[Experiment] "Painted-On" traction tires

[jtlan]

Some time ago this thread appeared, talking about a substance called "Bullfrog SNOT":

I came across this thing called Bullfrog Snot. Has anyone tried it on LEGO trains? It looks like it might do the trick to get this thing running, but wanted to see if anyone had any experience with it before I drop $20-30 on this small jar of goop.

After some initial confusion (is this some sort of new building technique?), I learned it was some sort of substance model railroaders could "paint" onto their wheels to add traction. I was pretty sure that it would just be worse than an actual traction tire, and forum posts reviewing the substance seemed to agree with me. The train wheels Lego makes both feature a groove for traction tires already anyway.

However, I had been considering a couple things I wanted to model where the correct wheel size is closer to a Big Ben Bricks medium wheel. I didn't trust myself to cut a groove into the wheels without access to proper machine tools, so I thought I'd try the "painted on" traction tires. One key issue, however:

I'm kind of a cheapskate, and didn't want to spend $25 on a tiny container of stuff to find out how well it worked. Furthermore, if it did work, and I posted about it, forum members who aren't from the only country to put men on the moon might have difficulty accessing the substance (although Tenderlok seems to have managed somehow). Time to find a substitute. Whatever I found needed to have the following properties:

1. Increase friction (adds traction).
   
2. Can be applied in a uniform layer.
   
3. Transparent, so it doesn't affect the appearance of the wheel it's applied to.
   

What has these properties, and is readily available?

Urethane caulk from a hardware store! However, caulk is far too thick to apply evenly in a thin layer. The packaging bears the words "easy soap and water clean up"; I took this to mean that I could thin it by adding a small amount of water:

I then used a small brush to apply this onto a clean spinning wheel to get an even coating:

I left the wheel spinning for about half an hour for the thinned caulk to dry. Here's what it looked like afterwards:

I built a small test vehicle and ran it on a figure-eight for about half an hour (so as to test it going around turns both ways). This was the result:

I'd worry about something tacky picking up every piece of dust on the track.

legoman666 is remarkably prescient... Pressing down on the test vehicle suggested that the painted-on tire had a bit less traction than an actual traction tire, but traction seemed to remain reasonable after a half hour of running.

I wanted a more thorough test though, so Commander Wolf installed the modified wheels on his QJ and had it pull some long cars for most of a BayLUG meeting. The result:

This stress-testing caused the tires to wear off. I'm not sure if that's a property of the substance (did I thin it too much?), or perhaps the underlying surface being too smooth for the caulk to adhere well. More testing is in order...

Edited July 19, 2016 by jtlan

[M_slug357]

I too need moar traction for my trains!!

I recently found a setup that allows me to lathe bbb wheels with a flat-head screwdriver. It takes a while and makes a mess, but the results are good enough to fit lego's own traction tires on. The one things that I've noticed about the traction tires is that they sit inside the rails instead on top of them, which leads to longer wheel assemblies 'choking up' in standard R40 curves and switches. I haven't had a chance to acquire some of that Bullfrog Snot stuff, but I'm kinda thinking it might be better (at least for myself) to lathe a few drivers down so that they'd be able to fit an O-guage traction tire. But most of the engine's I've made have done well enough despite this.

Your thoughts?

[jtlan]

I recently found a setup that allows me to lathe bbb wheels with a flat-head screwdriver.

The correct verb there is "turn" ;) Confusing, I know.

I haven't had a chance to acquire some of that Bullfrog Snot stuff, but I'm kinda thinking it might be better (at least for myself) to lathe a few drivers down so that they'd be able to fit an O-guage traction tire.

That would be my preferred solution, and I could probably pick the right size of O-ring from McMaster-Carr for a given wheel/groove, but the issue is that I don't trust myself to turn the groove into wheels consistently without destroying them (it's not clear to me that the BBB medium mold would support a deep enough groove). I have a mini-lathe of sorts in storage but I don't trust its accuracy.

[M_slug357]

That would be my preferred solution, and I could probably pick the right size of O-ring from McMaster-Carr for a given wheel/groove, but the issue is that I don't trust myself to turn the groove into wheels consistently without destroying them (it's not clear to me that the BBB medium mold would support a deep enough groove). I have a mini-lathe of sorts in storage but I don't trust its accuracy.

Trust me, if I can do it, you can too!

I sometimes feel like I have the shakiest hands in the west when it comes to building stuff... and then the first wheel I tried to "turn" did not want to cooperate... I really messed up. But, all the ones after I was able to do 90-95% consistently in terms of depth and straightness. So, as long as you have at least one volunteer/test wheel... you should be fine. I used an xL motor directly linked to the wheels being turned, which might be why it took so long for each wheel. The upside is that you don't have to wait even longer for it to dry properly. I'm wondering if some sort of chisel-type tool would be faster, and even more accurate than the screwdriver I used? but that also means moar money on tools so...

In the long run, the stuff that you were using as well as the Snot, seems like they might cause more problems/cleanup over time. The eventual (everything's eventual) rundown of the adhered substances could leave deposits on the track, which is disastrous for 9V-PF hybrid layouts. But then regular traction tires pick up and drop off sediment too...

[coaster]

I'd suggest the o-ring route from McMaster. Go with the 1mm wide Buna-N o-ring. Cut the groove about 3/64" wide and 1/32" deep. I don't have any BBB wheels, but I can't imagine they would go with a wall smaller than that. That should give you a nice groove to work with. As mentioned before, I'd put the groove on the riding face rather than against the flange to ensure traction on curves.

Also, would be interested in comparing round vs. square profile in this application.

[jtlan]

I'd suggest the o-ring route from McMaster. Go with the 1mm wide Buna-N o-ring. Cut the groove about 3/64" wide and 1/32" deep. I don't have any BBB wheels, but I can't imagine they would go with a wall smaller than that. That should give you a nice groove to work with. As mentioned before, I'd put the groove on the riding face rather than against the flange to ensure traction on curves.

Also, would be interested in comparing round vs. square profile in this application.

I currently do use McMaster O-rings on my official Lego "L" size wheels, but I believe I chose a ring with too small an inner diameter. That doesn't seem to affect the traction although I do see some small marks on them after many months. Primary advantage over the Lego traction bands is that they blend in on black wheels.

I suspect round profile and square profile will perform similarly in pulling power, and so round would probably just be better because it's easier to seat evenly. Time to dust off my copy of Mechanical Engineering Design and find some properly-sized O-rings...

[Lego Dino 500]

I'd suggest the o-ring route from McMaster. Go with the 1mm wide Buna-N o-ring. Cut the groove about 3/64" wide and 1/32" deep. I don't have any BBB wheels, but I can't imagine they would go with a wall smaller than that. That should give you a nice groove to work with. As mentioned before, I'd put the groove on the riding face rather than against the flange to ensure traction on curves.

Also, would be interested in comparing round vs. square profile in this application.

I need to get some BBB wheels and a lathe to try this out. Actually out of curiosity; Has anyone tried building a functional machining lathe from lego?

[ProvenceTristram]

There are some goop products advertised in Model Railroader for this exact same thing, albeit on HO locomotives. No idea if it works, but clearly this is a good idea that others have embraced.

[jtlan]

I need to get some BBB wheels and a lathe to try this out. Actually out of curiosity; Has anyone tried building a functional machining lathe from lego?

I think I saw one but it was cutting foam, which is super messy. The main issue is that ABS is not particularly suited for cutting anything except maybe soft wax, so the tool would have to be made out of something else.

[M_slug357]

I'd recommend that the cutting tool be metal, or maybe a teflon-coated something?

If I have the time, I'll try to come up with a brick-built rig of some sort that would allow for a constant, even pressure on the blade & groove...