project 3905 e maxx

hi all...
yes redshift thats the stuff, really sticky designed to stay until oil pressure is up.
i think your gears would have worn down in a year to the point they are weak at the tooth, i had my nylon ones for around 6 years till i switched to brushless, they were well worn tho.
i run offroad mostly, have a rear difflock (spool) using the maxx paddles and try to climb the biggest mounds of mud i can find, like formula one offroad.
i think this put a hell of alot of strain on the transmission and is the reason the nylon cogs fail so quickly.
rivermaxx, nice speed pass, 80 mph upside down i bet that put a few scratches in your shell. my truck dont go that fast its geared down to around 40 mph top speed which also puts more strain on the trans.
not shure how much my truck weighs, have to get the scales out and weigh it.
you lost me on the titanium gears? what? where? see ya all....
just looked up on ti gears and apparently there not worth it. might as well use steel
http://www.eng-tips.com/viewthread.c...=252337&page=1
found much more evidence than this but thought you may like a read yourself...

[redshift]

Well not to second guess you, but it seems like engine assy lube is overkill. I only bring this up because you were talking about rotating mass. How would rotating mass be an issue if you're running tar in your gearbox?

The failure I had was purely shifting under too much throttle, the gears are all flawless otherwise. I would have taken pics but the truck is back together. The nylon gears all had a nice square apex, and NO signs of wear. I know the original Maxxes ran the trans dry, which makes for a powdery mess the first time it's split. But it was greased for a few years, then I switched to STP about a year ago. The only other time the trans had to come apart was when I sheared the rollpin on the input shaft. Did a solid pin as well, with about a .002" taper. Banged them in with a railroad mallet and green loctited.

I also use a spool in mine, and that puts quite a bit more stress on things. The trans has been the least of my worries, I have destroyed 2 MIP bones and 3 of my own drives, one steel and two titanium, all with plastic lower gears... mine weighs 15 pounds now with a rubber front bumper, and goes like a 10 pound truck. The real weak point is the damned rear pinion. I always curse at them for putting the two little 6x12 bearings so close together. If they'd have extended the distance in between by even 8 or 10 mm there would be significantly fewer bearing and mesh problems. Even with an alloy diff case, there is just too much rock in the pinion axis, and it quickly eats itself.

That's one thing STP can't cure....

[redshift]

Good bit of info there on the use of titanium for gears too

[Rivermaxx]

You really think going 40 mph puts more stress on a tranny than gearing it to go 80mph? Yea that 80 mph pass upside down I hit a road reflector and it sent the truck flipping. Did you see the 75mph wheely? If any thing puts alot of stress on a tranny that should of done it.
I haven't tried those ti gears out yet and I only have about $40 invested in them (got them off ebay). I figured I would try them out when my others failed but havent come to that point yet. Your steel gears will most likely wear the same as those titaniums gears if they are not case hardened unless they have constant lube to prevent failure. Any thin light weight synthetic oil would probably be best. The thick sticky stuff will probably just slow you down and burn up your esc because of the trans acting like a hydralic pump.The biggest problem with those stock trannys is the shifting causes failures. Gorillamaxx saw this and adressed it with the single speed G1 conversion which pretty much make the trans bullet proof. With brushless power you dont need the 1st gear and its not really low enough to do real crawling anyhow. My other g-4maxx creeps pretty good while in second with the lower geared 1/8 scale diffs and 3905 revo tranny but I built it as a racer not a crawler.

These are my custom titanium gears( I believe only 5 sets ever made) with one UE gear(top left) that is in use now. Quite a bit weight difference between those and steel. Aluminum is the worst material to use for gears as you found out but the ultramaxx gears are made from a harder 7075 billet aluminum with a brass alloy idler and last forever with proper maintenence.


As far as the diffs failing do yourself a favor and put some 1/8 scale diffs in(like UE or FLM) and never look back. I broke stock diffs with nitro power all the time.

hi all...sorry guys i did not make myself clear, i have not just poured this thick lube in the box, i have just coated the cogs on all meeting faces with a few drops of the lube as thinner oil will not stay in the box.

rivermaxx, i agree with the rear pinion weakness but then again this truck is not designed for 5-6hp, the weakness is because the rear crown wheel and pinion are not cut correctly, if you magnify the rear pinion you will see the contact marks are on the outside edge only so the tourqe is taken by just a few mm of tooth, i am still using my original front pinion but my rear has been changed out for the newer 3906 due to failure. i weighed my truck and its 11.3lb not too bad seeing as its extended by 40mm . and yer there is alot of free play in the bearing even when they are new.

redshift, yes when you reduce the gearing you amplify the torque, thats how come i smash cogs and you dont, the problem i have is with the smaller 20 tooth cog. but seeing as i was splashing out on gear cutters, for another £40.00 i could make the 31 and 36 tooth cogs from steel as well. i dont crawl with my truck as id loose the will to live at that speed but i climb the biggest hill i can find and my truck is geared down with the spur so 1st gear is good to climb. those ti gears look wicked tho, i allways dip the throttle when i change gear to prevent damage, it tells you to do that in the manual.

sum pics of my latest venture to margate beach, bent a rear drive shaft and poped a front shock




bye all...

redshift...hows the mutant going these dayz? ment to ask, any new developments? just been watching some of your videos all you need now is some sort of self-righting thingy-ma-bob, maybe a hydrualic ram on the top hinge robot warz style, so it flips the truck up in the air and onto the wheels haha. oh and do you shim your rear crown wheel over in the diff? that will make it last a bit longer

[redshift]

I was gonna get back to this thread earlier... sorry!

Ok yeah, same deal with the oil treatment, very small amounts. I just recommend that because it's available anywhere, and cheap.

You are quite correct about the bad mesh on the Traxxas ring/pinion. And this has still not been addressed. Same goes for the spiders. It's a shame they refuse to make improvements where they KNOW they need to. But then they don't make their money from RTR stuff do they... As far as shimming the rear, I have, but it seems to make no difference. Maybe amounts to minutes lol. So I just consider those expendable. I've considered going with an all metal trans, but it hasn't been an issue. I know about letting off when you shift.... just not that one time I don't really do much crawling, but first is just perfect for some things (like when you blow 2nd). As for the Mutation, that was started before I really knew about brushless at all. I didn't anticipate what it would become, past brushed. And the timing with brushless worked great for me as I was able to do a reliable setup and not go thru all the experimentation with different power systems. I say reliable electrically

I've considered going with the 1/8 diffs, but there are a few things that would pretty much necessitate a full redesign, so it may or may not happen.
But who else can say they've gotten 4 years of fun from the same RC?

And yeah BattleBots/Robot Wars did inspire me somewhat, and a self-righting device would be the cats ass!

There is a lot I'd like to do with it, but if I did I'm afraid there wouldn't be enough 3906 left to call it such. The 'train was adequate for brushed power (barely) with some CVDs, and I did go thru a few sets of plastic idlers, but really I had no idea what MILD brushless power had in store for it.

Your machine work looks very good, and I am extra impressed you're using conventional machines- I have a CNC allergy. They make unbelievable stuff, and I work around them, but I am oldschool. And there are still lots of things that cannot be made by CNC. I let the pros do the programming, I'll have the part made before they have their program imported :)

I have a diverse background, but no experience in gearcutting. Nice to have a few who are experts on such things, besides the Monster himself of course!

Looks like a good playground there too

hi all/redshift...will look into a splash fed box when i get my alloy casing , sounds like the best idea..
so what wheel shafts do you use on your maxx? mip's

i can see why you dont want to change over to bigger diffs, shame tho as it will turn out much better than before.. i found this with my work.. if you get it wrong you will get it right next time . i can say ive had several years of good running with my e maxx and its just getting better now brushless is available.

thanks for compliments on the work, when i first machined a cog the calculations looked confusing and i was not really sure what i was doing was right, like any job i suppose, now ive cut a few its easy. bearing in mind its just a copy job not a gear train from scratch. try it if you have the machinery, get the o.d right then its all down to cutting depth and correct indexing.

the beach is great.. they get a bullbozer down there and build up the sand to keep the water off the road when the wind gets strong in the winter. theres a quater mile streach of it see ya all...

[redshift]

You can read about my driveshaft woes here- http://www.rc-monster.com/forum/showthread.php?t=20677

But yes MIPs up front, and they are several years old. I actually avoid extreme sandy locations, so that's helped with longevity. If I do get it gritty I blast all the drives with solvent and re-oil in short order. They have to be replaced soon, might try replacing pins only, gage pin material has held up fantastically with the drives I've made.

All I have at home is an heirloom Atlas 612 lathe with a 3 jaw, but I have everything I need at work. I kind of doubt I'll ever need to dabble with gears, but I'm always looking for new info and ideas

hi redshift... ye interesting read, im not bothered by the sand as i make my own pins and barrels for the mip's- bit of silver steel then harden with a mapp gas torch and water. just have to strip and clean shafts after the run.

nice attempt at sum shafts tho, i made mine from 316 stainless, easy to machine and no rust . i made mine 1mm thicker at the shafts thinnest point so they are a smidge stronger and seem to resist bending better, putting a set on the back will be the real test as i still have my 5 years old mip's on the rear but the centre rear is stainless, i extended my truck by 40mm and had to make a shaft that fitted

gears can be cut on the lathe using a rotaytable (must have indexing plates too), but for you it would have to be a careful choice under the centre height of your machine then the table would have to be raised to correct centre height

ha ha that shaft is well bent in your photo, i thought i bent mine badly, problem i get is as the mip's are quite strong/brittle they tend to start splitting along there length in a helix type crack after i bend em straight a few times, i have not had this so far with the stainless ones and have straightened them a few times each, so far and all good.
see ya all...