need help wit new wormanatior

[zoojunkie]

Save you some trouble, read below what I posted on RC4WD's forum about their ARTR Worminator I was building for a friend.

Hi all,

The purpose of this thread is document a single problem with the design of this ARTR my friend purchased from a local hobby shop.

The biggest problem with the ARTR Worminator is the drivetrain.
Here are the spec's for the power source.

Novak Ballistc 3S ESC with their 18.5 Ballistic motor.
Turnigy 1300mah 30C 3S.

Using the stock 28T and 1:1 transmission, the temperature of the motor hits 240F, well over the 160F Novak recommends. On top of that, this motor temperature was taken after 10mins of crawling. Another issue with the stock 40:1 gears, is that when the wheels bind, the entire load of the bound wheels needs to be overcomed by the motor, which is part of the issue of why the motor heated up so fast in such a short time. There is no mechanical advantage in the transmission to assist the motor from cooking itself.

Switched to a smaller pinion (RC4WD only supplies you with the 28T pinion), installed a 23T (couldn't fit a 21T). The 23T helped with the overall drivability of the ARTR, but the motor still exceeded 160F, and the run time was only 11mins. Way less than a Losi Comp Crawler on a brushed handwound JPCustom motor, and we're running a brushless!! Way less than a Rock Force with a Holmes Cobalt 7T.

On to test number 2.
Switched out to the 25:1 gears, with the 23T pinion still installed, and we lost all crawling torque. The ARTR was unable to climb a vertical face (laminate wood flooring and a refrigerator face).

After fooling around with the ARTR for several days, I am unable to get this thing crawling any where near any of the other worm gear driven crawlers (I have both LCC and RF to compare it to).

Solution?
Because there is no mechanical advantage on the motor side, and all the reduction is in the axle, when the axle binds, it requires an enormous amount of power to over come. More than any inrunner brushless motor could ever provide. I suspect a 1/8 scale brushless motor maybe the ticket, but I'm not going to spend that money just to test it out when the mfg should have had this already done.

My last solution was to test these axles without the 1:1 transmission. I installed the axles (25:1 gears installed) in my AX10, installed my buddy's Novak, and a 21T pinion w/ the stock 87T spur. Overall? Way more efficient, I am able to get more than 20mins of run time and my motor temps NEVER exceeded 100F. However, the draw back to installing these axles to an AX10 transmission is the lack of wheel speed. It was slow and a blip of throttle didn't give me a surge of forward speed. In the end, the AX10 transmission plus the 25:1 regeared worminator axles, worked MUCH better than with the 1:1 transmission.

What the stock ARTR Worminator needs is a slight reduction, a 4:1 or 5:1 transmission would be ideal for these axles with the 25:1 gears.

We've been regretting telling our friend to buy this ARTR given the fact that the drivetrain is completely useless with these axles. Even w/ the regeared 25:1, I was unsuccessful in getting this ARTR working well enough to hand it over to our friend. I've been very disappointed in this kit.

The only way now for me to build this ARTR right for my buddy is to have him purchase the 4:1 motor reduction RC4WD sells, but WHY? Why am I forced to have my friend purchase something that should have been fine from the get go? I completely understand the whole DIY ideology of crawling, I've fabricated a few chassis for myself, but requiring a novice or an expert RC hobbyist to experiment with drivetrain to get their brand new crawler working at 100% is on the scale of fail.

Stock ARTR Worminator needs a redesign in the drivetrain. The notion of having all the reduction in the axle is flawed. The motor requires mechanical advantage 1. for less load 2. for more efficiency.


If the customer service for RC4WD is reading this please contact me. I would love to make this ARTR Worminator perform and be able to hand it off to the owner with a smile rather than "Shit buddy, we're sorry we told you to buy this POS, good luck with it!"


I've spent 2 weeks since new to get this drivetrain ironed out. Still no luck.

[zoojunkie]

Our fix?

We purchased one of these: http://www3.towerhobbies.com/cgi-bin...P?I=LXVLE9&P=8

slapped it on his Worminator and it was good to go.


My big beef about this entire process was why did I have to as a consumer have to purchase something else to make their ARTR work?? If I'm paying $400 for a ARTR crawler, I expect it to work without it killing my electronics. It's sad how little thought they put into the drivetrain for this vehicle. Now I have to wait till they come up w/ a solution and we still haven't heard much from RC4WD.

[shelljeep]

At least you got it going for him. Good on ya.
I'm hopng my LCC tranny does the trick for me.

How is the turning angle on these axles compared to the LCC axles?
Did you look at the axleshafts? Beef or meh?

[Sharkey]

that 7.4:1 reduction box puts you at 185:1, i dont really think thats the answer. its all in the final gear ratio, its nothing to do with were the reduction is happening, in the tranny or in the axles. 25:1 deffinitly wont crawl, like i said earlier, 40:1 is still too tall, although might work with a 1000kv outrunner brushless. right now im running 58:1, i think somewhere between 50 and 70:1 would be what you need to shoot for.

rc4wd does make a 2:1 reduction unit, with a 1:1 transmission that would put you at 50:1 or 80:1 depending on the axle gearing. either would certainly work, although with 80:1 your going to want some decent power to get the wheelspeed (brushless and 3s, or maybe a 7t cobalt puller). ideally rc4wd should build the axles with a more friendly ratio, such as 50:1 to use a 1:1 tranny, or build a tranny gearset to be around 1.5 to 2:1.

[zoojunkie]

Originally Posted by Sharkey

that 7.4:1 reduction box puts you at 185:1, i dont really think thats the answer. its all in the final gear ratio, its nothing to do with were the reduction is happening, in the tranny or in the axles. 25:1 deffinitly wont crawl, like i said earlier, 40:1 is still too tall, although might work with a 1000kv outrunner brushless. right now im running 58:1, i think somewhere between 50 and 70:1 would be what you need to shoot for.

rc4wd does make a 2:1 reduction unit, with a 1:1 transmission that would put you at 50:1 or 80:1 depending on the axle gearing. either would certainly work, although with 80:1 your going to want some decent power to get the wheelspeed (brushless and 3s, or maybe a 7t cobalt puller). ideally rc4wd should build the axles with a more friendly ratio, such as 50:1 to use a 1:1 tranny, or build a tranny gearset to be around 1.5 to 2:1.

You might want to revisit your thought

its all in the final gear ratio, its nothing to do with were the reduction is happening, in the tranny or in the axles. 25:1 deffinitly wont crawl, like i said earlier,

, I have a lot of test time with this and data on this. With the 25:1 gears only and a 1:1 transmission, it will not crawl. With the 1:7.4 gear reduction, it will crawl AND the motor temp is well within spec of what Novak wants. The motor needs mechanical advantage, without it, you WILL overload a brushed 3 pole motor and over heat a brushless because of the load the motor sees.

You should test what I documented above on a Worminator axle w/ 25:1 gears and a 1:1 transmission, your LCC transmission will not help you, it's .87:1. The motor got hot because of the load applied to it when it is used with the 1:1 transmission with either the 40:1 or 25:1 gears. We can consistently roast a 3 pole brushed motor in a LCC when a single wheel is bound up. Why? It's too much load to the motor AND the motor is shorting because the brush and comm are static.

This I do agree with

ideally rc4wd should build the axles with a more friendly ratio, such as 50:1 to use a 1:1 tranny, or build a tranny gearset to be around 1.5 to 2:1.

Ideally with the 25:1 A 4:1 transmission would work well with a 18.5T brushless motor. Using a brushed motor 3 pole or 7 pole (cobalt) is woefully lacking in run time because of 1. brushed motor's inefficiency and 2. inefficiencies in worm gears.

[JesterSpec]

As stated, binding the motor is binding the motor. Gear reduction is still gear reduction, if its in the tranny or in the axles, its still in the drivetrain. The ultimate is the final gear ratio, This will set the RPM/tq load on the motor.

The point is, you don't need any tranny reduction if the worm's are setup with the correct reduction.

On an ax 10 you get reduction in the Tranny, and again in the diff. This spreads the work. Partial bind in the Driveshaft/output, and partial strain on the axles. On anything with a 1;1 tranny where all the reduction is in the axles, the stress is ultimatly on the axles (between the diff and the tire).

Yes, Talking with fred there are a ton of drivetrain issues with the worminator. If you have the time, patients, and parts I believe that it can be made work.


My question is, you raise the reduction in the axles and tranny, then lower it again with the reduction box. What point does that serve?, Its like putting in a 4:1 atlas, and running 3.55 gears, its lowering your wheel speed, then raising your wheelspeed. The only reason I would do that to my 1:1 is to keep the pinion slightly larger for strength.

[shelljeep]

Originally Posted by BansheeManiac

Will do, i'll start one with pics tomorrow, t-boner is my neighbor.

Waaay past tomorrow man.

[BansheeManiac]

LOL sorry about that, been busy. Lost my job, looking 4 another.but I have a question what size shocks is best to use on the artr? Axial seem way to big.


Lmk, thanx
Lance

[shelljeep]

I'm researching this also, for my Losi MOA build.
I'm using the 4" Losi aluminum shocks right now, they don't leak instantly like the plastics. I like the availability of different spring rates, and pistons. But I think you can use any roughly 1/2" dia. spring of whatever rate/length you want with most of the other 4"-ish shock bodies out there. And you can redrill shock piston ports also. So, availability of upgrade options probably isn't a sound reason to stick with them.
Just haven't learned enough yet to see if there is better shock body out there yet. There probably is.
I was thinking about a longer shock, but 4" seems right for 1/10 ride height, I like to stay low. I set mine up to be at full extension at ride height. I want to be able to hang a tire and limit droop. But I'm not willing to sacrifice COG for more uptravel, so I think 4" is the sweet spot unless you run a high body.
I'm interested in a dual rate setup, but need to find out more about what's available. I'll chime back in here or pm you if I see something that looks promising.

[overland_yj]

well i am currently building a custom buggy with the worminator axles and the rc4wd tranny. first i used an r2dig and then the 1:1 tranny.

i am sorry to say i have to agree with "zoojunkie" (just because i am stuborn and must prove things to myself) i hate also to say that as far as i am concerned these axles and their tranny counterpart are no good... for my application.

i tried everything. smaller pinion, larger pinion, regular r2dig tranny, 1:1 tranny, 25:1 and 40:1 gears in the axles, brushless 18.5, brushless 13.5, brushed 55....on and on and on. i just cant get this to an acceptable level of performance. the axle/tranny combo is incredibly loud. i can get lots of speed out of it and then no torque at all or lots of torque then no speed (and i mean NO speed). i cant find the sweet spot, the happy medium between torque and speed needed for a crawler.

if anyone has some input or advice (besides sell it all, because that is already in my mind) then please feel free to offer it up here. what have you done that works? i already know what doesnt work

[shelljeep]

I can't give you any advice other then wait a few days for my results.
I'm hoping to have my worminators here by this weekend, and I'll be installing them in the LCC asap.
If I can make the 25:1 LCC axles work, than the 25:1 Worminators should perform the same. If I can't, I'll look for drag somewhere.
Do your pinions spin freely by hand?

[overland_yj]

Originally Posted by shelljeep

I can't give you any advice other then wait a few days for my results.
I'm hoping to have my worminators here by this weekend, and I'll be installing them in the LCC asap.
If I can make the 25:1 LCC axles work, than the 25:1 Worminators should perform the same. If I can't, I'll look for drag somewhere.
Do your pinions spin freely by hand?

yes, the pinions in all (3) motors i have tried spin freely by hand. 2 of them are brand new out of the box.

drag is not an issue, i can get the thing to fly across the ground.....until a 1/2 rock gets in the way and then it can even (crawl) over that and the motors are getting super hot. or i an get so much torque out of it the thing will climb glass but it would take 3 hours to cross the garage floor.

good luck and keep us posted.

[shelljeep]

I meant the axle's pinion.
Can you spin it freely with your thumb and forefinger?

[overland_yj]

Originally Posted by shelljeep

I meant the axle's pinion.
Can you spin it freely with your thumb and forefinger?

the whole driveline spins fine by hand. that is not the issue. the issue is the gear ratio. let me know how it works for you.

[aconsola]

Originally Posted by zoojunkie

your LCC transmission will not help you, it's .87:1.

The lcc transmission with 25:1 worminator gears should be perfect, as the losi axles are also 25:1

The .87 you quoted is the internal gearbox ratio. You left off the pinion:spur ratio which is variable(on the pinion side at least, the "spur" is fixed at 46.)
With a 12T pinion you get a gearbox reduction of 3.33 and an overall final drive ratio of 83:1
Still doesn't fix the fact that 25 or 40:1 with a 1:1 gearbox is a poor choice. This thread kept me from getting a worminator setup as my first rig, I got an LCC instead.

[shelljeep]

Well, I got the axles in yesterday but not the 25:1, so it won't be an apples to apples comparison against the Losi stuff. It does give us an opportunity to test whether gearing placement in the drivetrain matters more than final drive ratio. 25:1 to 40:1 in the axles equals 13T to 20t on the pinion for the same final ratio.
I'm not sure how well it will work. These electric motors aren't the same as in the 1:1 world, where say, you install a Powerglide to replace your 700r4, you can make up the loss in gear reduction by changing the axle gears, thereby relieving strain from all parts upstream. These electric motors don't like overcoming excess resistance on the first revolution, which is what you are creating when moving from a 13T to a 20T pinion.
It could go either way, and I'm interested to find out.
I'll be going to the lhs today to pick up the metric hardware I need, and I think I have enough delrin rod left to make the links I need. I hope to get this done late late tonight.

[Sharkey]

your comparison to of a 700r4 vs a glide is flawed. the only reason people run glides is in a drag car, your rear end ratio needs to allow the car to go through the top end at its peak rpm. to make up for it having tall 1st gear you run a less efficient torque converter creating a higher stall point, this is what gets the car moving. imo drag racing is still no reason to run a glide, but thats a different argument.

the final drive ratio is the final drive ratio, it doesnt matter if some reductrion is in the tranny and some in the axles. the only thing to worry about is drivetrain efficiency, with a worm gear axle you will need to have a numerically higher final drive ratio to make up for its inefficiency.

[shelljeep]

I know exactly Jack about drag racing, and that's not what I was referring to.
Some rockcrawling teams use a glide becuase of it's small size, weight and power handling ability. When they do, they have to add gear reduction elsewhere to achieve the correct final ratio.

[shelljeep]

I'm sorry guys. I'm not going to be able to put these axles under my rig tonight. They are missing 3 outer bearings, and the rear worms are worn badly. I have to wait until I get the rest of the parts.

[rcjackson0926]

Originally Posted by shelljeep

I'm sorry guys. I'm not going to be able to put these axles under my rig tonight. They are missing 3 outer bearings, and the rear worms are worn badly. I have to wait until I get the rest of the parts.

Please post some pics, I am curious to see your rig. I am also very curious to see how the worminator axles perform with the LCC. I have been having problem with my LCC worm gears and was hoping the worminator ones would hold up better.