2 Speed or not 2 Speed, that is the question.

[CoolRunning]

The Bomber/Yeti 2 speed trans is reportedly really reliable. That's what I'm running in my 2 speed Bomber and my Yeti trans (which is old as the hills) is still in mint condition inside (bearings were in great shape) even after a few previous abusive owners. I am though running an SSD SCX10/wraith 2 speed in the SCX10.1 and it's a great piece of kit (all CNC and high quality) but it's probably too high and will take up some interior.

The stock Yeti/Bomber trans can also be beefed up with HD gears if it somehow breaks with a crazy powerful motor. That's probably the cheapest thing to try (you might be able to get one second hand) and the 2 speeds sometimes are on special (the Axial kit has a good shifter arrangement) and you can get an optional gear for low from SSD that reduces the ratio further if it's not slow enough.

[MAC FAB]

Thanks CoolRunning. I'm reaching out to the TRX-4 community right now as well, as to if its embraced or hated. $50 on flea bay and it looks small. Those here who say "NO 2 SPEED!", how do you think your rig would work if you actually had one in your rig with your current motor/esc setup? I'm a newbie to crawling, so any advantage is welcomed to overcome lack of crawler driver talent!

[clm]

Originally Posted by MAC FAB

Thanks CoolRunning. I'm reaching out to the TRX-4 community right now as well, as to if its embraced or hated. $50 on flea bay and it looks small. Those here who say "NO 2 SPEED!", how do you think your rig would work if you actually had one in your rig with your current motor/esc setup? I'm a newbie to crawling, so any advantage is welcomed to overcome lack of crawler driver talent!

Well, I like my TRX-4s 2 speed. It is however a very polarizing subject, I have heard TRX owners who like the features, and I have heard people planning to get a TRX and then remove all the features (2 speed/lockers). Once you strip all the features off, it is basically just like any other trail truck without anything special about it.

[MAC FAB]

Originally Posted by clm

Well, I like my TRX-4s 2 speed. It is however a very polarizing subject, I have heard TRX owners who like the features, and I have heard people planning to get a TRX and strip all the features off, it is basically just like any other trail truck without anything special about it.

Strip the widgets, what? Those are the reasons to buy it!!! What kinda mph in low as well as high using what battery? Looking for spread. Have you driven it hard fast to attest to the durability of the part?

[clm]

Exocaged is the one you want to talk about in that regards, I am still using stock motor and speed control and I'm stuck to the 6 cell nimh for the time being that I use in the vintage cars. I have run it on a 2s lipo at the hobbyshop when I first got it but just for a bit.

Exocaged beats the living snot out of his TRX-4 with brushless and 3+ cell lipo.

New batteries are on the list for mine, but only 2s as they also need to work in the Summit converted Revo. Stock Summit esc's will only take 2s or 7cell nimh. Although a new steering servo comes first. Wheelin on a budget... whee

[DukeMinnix]

Originally Posted by MAC FAB

Those here who say "NO 2 SPEED!", how do you think your rig would work if you actually had one in your rig with your current motor/esc setup? I'm a newbie to crawling, so any advantage is welcomed to overcome lack of crawler driver talent!

Id say your trigger finger discipline could be a little more lax with the 2 speed and low gearing option. I know since I installed my roc412, I'm more likely to goose it instead of trying to correct my line and be more technical. A slip of the finger would be more forgiving with doubled gearing.

[MAC FAB]

It's a good thing I don't impulse buy. Last night I was really leaning toward the TRX-4 tranny, really considering it. After sleeping on it, and thinking about where I will be driving this, I think I can get by without one. Nothing that technical. Then I had a second thought, what if I need a little more oomph than I can get from low gear to climb up something, which is what Maslin and others were indirectly trying to get into my head. I can go center mount on the motor, with the motor up high for an easy pinion change and I can still run 48 pitch gears that I like. Crawler mode say 18 mph top end, Trophy Truck mode go up a few teeth. Too easy. Build an aluminum cover or vacuum form one for the motor and go drive. A lot less headache that way and I can get my build done. So now convince me why I should put a tranny back into it.

[MAC FAB]

One more question. Anybody run 2s batteries with a 2 speed? I'm leaning hard tiwards that again, liking the TRX-4 unit a lot.

[clm]

I run 6 cell nimh at the moment with the 2 speed TRX, mainly because I have no large Lipo...

[DavidH]

Originally Posted by MAC FAB

One more question. Anybody run 2s batteries with a 2 speed? I'm leaning hard tiwards that again, liking the TRX-4 unit a lot.

To be clear the stock Summit requires a pair of 2s batteries. The servos and rx see 2s, the motor 4s.

Originally Posted by MAC FAB

It's a good thing I don't impulse buy. Last night I was really leaning toward the TRX-4 tranny, really considering it. After sleeping on it, and thinking about where I will be driving this, I think I can get by without one. Nothing that technical. Then I had a second thought, what if I need a little more oomph than I can get from low gear to climb up something, which is what Maslin and others were indirectly trying to get into my head. I can go center mount on the motor, with the motor up high for an easy pinion change and I can still run 48 pitch gears that I like. Crawler mode say 18 mph top end, Trophy Truck mode go up a few teeth. Too easy. Build an aluminum cover or vacuum form one for the motor and go drive. A lot less headache that way and I can get my build done. So now convince me why I should put a tranny back into it.

Did you not say earlier that you didn't think that the 2.3:1 spread of the axial transmission was enough for you?

It comes down to how you plan to use it; I didn't really know when I bought my yeti last year.

I finally got my IFS/IRS yeti out, between the rain clouds, and I think I am still good with the speed and gearing; I am looking forward to trying the sensored operation of the new motor. Sensored is not a substitute for proper gearing, but you might find, if you only crawl a bit, that the sensored operation is sufficient for your needs. Dunno yet. The 2-speed axial certainly allows me to crawl with the factory motor without cooking it.

What killed me was how bad the factory rock racer tires were for speed on the factory foams . The top speed was unusable, night and day compared to the 2.8" tires and wheels I had on previously.

What kind and how tall will the tires be that you plan to use? That will affect gearing and the range of usable speed and handling. Will you switch to taller tires for crawling?

[MAC FAB]

Originally Posted by DavidH

To be clear the stock Summit requires a pair of 2s batteries. The servos and rx see 2s, the motor 4s.


Did you not say earlier that you didn't think that the 2.3:1 spread of the axial transmission was enough for you?

It comes down to how you plan to use it; I didn't really know when I bought my yeti last year.

I finally got my IFS/IRS yeti out, between the rain clouds, and I think I am still good with the speed and gearing; I am looking forward to trying the sensored operation of the new motor. Sensored is not a substitute for proper gearing, but you might find, if you only crawl a bit, that the sensored operation is sufficient for your needs. Dunno yet. The 2-speed axial certainly allows me to crawl with the factory motor without cooking it.

What killed me was how bad the factory rock racer tires were for speed on the factory foams . The top speed was unusable, night and day compared to the 2.8" tires and wheels I had on previously.

What kind and how tall will the tires be that you plan to use? That will affect gearing and the range of usable speed and handling. Will you switch to taller tires for crawling?

I am trying to build this thing as inexpensively as possible, just in case it DOESN'T crawl for beans, hence $60 gets me a trans and motor mount.. Dimensionally I'm duplicating my go fast program. Tires are Yeti SCORE TT tires, about 4-3/4 o.d. I am 99% sure this thing will blaze at speed. Spongy crawler tires won't work for speed just like what I have isn't ideal for crawling. Gearing will be figured by a calculator. Not running the Summit motor, rather a 550 can CC 2400kv and Mamba Max speedy.

[MAC FAB]

Part 2 of the mini novel from above^^^^^^^^. If it does crawl like a spider, V2 would be parts spec'd accordingly. Something else that is going through my head is relieving gears so I can shift on the fly. Probably not a good idea , and may not need to do it either. Anyhow, just got back from vacation so I'll get back on this thing shortly. As always, advice/criticism is always welcome.

[clm]

My TRX-4 shifts fine on the fly, the gears are always meshed and the shifting is by shift dog engagement like a motorcycle. Might eventually break the dog or the engagement ears on the gears... but someplace will be the weak spot.

I just picked up an Everest 10 trans for my crawler project off ebay a few days back for a little over $14. It's basically a KO of the axial scx10 box. I am building an outside the box crawler and I don't know if it is all going to work yet so I am avoiding buying high end parts

[MCE Jason]

I run 2 bombers set up for U4 racing. They both have HH censored brushless setups. One is set up with a SSD 2 speed, geared it to race in high gear. It defiantly performs better in low gear than the non 2 speed bomber. My boy loves to crawl/ trail/ race, the rig is more versatile with the 2 speed over the other without.
good luck

[MAC FAB]

So I've gathered that a 2 speed will best serve the end reslts I'm looking for. That said, I'm about to the point again where I'm just going to put the center mount deal I have and gear it accordingly and be done with it. 20 ish mph on the top and go crawl. It is such a PITA to try to mix and match parts without actually having them in my hands, pondering how I'm going to make it fit and not have a surplus of unused and useless parts. Virtual reality building? Then I'm running out of room to put a battery as well. I know what I want in the end, just don't know how to get there. Can always do a v2, right?

[DavidH]

Originally Posted by MAC FAB

So I've gathered that a 2 speed will best serve the end reslts I'm looking for. That said, I'm about to the point again where I'm just going to put the center mount deal I have and gear it accordingly and be done with it. 20 ish mph on the top and go crawl. It is such a PITA to try to mix and match parts without actually having them in my hands, pondering how I'm going to make it fit and not have a surplus of unused and useless parts. Virtual reality building? Then I'm running out of room to put a battery as well. I know what I want in the end, just don't know how to get there.

Indeed it helps to have the parts. I used old servos, a cardboard mockup of the battery tray, and I had a yeti from which I could pull the transmission dimensions from. As it turned out, I had only millimetres with which to play with, keeping to the factory wheelbase and a standard servo for shifting. If I want to shorten the wheelbase, the servo would need to be changed or relocated.



If you need any dimensions off of the yeti-bomber transmission, let me know.

Can always do a v2, right?

I'll do as many as I have time and money for.

[MAC FAB]

What is the footprint of that tranny, how tall, output shaft size and length from output to output? I'll really know better when oi have a complete roller, with the diff servos mounted. Will a micro servo run the 2 speed? I'd be taking it from my Summut, which will be non locking and probably single speed when I'm done taking parts from it. Any good pics showing all views would be appreciated as well.

[DavidH]

Post it here, or in your build thread?

[MAC FAB]

This is probably the best place. What is anyone else running, lets see it with specs.

[DavidH]

A - rear 5mm output shaft 0.35"
A (the middle one, as I am not gonna edit the pic again ) case length 3.5"
B - front 5mm output shaft 0.35"
C - output centre to widest part of transmission case 2.0"
D - output centre to outside transmission case 1.7"
E - output centre to edge of motor mount 1.2"
F - output centre to edge of spur cover 2.5"

Note that the bomber comes with a different transfer case, with a longer output shaft for the rear axle.

The yeti pan aligns the transfer case output with the centreline of truck, while the bomber is offset, more in line with the AR60 axles.

My design pushed the transmission to the left a bit to allow the front servo and battery to be pulled closer to the centreline.

The shift servo (>80 oz in) hypothetically could go anywhere on the truck, if you were willing to use a pushrod or bellcrank system.



G - height from pan to top of motor mount 2.7"
H - overall length w/o output shaft 4.8"

Time to get me a metric dial calliper, being Canadian, and all that.