reviews.

I will charge up a battery and test soon. If no speed increase I could try a 20T 390 I also picked up.

[Nikko85]

Well the 390 motors were a bit of a let down. It's really hard to find specs on these things, but although it had much more torque than stock, it was if anything slower - not helped by a reduction in pinion size. Torque is fun, but getting to top speed in 3m loses appeal quickly. 

So, I did the only thing that made sense, I put a brushless motor in there. My usual small brushless go-to is the Ezrun 2030 - but these have a 2 mm shaft, so I picked up one of these 4 pole motors.

https://www.amazon.co.uk/5400KV-Brushless-Sensorless-Windings-Removable/dp/B08H1T7R3

Now the shaft is a little short, so the pinion now only touches around half the spur gear - which is not ideal, but both are stainless steel, so hopefully won't just degrade despite the smaller contact area. I've turned the brake and punch right down to try and keep the gears and plastic drive shafts safe. I also don't want something uncontrollable either. Wheelies are down, but top speed is right up.

This is where I drive a lot, a large, dusty gravel pitch, so having a good top speed makes things fun.

And fun it was. I kept the EPA to 75% and it worked like a charm. Donuts if needed, but nice slides off power and a great top speed.

I'm not quite sure how the plastic drive shafts or the spur/pinion gear will cope, but I hope having all the settings on low will keep it safe for a while. Certainly it's now much faster than stock, I would probably be happy at 60% power. Perhaps I should just buy the lower KV motor, or I could drop the timing right down for less power and more efficiency.

Out of interest, is there any real practical difference between running a 5800KV motor at 60% vs a 3000KV at 100%? 

 

 

 

[87lc2]

That looks like an absolutely fantastic spot to run the trucks.  The higher kv motor will have less torque so I'd probably run that backed off a bit.  The lower kv motor with more torque will most likely put more stress on the driveline.  I'm no expert, but that's generally how I approach these things (with much larger motors in general) and its served me well.  Let that 5800 turn higher rpm and get more speed with less low end and it should be better on the drivetrain. 

[Nikko85]

17 hours ago, 87lc2 said:

That looks like an absolutely fantastic spot to run the trucks.  The higher kv motor will have less torque so I'd probably run that backed off a bit.  The lower kv motor with more torque will most likely put more stress on the driveline.  I'm no expert, but that's generally how I approach these things (with much larger motors in general) and its served me well.  Let that 5800 turn higher rpm and get more speed with less low end and it should be better on the drivetrain. 

Yes, it's a lovely place to drive, and its almost always deserted. They run festivals in the park, so a few times a year it turns into  car park but usually empty. I've yet to bring jumps with me, but it's large and mainly flat with a nice coating of gravel so you don't get many roll overs and can power slide. Lots of dust and small pieces of rock to get stuck in a car however, fine in the dry and a nightmare to clean off if the car gets wet. 

That's good news with the KV motor and seems to back up what I've experienced. At the moment the top speed is great, but it is not wheely-ing all over the place.

I've seen a video with the truck with a larger lower KV motor and it didn't look fun, and they shredded things quick. Low punch, low timing, low breaks and 75% D/R should keep it alive and more fun to drive. When I went to 100% D/R it just spun out on the gravel and would roll over on concrete. 

Certainly a match for the others in my fleet now. I just need a better on off switch as right now it's two wires I hot wire together to turn on! 

 

[Nikko85]

I took this to the BMX track and it was great - at 75% it's a handful, but it's not extreme - keeps the nose down fine. What's interesting is that this is a much larger motor than those little EZrun 2030 motors I've got for my QD, but I swear they have less power. 

Although the pinion/spur overlap isn't great it sounded pretty quiet - so hopefully it's all fine there.

They've just finished repaving the BMX track, so it's looking great. Always full with BMX at the weekend, but can take a quick trip on a WFH Monday.

As well as tacking the BMX track it was pretty good at the slopes between the tracks, covering quite steep ground easily, which you would expect from a crawler derived chassis.

[OldSchoolRC1]

That looks like a very fun place to run! 

[Mad Ax]

That track looks superb!  The tarmac must be quite punishing on bodies and chassis if you crash, but I'll bet you can have a load of fun there with the right rig.  I'd love to try the LMT on that!

[wolfdogstinkus]

20 hours ago, Nikko85 said:

What's interesting is that this is a much larger motor than those little EZrun 2030 motors I've got for my QD, but I swear they have less power. 

I'm with you on this, I thought I upgraded my brushless QD with a 8200kv motor 2435 size can instead of the 2030 size 7800kv hobbywing ezrun. The EZRUN won hands down.  Bigger motor was topping out at 30mph whereas the EZRUN pushed it past 40 easily and had loads left... hobbywing for the win.

[Nikko85]

So I couldn't leave well alone.

I enjoyed the chevy body but I felt that it looked a little odd in scale.

Having always wanted a proper 4x4 Pumpkin I decided to try my hand at modifying the car a little.

First thing I did was swap out the links for my own made of stainless 3 mm studding, giving a wheelbase of around 210mm or so. I cut down the two prop shafts. These are just plastic, so I may order some metal ones if needed. The motor is the same high KV but somewhat weedy 2435 Surpass brushless. This gives a decent top speed without stressing the drive train too much, so it should be ok.

I made a small box for the electronics, just to neaten them up..

Spray painted the clear coated the body. I added a full interior. I added some livery just using stickers I had.

And here it is

And next to my GF01 for scale.

I am interested to see how it handles. It willI be much more top heavy than stock, but if it doesn't work as an MT I could put crawler wheels and even go back to the 390 motor.

I might need stiffer springs now, we shall see. Hopefully taking out this Thursday on a very rare day off.

 

 

 

[tamiya3speed]

Hey @Nikko85  I’ve had my eyes on the new van version of this chassis and your conversion to metal gears looks like a great idea.  One question though, I can find the Funtek diff gears easily enough but what did you order for the transmission?  

[Nikko85]

6 hours ago, tamiya3speed said:

Hey @Nikko85  I’ve had my eyes on the new van version of this chassis and your conversion to metal gears looks like a great idea.  One question though, I can find the Funtek diff gears easily enough but what did you order for the transmission?  

GPM steel gear for thunder tiger Kaiser which was the first of these chassis.

https://www.gpmparts.com/thunder-tiger-kaiser-xs-steel-45-spur-gear-56t-double-speed-reduction-gears-2pc-set-gpm-skxs56t1233t-p-90079983.html

These things are hard!

[Mad Ax]

That scale is about perfect for a Pumpkin body!

[tamiya3speed]

10 hours ago, Nikko85 said:

GPM steel gear for thunder tiger Kaiser which was the first of these chassis.

https://www.gpmparts.com/thunder-tiger-kaiser-xs-steel-45-spur-gear-56t-double-speed-reduction-gears-2pc-set-gpm-skxs56t1233t-p-90079983.html

These things are hard!

Awesome!  Thanks very much!

[Nikko85]

So an update. I took it out to the park where it drove great, until I heard a grumble in the gearbox and I lost power.

Opened it up to this. I have never seen such a shreaded gear. I can't really account for it. The pinion seemed loose on the motor, but didn't damage the 1st gear. The second gear was a little worn, but that third gear is toast. Any clues as to how this happened? These are meant to be ultra strong steel gears.

Anyway, after that disaster I decided to go back to the original brushed motor and gears.

As well as being worried about a brushelss motor in there the other issue is that shaft on the original motor is really long (14mm) so on any other motor the pinion has to be stuck right at the end and not very stable.

The bad news is that the pumpkin body plus interior was really heavy and I worried about the stock motor, so I swapped out for my lighter JF45 body.

I could go for a tamiya sport tuned 380 in here, does anyone know what turn that is? I did try a 390 that was meant to be fast, but was left very underwhelmed. 

Hopefully this pinion and motor will last. Everything else looks solid. I am loathe to buy more gears for it, unless I can work out how the supposedly super hard GPM ones failed so drastically...

 

[Mad Ax]

That's odd.  On any gearbox I've destroyed, it's always been the spur that fails.  That said, what I would think of as the "spur" on that model is quite small, and that output gear is huge, so maybe that's where the weak point is.

It looks to me like the gear bearings are held in place by the top cover?  If so, any flex in the top cover will allow the gears to move.  IIRC the Top Force has the same problem - when running big power, the top cover can lift up and shred the gears.

Also that output shaft is likely to have all the wobble in it from the propshafts, as well as any shocks coming up from the drivetrain.  Check that your props are in phase - if not, as well as causing uneven power delivery, it could induce an oscillation in the drivetrain which won't help matters.

Is there an aluminium top cover option?  Failing that, is there a way to put a longer bolt right through the gear case and put a nut on the other side?  Looks like you really need that top cover clamped down.

Is there any wobble in those gears at all when it's assembled?  Especially on that output shaft.  Shimming the gears or packing the top case might help.

[Nikko85]

On 12/23/2023 at 7:27 AM, Mad Ax said:

That's odd.  On any gearbox I've destroyed, it's always been the spur that fails.  That said, what I would think of as the "spur" on that model is quite small, and that output gear is huge, so maybe that's where the weak point is.

It looks to me like the gear bearings are held in place by the top cover?  If so, any flex in the top cover will allow the gears to move.  IIRC the Top Force has the same problem - when running big power, the top cover can lift up and shred the gears.

Also that output shaft is likely to have all the wobble in it from the propshafts, as well as any shocks coming up from the drivetrain.  Check that your props are in phase - if not, as well as causing uneven power delivery, it could induce an oscillation in the drivetrain which won't help matters.

Is there an aluminium top cover option?  Failing that, is there a way to put a longer bolt right through the gear case and put a nut on the other side?  Looks like you really need that top cover clamped down.

Is there any wobble in those gears at all when it's assembled?  Especially on that output shaft.  Shimming the gears or packing the top case might help.

Yes, it is all held on with a plastic cover, so I may have just been stressing the case. I think the likely culprit could be the pinion  worked loose (due to the fact it was only placed on the very and of the shaft) which then caused a violent oscillation that threw off the mesh further down the line. The thing is that the brushless motor is pretty weedy, so I am surprised it caused so much damage. The pinion and spur where also fine too.

Many thanks. What would props in (or out) of phase look like please? They have to attach the same way at the gearbox but have options in the way axle side prop does. At the moment they are symmetrical.

Yes I think gearbox flex might do it. It's quite thin plastic, but still seems extreme. I've put more cash into this than any tamiya and still not super happy with it. 

[tamiya3speed]

Maybe worth checking the bearings to see if they are in good shape.  That gearbox design probably isn’t the best for big power being that it is split top to bottom like that.  On a Top Force and CC-01 that have similar issues with big power, a fix is using longer bolts to secure the gearbox halves.  I wonder if a custom skid and something like a Mini-T 2.0 transmission could be made to work?

[Mad Ax]

22 hours ago, Nikko85 said:

What would props in (or out) of phase look like please?

They should be "symmetrical" if that makes sense.  The pins should be aligned like-for-like either end - on most sliding shafts it's possible to pull them apart and slide them together with the pins not lined up, if they are out then a constant input speed will cause the output speed to oscillate, putting a nasty vibration into the drivetrain and making your driver's eyeballs rattle.

[Nikko85]

On 12/24/2023 at 7:51 AM, Mad Ax said:

They should be "symmetrical" if that makes sense.  The pins should be aligned like-for-like either end - on most sliding shafts it's possible to pull them apart and slide them together with the pins not lined up, if they are out then a constant input speed will cause the output speed to oscillate, putting a nasty vibration into the drivetrain and making your driver's eyeballs rattle.

Thanks. They were not lined up so I opened up the drive shafts and spun one end 90 degrees so they were symmetrical!

I ordered some funtek gears for £6 as replacements, I also ordered some small bearings for the step gear/pinion as the bushing has worn from the inside caused by rubbing of the shaft (3mm to about 3.25 mm ID)

I think what happened is the pinion worked slightly loose off the motor and ended up in an non symmetrical rotation. This caused the step gear to massively vibrate damaging the bushing and the next gear on. 

I think now I am just going to run and see what happens with the cheap upgrades. 

If I do enjoy it I can get some more metal gears (I have never heard of anyone else having issues with the GPM) but this is all adding up hugely.

Should it run smoothly and quiet I can explore brushless too, as I am struggling to find a fast 380 motor. However I have so far bought GMP metal gears, two 390 motors, a cheap brushless 2435 and metal diff gears and I've still not got a reliable car or something better than stock!

We like to moan but all my Tamiya just...well work. Yes they need small fixes but I've not shreaded a gear or anything, even in brushless systems in 35 year old Quick Drives. The CW01, MF01X and GF01 all have had zero issues running.

The Team Associsted MT12 has had another body added, so hopefully it is doing well, and this might bring mods, after market spares and fixes too.

 

[Nikko85]

So, I tried with a brushed motor with the FJ40 body as shown, it was a nice little runner, and could be a good crawler, but there wasn't enough speed to make it that fun - the hard body is adding a lot of weight.

so, I've gone down another route.

This is not the exact body I'm doing to use, but very similar shape. I want to recreate the Bigfoot 18 (a car which the Agrios is loosely based on). This will involve a slash or losi 1/16 body painted in blue, with the bigfoot decals I've developed and a few new ones. My hope is to have a very light 1/16 Monster Truck that I can take around a BMX track.

Or perhaps in a slightly different livery. I may cut out some of the rear and then of the shell and cross brace  too.

I'm really not sure about gears, I'm tempted to get the GPM set again, but I want to find out why the last ones shredded first. I'm exploring brushed options on this for now, if I find that lasts well enough with just a little wear then I'll explore another stainless set - something went seriously wrong to shred them so bad, I might just not have tightened something vital (as well as the out of phase oscillation that Mad Axe mentioned).