Looking for friction

[kineteks]

...got my "kit" yesterday, I really like the layout and though the wheels seem a little Mickey-Mouse the whole package looks pretty good. I'm hopeful. So, with the motor & axle temp issues a bunch of guys are having in mind I decided to go looking for every source of friction I could find and see what I could do about each one. Both axles and the tranny on my kit seemed pretty smooth but not particularly free. After completely disassembling the truck I found a couple of things. I couldn't really evaluate the worm gears with the uber-sticky factory grease on there (one axle had gobs of grease, the other very little) so I thought I'd clean it off. Acetone & alcohol didn't do much but Simple Green did the trick, I have an ultrasonic cleaner so about 10 minutes in there and the gears and housings were pristine. Re-assembling and checking out the worms dry had both feeling pretty good, one slightly rougher than the other and both seeming like they'd benefit from some break-in. I couldn’t feel any lash between the gears at all so they’re definitely not set loose! All of my axle bearings have quite a bit of drag, I'm going to clean them out and lube them with something a little lighter. I'll probably still use a high pressure grease on the worm pinion bearing as they see a lot of thrust load, maybe a black moly grease. My worm spool had 2 shims per side too, when I took out 1 per side there was a little more slop than I'd like, this would have been tough to see if there was still some grease in there. I'm going to figure out how to get or make some thinner shims so I can set this up just right. For the worm itself I've got a couple of different greases to try. I'm going to start with Gear Jelly, 'cause I use it in my Berg and Clod axles and think it's neat but also have some synthetic cam/motor break-in lube that's thinner than the factory grease but made for high pressure contact. I’ve also got some stupid-sticky marine cable grease if the others don’t work. I don't know if you have to have a really thick grease to keep it on the gears or not... I'll know soon I guess. Like I said the tranny feels smooth but not too free either. I’m going to do the same thing with the bearings, clean ‘em out and re-oil with something more slippery. I may also pull the seals on the internal bearings if they have a lot of drag. I tried removing the DIG shift forks to see if they were contributing to the tranny drag and they didn’t seem to be… but while I was assembling and disassembling the tranny I noticed that the drag increased when I tightened up the main trans case. On my tranny the DIG/output shaft assembly is in a slight bind with the tranny is snugged-up. I’m going to take a little material off the A3183 spacer that goes between the DIG plate/outdrive bearings to get rid of that bind. I’m also wondering if some sort of TiN, TiCN or TiAlN coating (like on end mills & shock shafts) on the worms would make a significant difference in friction reduction, I haven’t found a place that’ll do small/prototype runs in a quick web search, but I’m going to look into this a little deeper. I’ll update this when I find out more….

[grouser]

sounds good we will ifgure out this I'm sure,,,
one point on the choice of grease,,,
do we need to be looking at grease that is "plastic freindly",,,I have heard that not ALL grease is compatable with plastic parts,,,any thought on this?

[kineteks]

I think most synthetics are OK with plastic but that's a generalization based on my experience with a number of different lubes. You should always test I guess. I'm guessing the axle housings are a nylon composite and nylon is usually OK with most chemicals... I'm no expert though.

My gut feeling is that most of these "improvements" even something like a TiN coating on the worms, will not make a huge difference and that the frictional characteristics of worm gears, especially when driven at relatively high speeds will be difficult to overcome. My plan here is once everything is as free as can be reasonably achieved to see whether it makes enough of a difference that a brushed motor is an option and failing that to see whether run time on the appropriately sized battery is sufficient to make this a viable crawler for non-comp use.

[kineteks]

I just found this and it may be a reason to look at TiN or other lubricious coatings...
This is from "The Ins and Outs of Worm Gears" the full article can be found at...
http://www.oilanalysis.com/article_d...articleid=1080

There is one particularly glaring reason why one would not choose a worm gear over a standard gear: lubrication. The movement between the worm and the wheel gear faces is entirely sliding. There is no rolling component to the tooth contact or interaction. This makes them relatively difficult to lubricate. The lubricants required are usually very high viscosity ….
Lubrication
The main problem with a worm gear is how it transfers power. It is a boon and a curse at the same time. The spiral motion allows huge amounts of reduction in a comparatively small amount of space for what is required if a standard helical gear were used. This spiral motion also causes an incredibly problematic condition to be the primary mode of power transfer. This is commonly known as sliding friction or sliding wear.
With a typical gear set the power is transferred at the peak load point on the tooth (known as the apex or pitchline), at least in a rolling wear condition. Sliding occurs on either side of the apex, but the velocity is relatively low.
With a worm gear, sliding motion is the only transfer of power. As the worm slides across the tooth of the wheel, it slowly rubs off the lubricant film, until there is no lubricant film left, and as a result, the worm rubs at the metal of the wheel in a boundary lubrication regime. When the worm surface leaves the wheel surface, it picks up more lubricant, and starts the process over again on the next revolution.

[grouser]

interesting post ,,,thanks
If I had my choice I would seal the axle and put a differencal oil in it,,,something that has ALOT of stickie to it (Red Line )

[mspohn]

Just opened mine when I got home, Turning the drive shafts seems smooth, not much drag, but no resistance yet. I have the Losi 17 brushless system to drop in and batteries on order. will have to see when they come.

[Kamikaze]

They will turn smooth and easy till you place a load on them.

[celsiusprime]

True that. I'm using a Novak Goat 18.5 in my truck, and I should have plenty of torque because of it. But if I pull the truck up to a vertical wall, it won't hardly budge the front wheels up it. This truck torques out really easily. Anybody know why? Is this one of the standard trawbacks of a worm drive?

[renoirbud]

Some of the instruments I work with have screw feed hoists and I have had a very hard time finding a lube for them. I found this;

http://www.genie-garage-opener.com/lubmulgreas1.html

And have been thrilled with the results.

• Advantages
• Low torque start-up capability
• Corrosion and oxidation resistant
• Long lasting film strength over a wide temperature range
• Outstanding aniline point of base oil offers excellent compatibility with exotic metals, plastics and rubber materials

[Dark8ngel]

I use the Molub-Alloy that we/I use here in the Taconite/Ore Mine. A very harsh and demading enviroment on grease. Check out the "axel grease exp. and temps" thread for the info.

[4x4transam]

I run automotive black high impact grease in my axles and a few drops of Lucas Oil additive in the trans, runs very smotth not much drag at all, and it way more quiet now too, no overheating issues never got motor or ESC over 115

Novak Goat system
18t Pinion
2000 7.4 lipo
1 hour run time
DX3R

[on stolen rocks]

what about a self lubracating plastic like delron or teflon coating on an aluminum gear