Fallen's Yeti Jr.

[Fallen]

Well, I have really been enjoying this truck, that I bought off of RCC for my 12 year old son a year ago. It has since become mine, as his full size Yeti is all he can afford to keep running.

As a testament to its durability, I let a father and son, both hobby grade RC newbs borrow it for a weekend camping trip they took, and it came back with zero damage. But, I did a few upgrades before they drove it, as follows:

GPM metal diff locker and axle shafts in rear.
GPM rear driveshaft.
GPM center driveshaft with metal spur.
GPM metal steering rack.

I'm still running the stock open diff in the front, to spare the drivetrain and electronics, which are still stock also. I put 20wt oil in the shocks and swapped in new springs as follows:

Front shocks have Pro-Line scaler upper springs, and HPI Venture upper springs beneath them. I made some camber links out of odds and ends in the parts bin.



Rear shocks have Pro-Line scaler upper springs with the stock front springs beneath them.



The shocks are really well dialed, and since I run 2S LiPOs in this, I added a Venom LV alarm.

I then set about scaling it out a bit. I painted the lettering on the tires. I also painted the rims to match the gold accents on the body. All of that painting was done with Sharpie paint pens. My daughter painted the driver's and passenger's helmets for me.





To add a bit of weight to the rear, along with some Ultra4-ishness I added a spare wheel to the rear. It's just a Slash body mount turned upside down, body clipped into the body and screwed the wheel into that.





I'm pretty stoked on this little guy now. It's fun to drive around inside of my house. My 2 year old sons also love playing with it like its a toy car (which it is). This thing still isn't as cool as my UDR, but I'm really enjoying it.

[smog]

Cool, thanks for the update, don’t hear much of the Yeti Jr these days. Almost grabbed one of these off of the local classifieds, but someone nabbed it ahead of me. Is there much aftermarket still happening for these?

[Fallen]

Yeah, but it's pretty much China aluminum for the performance stuff. There's a lot of scale stuff and chassis upgrades for sale on Shapeways too. Surprisingly, it hasn't been discontinued yet. Horizon still has these for sale on their site.

[Fallen]

I should add that with both diffs open, I really didn't like driving this truck. It would get stuck if you tried to drive over an ant (which is something only a meanie would do).

The stock plastic spur also got clogged easily with sand and dust.

A locked rear and metal spur gear have made this truck fun to drive.

[AC49]

I agree, I have one of these and so does my Brother. Initially I purchased a rear locker from GPM for both RC's and it didn't fit well into the stock housing. When you tighten up there was significant binding that would occur on both rigs. So I purchased the Axial Locker and it fit perfectly. (go figure)
It also turns out once you put some hard miles on it, the GPM locker starts to give away where the dogbone sits in it. The Axial one, no issues.

I did however have great success so far with a GPM rear driveshaft. So... maybe the percision required in the Locker inside the rear axel is just a little more specific than what is in GPM's wheelhouse.

Another interesting finding, one rig we set up with only the rear end locked the other we locked fully. Threw brushless motors in both rigs and they are absolute weapons now. incredibly fast (too much so) but they are a blast to drive. I had thought that the rear only truck would perform better on tracks, but when we race them on an ashpalt oval track, there really isn't a significant difference in their capability, it's more of driver feel.

Great little rig and lots of fun I highly recomend them from a value perspective.

[Fallen]

I actually saw the same binding with the GPM locker. I just ran it and figured that whatever's binding will wear in over time, and its been ok. But I will eventually go to the Axial locker now that I hear it's bind-free.

I think the Axial and GPM lockers are similar in price too.

What brushless set-up are you running? I'm eventually going to upgrade the electronics in this thing, but I plan to keep it cheap.

[Fallen]

Come to think of it, to really keep things cheap I'll probably just replace the brushed motor whenever it dies with another brushed motor. That way I don't also have to replace the RX/TX.

But I still have a steering problem I haven't put the time into solving yet. The servo seems strong enough as I get full throw in both directions when the truck is stationary. But the servo doesn't center very well, so I assume it's binding somewhere. Anyone solved this problem yet?

[Fallen]

Current set-up:



This is a 210mm wheelbase, Tamiya M05 body with a wheelwell massacre. I've had it for years on an M05 chassis. I installed it over the top of the Can-Am body, which you can see under the Mini body in some areas.

I just screwed the body into the rollcage at the existing roof mount locations. You can see 2 of the screw heads on the roof in the photo.

Same great performance. Different look.

[DRED805]

That’s awesome. I have a yeti jr score that my dog got a hold of, and can’t find another body for. Maybe I’ll start looking at mo5 bodies.

[Fallen]

A note about the M05 bodies:

The M05 chassis has three wheelbase configurations, short, medium and long.

The short or 210mm wheelbase is what matches the Yeti Jr. Any M05 bodies that don't say "short" or 210mm probably won't fit.

[Fallen]

Another update:

Since parts for these things are still very easy to find, I put a new motor in mine (stock replacement) for $7 from Horizon. My Yeti Jr. had slowed down A LOT and was burning through batteries, even with being super slow. The replacement motor fixed all of that.

I also swapped out the servo saver spring with a ball bearing (don't know what size) and the steering now has no slop and plenty of power. Even for crawling. The servo also centers nicely now, so I'm not always having to fiddle with steering trim. Considering that I'm still running the stock plastic steering links and servo link, I don't think I need a servo saver.

And I put my FPV system back in it. These little trucks are cool!

[Fallen]

Well, here it sits now:



Those are the 1.55 RC4WD aluminum Wagon Wheels with Mickey Thompson Baja MTZ tires. They're WAY too big to fit under the Mini Cooper body, so back to the UTV I went.



Those tires are a significant performance upgrade. Even with the stock, open front diff my Yeti Jr. rarely meets an obstacle it can't crawl, or at least hop over. The stock motor does notice the weight and size of these wheels / tires though.

Speaking of heat, you may be wondering why my UTV body looks like its had it's front teeth knocked out. It's partially because my 3 year old sons LOVE playing with it, and had partially ripped the grill off already. The other part is that I wanted to add some cooling for the FPV system.





That system runs off of the XH plug for my 2S LiPOs and it gets hot, about 150 degrees. I mounted the video transmitter on some 1/2 inch standoffs so there's a gap between the lexan and the transmitter but it still gets hot. I suppose it's designed to run that way, but I wanted it to breathe a bit.

Now you're also probably thinking the Can-Am body has no problem getting airflow under the body. And that would usually be true, except that I installed the R-Design inner fenders Shapeways sells.





The install for this wasn't straightforward. I had to pull screws from another part of the Yeti Jr. to make it work. And I cut the battery tray portion of the fenders off, as I'm quite happy with the stock battery tray.

Well enjoy your Yeti Jr's. I'm amazed that they're still in production, stock parts are still very cheap and that mine is still so fun to play with.

[DRED805]

Those wheels and tires are siiiick!

[Fallen]

Thanks! They look sweet, and really do perform well.

I bought them used off the forum here, so I don't know fur sure which foams are in them. But I assume they're the stock RC4WD foams which are great for the weight of the Yeti Jr.

With my open front diff, mine drives better as an Ultra 4 car than a crawler. But with 2 locked diffs and these tires, you'd have a decent little crawler.

[DRED805]

Originally Posted by Fallen

Thanks! They look sweet, and really do perform well.

I bought them used off the forum here, so I don't know fur sure which foams are in them. But I assume they're the stock RC4WD foams which are great for the weight of the Yeti Jr.

With my open front diff, mine drives better as an Ultra 4 car than a crawler. But with 2 locked diffs and these tires, you'd have a decent little crawler.

You bought them from me… haha. They’re just the foams that came with the tires.

[Fallen]

Rad! You'd think that at 40 years old, my memory wouldn't be so short. I suppose 5 kids and working as a patrol cop will do that...

And thanks for the clarification on the foams. These tires really make me want to drive my Yeti Jr. more.

[Fallen]

Well, this is how it'll probably stay for a while. I trimmed the UTV body down to just an interior to make it fit better. So until I get a new UTV body, the Offroad Mini will be tearing up the dirt.

I decided to murder the wheelwells in order to make these larger tires fit. To hide my killing, I made these fender flares:





They're some cut-up Tamiya road tires, glued to the body with tire glue. It's an ugly, goopy job but this Mini won't be winning any beauty pageants anytime soon anyway.



I've sacrificed about 1mm of up-travel in the front, and about 3mm of up-travel in the rear. I don't think I'll miss it much.



Whenever I buy a new UTV body and get it painted up, there will be more photos to come. Unless I booger the paint job, and I'm too embarrassed to post it.

The downside to this Mini body: to flip the body up for battery changes I either have to remove the rear wheels, or remove the hinge point screws to totally remove the body. Either way is two screws. I'll figure something better out eventually...

Go build or drive something!

[Fallen]

Comment & a question:

Comment: These Baja MTZs work GREAT in the sand. I'm sure being taller than the stock tires helps too, but man is my Yeti Jr. is faster in the sand now. It also does much less getting stuck.

Question:

Something I notice when driving in sand ONLY: either the ESC or motor temporarily dies after some hard running (100% throttle, driven wide open for 5-10 minutes). The steering will still respond, but no response to throttle inputs FWD or REV. After 15 or 20 minutes, everything is fine.

It sounds like an overheat condition, but I can still touch the motor without having to pull my finger away (not precise, I know). Maybe the ESC is overheating? Or maybe it's time for me to finally upgrade to brushless...

[Fallen]

Disregard my last question. It's surprising what a glance at the manual will do.

Apparently the ESC DOES have overheat protection, and that's what I'm seeing in the sand. Tall tires, heavier wheels and powdery sand? Sounds like a recipe for overheating stock electronics to me...

[DRED805]

Any brushless systems you're looking at in particular?