Yeti Jr Success Story

[Mendoza]

Hey everybody!

I know the Yeti Jr has been much maligned and a bit of a PITA OOTB, but I wanted to post up my experience since buying one for my sons 5th Birthday which happens to be on the 16th December in 2017. This ‘relationship’ started in tears and anger but has turned into something great and this story is my therapy "thumbsup".

It arrived after I purchased it from amain (my #1 HS) we turned it on a week before Christmas and sure enough, like everyone else esc, servo ... EPIC FAIL!

Son was devastated, I wanted to make his 5th memorable and he was the envy of all his mates when they initially saw it, but when it stopped working within 5 mins I was pi$$3d...

I basically had 9 days before Christmas to get it back (adding to the stress was holiday season delivery logistics to Australia!!) ... And so it begun ...

 

[Mendoza]

I went deep into research mode and thanks to some seasoned crawlers on this forum like ‘Screamer’ and a few others I started to build the BOM (bill of materials) which ended up like this:
Hobbywing 1080
GPM lockers x 2
GPM center driveshafts
GPM steel rear drive shafts
Hitech mighty servo

I wanted to build something durable and with as minimal mods as possible and placed the order with amain.

 

[Mendoza]

I ended up paying USD$30 just for postage to get the stuff in time and as usual amain got it done... I thought FANTASTIC! I will be my sons hero again -problem solved .. 5 days before Christmas - happy dayS :ror: ... BUT NO...

I initially tried the spectrum radio and receiver out of the mini 8ight T with the 2S Lipos I had from my old mini LST and the HW 1080 esc but within 5 mins the hitech mighty mini smoked up and fused up :evil: ...

So I thought it’s a faulty servo... no time for an amain return, let’s go to my LHS and pay top dollar for a like for like replacement 3 hours later (including the drive) another smoke up and burn out :evil:

I was following ‘Screamers’ idea of keeping the weight down and slotting a servo straight into the old spot... but it wouldn’t play ball... so after wasting time and money I pulled the pin on the mini 8ight T radio gear and dug deep into my Mini LST bag of tricks and summoned up some of that hobbyist creativity ...

 

[Mendoza]

3 days before Christmas I had no choice - time was running out and my son really disappointed! I was going to have to run a different servo and radio gear.

So out came gen 1 ... 2.4GHz radio and receiver from the LST and I pulled the spectrum mini servo out of the mini 8ight T (great torque and slightly smaller than a full size servo). Tested this set up and finally ... NO SMOKE! :mrgreen: but now I had to make it fit in the Jr chassis.

Grabbed some of my aluminium plate left over from my custom mini LST single servo mod and went into design mode. Created the pattern, attached the servo to the underside of the plate and then attached the plate to the rear chassis. Some bending of threaded rod and a couple of old ball end cups with minimal Dremel work to the chassis and we finally had a new battery plate and functional servo with more grunt than would ever be needed. ;-) I felt good but boy it took some time to get to this point and it was Christmas Eve!

 

[Mendoza]

Even though I had the Hop-ups ... at that stage of my sons rc experience I decided not to put them on. To my delight and after much heartache I put this under the Christmas tree with a couple of charged batteries and my son was really excited to drive it.

I wanted to observe the chassis and durability of this vehicle so I let him run it with stock drive shafts, and open diffs. Which has lead me to this post today... after almost a year of bashing including drop offs and front on collisions with brick walls, rocks and trees the only failure we have had was weirdly a shortening or shrinking of the main drive shaft (spur to rear diff) which caused it to pop out constantly.

It was time to pull out the hop-up parts and get to work.

 

[Mendoza]

So almost a year later I have now ...

Installed the GPM center driveline (its fantastic and fits beautifully)
Installed rear locker but retained plastic driveshafts to keep down weight
Installed scx10 40mm front springs (super soft)
Installed RC4WD Dik Cepek 1.55 tires (lowest weight I could find) on 1.9 wheels
Regreased and relubed entire vehicle
Rebuilt shocks/refilled with 25w oil. Used plumbing tape on threads to stop leaks

 

[Mendoza]

To close this off, I just wanted to say that I was as annoyed as anyone else at Axial for the poor electronics and servo but the chassis dynamics and build quality are good and it’s a durable little truck especially after being in a 5yr olds hands for the past 9 months-much of the time unsupervised. When you dial in the suspension right it handles well. The best upgrades that have taken it to another level of drivability and durability have been the center drive shafts and the rear locker and the Cepek tires are phenomenal... Left the front diff open as locking the rear makes such a huge difference. My son loves this and compared to all his friends toy grade Rc’s the yeti Jr is KING... speed, handling and crawing are in a different world.

I don’t think Axial were far off producing an excellent 1/18 scale rc. Like many others have said, if it came as a roller and rear locker at a lower price point it might have really taken off.

I’ve tried to future proof it for my son but with the added weight I’m worried about the motor even though it’s been great. He gets 25 - 35 mins run time on 1600mah LiPo and the motor gets up to 70 degrees Celsius. I’m still only allowing him 75% speed and got it set at 80% drag break. The negative is there doesn’t seem to be many alternatives in the brushed motors this size for replacement. Wish I could buy 2more of these axial 40T motors but can’t find them. (Any RECOMMENDATIONS ON BRUSHED MOTORS WOULD BE APPRECIATED?)

This though is definitely a happy ending... :ror:"thumbsup"

 

[Brake Weight]

Are you still using the stock motor? This was an annoyance to me as finding another brushed motor that fit was fruitless. I found that the Redcat MOA motors fit but I ended up going with a cheap sensorless brushless. On flat surfaces it takes off like a rocket but in grass you have to kick start it due to the cogging. I may go back brushed with the next size down HobbyWing ESC.

 

[Mendoza]

Hey Bud.Still running stock motor but I fear for it. Temps reaching about 160 after a long run. The Redcat motor from the 1/18 volcano was one I was looking at too. Looks like it’s got the speed but not sure of the quality. There are also some Tamiya brushed ‘tuned’ motors that might work.

The axial motor that comes with it is surprisingly good. I’d almost buy 3 and stock pile them if I could find anyone selling them.

 

[corey.gray.921]

Hey Bud.Still running stock motor but I fear for it. Temps reaching about 160 after a long run. The Redcat motor from the 1/18 volcano was one I was looking at too. Looks like it’s got the speed but not sure of the quality. There are also some Tamiya brushed ‘tuned’ motors that might work.



The axial motor that comes with it is surprisingly good. I’d almost buy 3 and stock pile them if I could find anyone selling them.

I think I have a motor, I also built my jr yeti with up grades. Are u using the stock gears also with this 1.55 tires ?

 

[Mendoza]

Yep. Stock gearing with the stock motor and these 1.55 tires. Have you got any advice regarding gearing and motor choices? I found out the redcat 370 is not an option too small.

 

[Brake Weight]

Some were using the Losi Mini pinions. I didn’t have much luck with brushed motors due to the Axial motor having a small shaft compared to the Redcat motor. Plus the Axial is a little shorter.

 

[Mendoza]

ok so I am excited to have found 2 brushed motors with the same can length, diameter and shaft size...

Associated CR380 Brushed Crawler Motor ASC27422 And
Dynamite DYNS1210 - 25T

I’ll pick up the dynamite and give it a go. I think the increase to my tire diameter (running the 1.55 on 1.9 wheels) has put additional strain on the Axial motor which is why I’m getting higher temps.

 

[odomandr]

This is great. I've really enjoyed the jr I bought too. It is a blast and has been durable for me too once I swapped in a sidewinder micro, spektrum radio and hitec mini servo. I've yet to break anything and had definitely run it into some walls and posts.

I experienced some serious heat when I put the rock racer tires on my score truck. The gearing was wrong but it's faster and gets through tall grass better.

I too have looked for another motor. Looking forward to hearing about your experience with those

 

[Mendoza]

Got home from work today and find my son had driven it through his Sandpit. Not normally a problem but our sandpit is about 3 x 3meters and it’s been raining heavily, so it’s basically been full of water - deep enough to submerge the yeti jr up to the drivers.

Me: what happened son
Son: I was driving it through the sandpit and got stuck
Me: did you pick it up
Son: No I was going backwards and forwards turning the wheels like you told me to do when I get stuck
Me: then what happened
Son: it stopped working
Me: sigh!
Son: you said it could go through water
Me: yeah ... slowly

:lmao::lmao::lmao:

Can’t help but laugh, he’s 5. Anyhow the motor was literally full of wet sand and sludge, seized tight. Whole drivetrain was seized. Spectrum servo jittering.

I pulled the rig down again, hosed the motor out with high pressure water, then soaked it in WD40 and then blew it out with a high speed blower.

Unbelievably this survived another torture session from a 5 yr old ... Surprisingly that little stock motor is quite heavy and still going strong after that-no performance degradation! It’s such a shame that Axial has fallen. Hope horizon keep the designers and engineering team.

 

[Mendoza]

We’ve been running the rear locker with the stock plastic shafts... one gave way today. Changed them out for the GPM steelies... son ran it for 45 mins non stop and the added weight helped on the rocks... motor ran really well.

 

[Mendoza]

Also got him a set of CI foams. I’ve never used these but now I see why people rate them so highly. Fill the tires out beautifully and really perform on the rocks compared to standard foams. I’m getting a set for the spawn.



Check out the difference mounted up

 

[Mendoza]

Just thought i'd take some footage of my Son driving through our yard. We tried to do one 'take' but had to do about 10 in the end and hack the footage together to make it more watchable. The sandpit water level has dropped and I've taught him to drive through it nice and slow :lmao: ...

ESC 75% speed and 80% drag brake. Still haven't given him full power!

<iframe width="560" height="315" src="https://www.youtube.com/embed/GSc5-vKgfTk" frameborder="0" allow="autoplay; encrypted-media" allowfullscreen></iframe>

 

[Lugnutt]

Can you post some pics of how u mounted that servo, I just got a jr and want to do something like that mod

 

[Mendoza]

Yeah I’ll post you up some pics if you need more than what is already there? I’ll need to see if I can take some closer shots of my sons jr. in summary it’s basically an alloy plate secured to the original battery holder and front gearbox case with thru bolts and spacers. I then mounted the servo as per pics to the underside of the plate using 90 degree servo mounts and then bent a threaded shaft to get the range of steering motion. My advice is go with a plastic servo horn and don’t screw it down so it pops off on major impacts. It’s trial and error in terms of steering geometry but this custom set up has been rock solid, adds weight much lower and central compared to the other 3D mods on this forum and stiffens up the chassis. And still no failures with the plastic gear spectrum servo (out of a mini 8ighT truggy) with my 5yr old son beating the crap out of It. It also crawls and bashes really well with the locker in rear and this chassis set up. I don’t get on this forum very often but I’d be interested to see your progress. Good luck!