Joining the Anti-Slinky Fray

I've been reading and thinking about comments I've found on the web regarding MTL cars and the "slinky effect." So, being an engineer, I did some quick analysis and posted what I noted in this blog:

www.zcentralstation.com/index.php/my-z/test-my-blog/entry/avoiding-the-slinky-effect

I'm building a layout, on which I'll test my theses, but if anyone has comments/criticisms, I'd love to hear them. Hoping it's helpful...

ZRailFan, You are hardly the first engineer to attempt to solve this issue in the past decades. Sadly, the solution doesn't seem to lie in math or theories. One way I solved this dilemma was with the simple 'scientific method' approach. Using magnifying goggles and tweezers I carefully attached one very small piece of electrical tape to the inside of each knuckle or jaw, correct size found after many tries. Very tedious and time consuming but effective.

An interesting thing I found out was that all MTL couplers were not created equally! Some times a really tiny second tape had to be attached to the other side of the jaw, the side of the jaw facing the next car's coupler.

Final thought. Keep on trying to figure out a solution this is looong overdue, probably because of tooling costs.
Also, I never used my MTL couplers in magnetic uncoupling mode. No time or patience. Keep up the good work. Jim

Yep! I'm in ! I just did a set of eight cars they are 3D printing and designed them so I could add weight to each car, I ran all eight cars with one of my CSX GP-38-2's and got the derailment effect on switches and curves. Not all but just the center car in the consist So then I added weight to each car and did another run and got the Slinky effect. I don't know exactly how much weight I added since I didn't have the weight or scale so I order one of those in this post. So I guess I have to add more weight! I tried to run the cars up a 2% grade and it was just to much for the little GP-38-2. SO if I add more weight to each car I think I will need to run a double header to make the incline! What do you think? I bought the weight at hobby lobby they are half round weights use for pinecars. It said that the net weight 2 oz (56.6 g) it contains four strips with six pieces in each strip I'm using three piece for each car,

I use BBs for weight. They are cheap, stack nicely, and you can get them at Wal Mart or your favorite gun shop. Make up a train, add one or two balls to each car, and then run it around for awhile until you find the magic count for each car. Don't forget to test backing on to a siding. Paint your balls flat black and then a drop or two of white glue to hold them in place. I like the metal wheels but I find the lower resistance adds to the slinky effect.

! I just did a set of eight cars they are 3D printing and designed them so I could add weight to each car

3D printed...cool. That is something I'll have to try someday. Where did you get your design, or did you draw it up yourself?

I'd check the weights. It wouldn't take too much weight to be too heavy, and my table is just an estimate using scale as a guide. I should be getting some track today in the mail, so I can try some things out as well (no local shop carries Z, so everything is mail order). But I'd love to know what they weight so we can zero in on an ideal weight. It may be there isn't a perfect solution, although I also wonder about playing with the springs (harder to do than adding and verifying weight).

Hopefully you'll find the cars are a touch heavy, but if not we are limited by the tiny motors. The body scales well, but not the horsepower. But then I also see many consists being pulled by multiple engines, so that's not so un-prototypical. Are you running DCC and can tailor the power?

You are hardly the first engineer to attempt to solve this issue in the past decades.

I'm sure not. Just hoping to understand what other folks are seeing and have tried. My thought was to apply the logic used by the existing NMRA standards, but it's just an estimate at the moment. It may be this isn't the solution, or is a partial solution. It's at least something I've not yet come across in my readings.

I like the metal wheels but I find the lower resistance adds to the slinky effect.

Ah! Could be so. Once I get some track laid I'll experiment.

I played with this a while back after listening to people complain about the effect in Medford in 2010. Assuming we are stuck with existing hardware, basically the problem is that friction drag is less than the car's momentum. Because the friction scales linearly with weight but inversely to the contact area the drag drops as you reduce scale. Changing to metal wheels makes the problem worst because the metal wheels result in lower friction in the wheel sockets and between wheels and track..
To increase drag, I've thought about flattening the needle point of the wheel sets, and as much as I like metal wheels, staying with plastic. The other thing to try is adding modified piece of rolling stock to the end of the train. The MTL dummy F7s seem to fix the problem for me. I'm thinking the wheel wipers I'm adding to a boxcar for a FRED will do the same.

These are My own design requested by a friend. I had to do the car in two pieces so I could cover the weights. I think this is a good thing at least trying to find something that will work! then get rid of the slinky Fray. I will have to wait till I get my scales in a couple of days to check the weight of the car with out weight and the car with weights. I have the decals already done just need to get them running right. I'm using the Roller bearing MTL truck. I will have to get a couple set of metal wheels to help out with your findings. I have done several 3D printed cars. The flat cars will be easy to add weight by placing a load on the car with weights. But the others will be a challenge. All the Engine have there own weights from the chassis. I think this will be a good post! I was thinking if the set of weights are 2oz (56.6g) and divide that by the number of pieces in the pack that should give me the weight of each piece or close to it. So there are four bars 3"long each bar is divided in to 6 pieces if broken. Each piece 1/2" long. So I divided 56.6 by 24 pieces and come up with about 2.4 g per piece rounded off. I use three pieces on each car. that would give me 7.2 g added per car. I don't know the car weight or the set of trucks to get total weight! But as I said before I did order one of the scales and should have it in a couple of days! Question I have one MTL 50ft flat car running with this group of cars It has a six wheeled truck with MTL wheels but when it runs it sounds just like the real wheels on a train it squeals and seems to drag. I have it running as the last car in the consist. I have checked the wheels and they turn good I even put a little oil and it didn't make a difference at all. What else can I try?

Changing to metal wheels makes the problem worst because the metal wheels result in lower friction in the wheel sockets and between wheels and track.

Interesting. I would have thought crud on the tracks would catch and slow the wheel, causing it to rotate a bit more slowly and lag. Then as the locomotive force pulled the wheel horizontally, it would pop back into line. Kind of like stepping on a wad of chewed gum.

But what you're saying is the metal wheels make it glide as if on ice, so the spring tension is exacerbated. I can see that happening, if the spring tension is great enough, as it appears that it is. In that case what you've suggested is to increase the rolling resistance to exceed the spring tension force. Makes sense.

I wonder if I can't also reduce...well...dampen the spring motion. After all, that's the cause of the issue. Left alone, the spring extends and retracts while the car is moving, still probably due to effects further down the line or due to it's own wheel set dynamics. I have an idea I'll test out when I get some track laid and power applied to the rails.

These are My own design requested by a friend.

Wow! That is soooo cool. If we ever meet, beer's on me. I have a thousand questions. Having recently rejoined the hobby, I'm still thinking like it was 30 years ago. It never occurred to me to buy a 3D printer. I saw your pics, and I'm completely stunned. I'm a huge tank car fan (no idea why), and wanted to model some sort of drilling/refining scene. With a 3D printer maybe I can. Loved your oil storage tank. Don't wanna go off topic here to that degree, but I might send a PM and ask your opinion on a printer I found on Amazon. Looks most excellent.

Question I have one MTL 50ft flat car running with this group of cars It has a six wheeled truck with MTL wheels but when it runs it sounds just like the real wheels on a train it squeals and seems to drag. I have it running as the last car in the consist. I have checked the wheels and they turn good I even put a little oil and it didn't make a difference at all. What else can I try?

Ooh, good one. I'm no expert, that's for sure, and without actually seeing it, it could be hard to pinpoint exactly.

But sound means vibration, and vibration can come from many sources, so as a mental experiment I try to think of all of the sources. Rubbing, dragging, scraping...stuff like that. When rolling, for the moment assuming no issues between the track and wheel, it can only be coming from the bearing box (well, simulated bearing box, where the wheel set meets the side of the truck) or perhaps a wheel is touching the underside of the car. Even if it seems to roll, is there a tab or burr nearby? Are the points of the axles well-formed? Centered?

Note if a wheel is touching the underside of the car, you'll have to look closely for that with the car in-situ...you'd probably never notice it by lifting the car off the tracks. Does the car lean at all when running, either on straight or curved track?

I'm not sure what oil you used, but if liquid I'd, myself, clean that off and go with dry graphite. At least that's what I've found works better for plastic to plastic friction reduction. There are lithium greases that work well too.

If none of that, is the issue seen mostly on curves? (Returning to track/wheel interface...) A six wheel truck is like a passenger truck, and "back in the day" those used to be temperamental on curves that were tight or too tight. I don't know what the recommended minimum radius is for Z, but in HO you'd not like to see anything less than a good 32", and even that is on the tight side. Doing the math, that works out to be close to 12.5" in Z.

Are the wheels in spec? We don't have nice NMRA gauges like in the larger scales, but if the flanges are even a fraction of a hair too far apart, they'll scrape the rail. The sizes we're talking about are so small I'm not sure an eye could tell, but a nice Vernier caliper could tell us. Compare the flange to flange distance with the six wheel truck with another set of wheels you trust... This is a nice caliper, and on sale too.

www.harborfreight.com/6-inch-digital-caliper-47257.html

Just some thoughts...hopefully helpful.

I'm interested in how you are doing the FRED. I have a DDC decoder that I let SOME OF THE SMOKE out of. I thought I could mount it in a box car and use the lighting functions to drive the FRED. Where do you get the wheel wipers or does someone make a truck with pickups?
Thanks
Tom

t.edmunds wrote: I'm interested in how you are doing the FRED. I have a DDC decoder that I let SOME OF THE SMOKE out of. I thought I could mount it in a box car and use the lighting functions to drive the FRED. Where do you get the wheel wipers or does someone make a truck with pickups?
Thanks
Tom

You're possibly over-thinking the project. Evan Designs makes a battery-powered unit: www.modeltrainsoftware.com/fred.html that I looked at in Portland last year, which IMHO is too big for Z scale. But they also make a slow flasher circuit with a Pico LED that I bought. The circuit is designed for 7-22V and works with DCC and the Rokuhan lighting function. The FRED I'm modeling looks like a WWII walkie-talkie that sits in the coupler and the Pico LED is just the right size.

I'm using axle wipers from Richmond Controls in TX. He's a small operation but I see that Monster Z is selling them. For wheel wipers try: www.sbs4dcc.com/zscalewheelaxlewipers.html
He also produces MTL trucks with the wipers installed.

Mark

Still waiting for the scales to arrive. have four more piece to add, these are also 3D printed, gondola's use MTL brown colored roller bearing trucks have add these to the consist in question for the slinky affect! Haven't done anything yet!

This is a nice caliper, and on sale too.
www.harborfreight.com/6-inch-digital-caliper-47257.html

Went and picked up the 6" Digital Calipers great price for a metal Caliper! Does measurements in inches and mm. also has the depth gauge also! extra battery came with it, and case. Thanks for letting me know! No scales today have to check out where it is! it should have gotten it by now! Here is another 3D printed Car I need to add to the slinky Fray.

This is a nice caliper, and on sale too.
www.harborfreight.com/6-inch-digital-caliper-47257.html

Yep...I think that's the same one I mentioned. I use it when doing some work on my cars (restoration), but I've since brought it in from the shop to use for laying some track. Starting a layout and wanna hand-lay all of the track. I have the NZT clearance gauge set, but for turnout work I need other tools.

I'm loving the 3D work you're doing, would love to learn more.

I think you might want to talk to john here he has been doing the switches he does a great job. I haven't done any more with the slinky fray yet still waiting for the scale. I see that some use Bee bee's. I haven't tried that but have tried adding cars to the end but since my 3D printed car are light, the heavier car pulled them off on the curves and that wasn't fun. So I have to weight maybe once I get them all to weight the same the slinky effect will disappear. that even happens at a very slow speed one catch and they get pulled off the track!

Well got the scale today! Nice scale for the price professional looking piece. test 1 cars with out weights.




Now! with weights

Oh yeah...that should be much better. Whatever a "good" weight is, 0.06 ounces has got to be too light. Be interested to see if they run (behave) better as well...

I was pleased with the scale too...I like the nice little protective cover. Great idea to keep such a small, sensitive measurement tool safe.

Those are some fine-looking cars. Nicely done.

I'll tell you one thing those cars without weight runs good as long as there no problems with the track my switches have been the derailment problem. But there Markln. I need to get my newer track up it not Rokuhan but MTL track I will be using. Good way to check track!