Mamod Spring Belting. Any US Source?

Model Railroader General Discussion (Model Railroader)
1

G’day folks.

I recently tried to fight off the temptation to adopt yet another example of a unique locomotive. The New York Central T-3b won [:-^]

NYC_T3_Alco-side by Edmund, on Flickr

The seller made it clear that there was “trouble” with the spring couplings [his words] but I figured this to be just one more challenge for re-powering or adapting a better drive system.

Here’s a look at the overall arrangement:

NYC_T3_Alco-works by Edmund, on Flickr

On one end, away from the brushes, something seems to be interfering with the worm shaft in the truck gearcases. One of the spring belts is not as snug as the other on the brush-end.

NYC_T3_Alco_1 by Edmund, on Flickr

You can see the ends of the worms which engage the brass axle gears in this view:

NYC_T3_Alco by Edmund, on Flickr

The sheaves have knurling in the groove to improve grip. Replacing these spring belts with an O ring is out as I would have to cut the frame and gearcase. There is structural work in the way. The spring belts can be threaded through and around the worm shaft, then joined.

I discovered the spring belt was a somewhat common drive technique

2

What I can tell you as you have “The Knowledge” is to go ahead and roll your own using a piece of appropriately thin threaded rod of the right pitch (thread it from rod if there is trouble finding it ready made) using hardenable wire of some appropriate type – then annealing it again once worked and harden it to spring quality afterward… I would use a larger version of a watchmaker’s silver-sand bluing bed and carefully take it up to blue ‘temper’ after you have it to length with the hooks at the ends oriented right.

I think the Mamod belts are too ‘soft’ in their spring rate to be effective, particularly at slow speed against resistance: the locomotive will move in a series of jerks, like a Tempest with that idiot flexible driveshaft, as the belting tensions and springs back. A blued helical spring should still traverse the pulley even with the relatively long ‘non-springing’ coupling, but with much less tendency to stretch…

The alternative is to get a jewelry inline screw coupling, of the kind used for bangle bracelets, and key O-ring elastomer stock into it. This might be a little lumpy going over the pulley but perhaps acceptable. I’d also be interested to see if cutting a longer O-ring to size, using a dab of Pliobond or other adhesive RTV material between and over the ends inside a short sleeve of thin shrink tubing, and then shrinking it on would give you a custom installed belt – repeat the process on a new part of the belt any time you take it off for adjustment and then go to put it back…

3

Ed,

Was that the one that was on eBay recently? If it was I saw that and “briefly” toyed with idea of purchasing it. I’m glad I didn’t deny you the pleasure of researching how to repair it. [:D]

Tom

4

Thank you for your suggestions, Overmod. I’ll certainly consider these options but I’d really like to exhaust my “low-hanging fruit” options first. Perhaps the reason the bands are doubled is to overcome the “fluidity” of the spring drive?

Quite possibly the one, Tom. I frequently place items in my watch list. In the case of this T-3 the seller contacted me with “such a deal”! How could I refuse?

https://www.ebay.com/itm/HO-Brass-ALCO-Models-NYC-New-York-Central-Electric-T-3-RUNNING-ISSUES/283964084416?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m2749.l2649

Ebay doesn’t show the discounted selling price, apparently. I got about 20% off [:)]

While doing a little more digging I found this reference to a Varney drive:

Varney_drive by Edmund, on Flickr

Don’t ya’ love that three-speed stepped pulley? Wouldn’t that be a neat feature to have today? Locomotives with a three-speed transmission!

My friend Google found a source for 2mm spring belting right here in OHIO and they’re on sale!

https://www.ministeam.com/acatalog/Z82-Flexible-belts-in-500-mm-lengths-pack-of-5-pieces-WI_Z_82.html#SID=244

There were still some T-3s around when I was in Harmon back in the early 1970s but I don’t recall any of them under power.

Thanks, Ed

5

If you’re retaining the Mamod belts in the mechanism, you might consider operating on the ones you have a bit before spending to replace them, unless they have wonky soft or stretched-out sections in them. I believe you can bend up coil by coil and reform the ‘eye’ to shorten one that is a little stretched; once they are both bearing on the grooves in the pulley I don’t think it will matter if one’s a little tighter than the other. Be careful not to stretch out the eyes when hooking and unhooking the ends under tension!

6

THAT part of the operation takes the patience of Job. There’s only about 5/8" of free-end at the deck. I have to handle the spring with forceps. I’ll try again in the next day or so.

I would like to try the Mamod method where the one end is tapered and by counter twisting the ends they will “thread” into themselves.

In theory.

Cheers, Ed

7

If I were you, I’d make up a special tool, perhaps starting with a hemostat or fuel-line pliers: it would have a ~2mm semicircular recess in each jaw, to grip the spring circumferentially, with elastomer or something like it in the jaws for compliant grip. The hemostat tension would hold it both in position and alignment as you bring the free end down and hook it. I would also think about the idea of using something like small jump rings of different sizes and circular or oval cross-section to make an adjustable length at the connection between the two hook ends, perhaps with a little dab of silicone to hold it against inadvertent compression once assembled.

This is a bit easier when you have the belt out free and can wind it in reverse the number of times necessary to get it to ‘bite’ with the needed resistance to tension. You only have that luxury if you derail it from both pulleys while torquing up and it will be amusing in the extreme if you don’t have at least three tools comparable to the above: one to hold the ‘neutral’ end of the spring, probably the socket end; one to hold the other end below the taper to be secure against what will probably be serious unwinding torque, and another to take open-jaw wrench like ‘bites’ of turning in the available arc at the side of the frame, under control by strategic careful loosening of the turned-end holder. I do suspect that if you can formalize the tools and sequence of operation you may be onto something valuable concerning this sort of drive.

It also occurs to me that with some sort of offset springhook you might be able to push up on the tapered end from inside the coil ‘behind’ it, to s

8

Hey Ed,

Did you ever find a US source for the Mamod spring belts?

I purchased the same undecorated Alco Models T-3 back in November. It runs well but it arrived with one of the four spring drive belts broken.

NWSL is no longer selling their 1300-1/TCRT1300 kit because they lost their original supplier for the part. I have a saved search for it on eBay but no hits for it, as of yet.

I tried contacting the eBay seller from the UK about the 1.5mm Mamod drive belt bands but he hasn’t returned my PM. He supposedly doesn’t ship to the US but his eBay site states “May not ship to United States” (italics mine). I asked him if that meant he won’t…or it depends?

I also looked into a chain & sprocket drive from Micro-Mark. The chain looks like it will work but the sprocket would require dismantling/unsoldering the gear box enclosure to access the gear box drive shaft. The gear box is also small so it may o

9

Ed) Interesting topic in many ways.

First, Ive always been a bit perplexed by these ‘Mamod drives’ as you call them. Never heard that word before, though ‘spring drive’ must be the ‘in’ thing to call them. Its all I hear. I dont own, nor have ever owned one of them. Id be really suprised if that even worked!

Now i dont have exactly what your looking for, but I have in the past given thought that if I was to come across one of these, what would i do without having to cut, weld, bend, remake, explode, reassemble, blah blah blah.

Best idea I came up with was to take the springs off (since they thread on/off) and dip them in latex resin. Molding them such as to use the spring as ‘rebar’ (as in cement) and the latex as the flexible grip outter skin. It was my thought that when reassembled (threaded back on after good n dry) that the latex would illeviate any slippage, noise, etc etc., while retaining its springyness. For stretchyness just slice a few spots down the length of it. I still dont own one (spring drive that is), so you can guenny pig that idea if youd like.

This allows you to only need 2cents worth of latex, you already have the springs, and a mere 6 hours of set time. If it dont work… clean the springs and start over. Lastly, you already have the original clasping and sizes since your using original parts. Thats about as low hanging, cheap based and fruity as I can get.

(to take care of the length, id clip the stretched one, and after molding, leaving the very ends unlatexed, i’d intertwine the ends together instead of using the now removed clasps. Kinda like what Kadee springs do in the bottle before you seperate them. It would look like a continuous spring.)

Another new thing you learned me tonight - didnt ever know anyone made a three step pulley for model locos. Seen it billions of times on drill presses to lawn vee-hickles and the like, but not a model loco. Though,

10

Well, yes and no. I bought what I thought were going to be the right size but they turned out to be 2.0 mm diameter. The originals are 1.25 mm! Tiny by comparison. The 2 mm is just too big to wrap around the pulleys.

This is the place I bought them from:

https://www.ministeam.com/product/Mamod-Steam-Engine-Model-E51/Toy-Steam-Engine-Parts

NYC_Alco-T3-drive by Edmund, on Flickr

So I bought a second T-3 just to get a couple extra spring belts (it only had three good ones) and I did get the chassis running. It really isn’t too bad as far as smoothness and noise but the motor I have is drawing 1.25 amps at mid-speed and I’d like to get that down.

Like a dummy I gave away two spare motors I had [:'(][D)]

NYC_Alco-T3-motor-aft by Edmund, on Flickr

Those other motors would probably have the same high current draw, though.

NYC_Alco-T3-bottom by Edmund, on Flickr

So it is prophetic that this old thread came up again as I was just going to turn my attention to these T-3s. While searching for something completely unrelated I stumbled upon these:

https://www.plazajapan.

11

After re-reading my original post where I mentioned shaft-seal garter springs my brain started whirling around again.

I looked up a few sites and was surprised to find that you can buy the garter springs separately.

https://www.oringsandmore.com/stainless-garter-springs-for-14mm-shaft-minimum-2-pcs/

So now I’m wondering if I measure the circumference I need (roughly two inches) and find a spring diameter in the 1.25-1.50 mm range we might be in business.

The site above doesn’t mention the actual diameter of the spring. This site in England has some at 1.5 mm.

https://simplybearings.co.uk/shop/Seals-Rotary-Shaft-Seal-Replacement-Stainless-Steel-Springs/c19_7557/index.html?selection=Replacement+Stainless+Steel+Springs+for+Oil+Seals

I wish I was still at GE. We had hundreds of various shaft seals with these garter springs. They all went in a dumpster…

Here’s an outfit in Louisville that will custom make springs of the type we need:

https://www.acewirespring.com/garter-springs.html#

Regards, Ed

12

Thanks for the detailed message, Ed. I’ll let you know if the UK vendor from eBay replies back.

Forgot to mention that I picked up a NWSL can motor (PN 2032D-9) as a replacement for the power-hungry Pittman motor. It came with a 2.0mm shaft. That requires a 2.0mm (ID)-to-2.4mm (OD) bushing (NWSL PN 10169-9) in order to use the knurled pulley:

It’s also going to require fabricating a motor bracket out of 1/16" x 1/2" brass strip.

I picked up the K&S brass strip at my local Ace Hardware and have a design for the bracket. I just need to sit down at my bench and go to it.

Sure wish I had access to a milling machine like I used to when I worked down at Case Western…

Tom

13

I measured the old springs and they are 2.3" long.

The O-ring springs would be great. Unfortunately, you need to be able to disconnnect them in order to slip them around the knurled pulley in the small gear box. The only way to do that is to dismantle/unsolder the gear box housing. [:(]

Tom

14

Thanks for the heads up on that bushing, Tom. Looks like I may as well order enough for both engines.

Is the 3mm length good enough to support the knurled pulley? I wonder if I need two to give me a 6mm length to support the pulley on the shaft. I haven’t measured the length of the knurled pulley.

I remember messing around with the garter springs from old oil seals I pulled out of gearboxes I was rebuilding. You could separate them and re-connect the ends on most of them.

That outfit in Louisville looks like they would put any kind of end on that you specify. I wonder what their minimum order is. Might be worth an email quote OR send them a spring as a prototype?

Even if the garter spring is joined as a continuous circle you could simply clip it at the joint and bend a new loop in the end to make an eye.

One more thing I suggest. Don’t try to join the ends of the springs while the motor is in place. Loop the springs around the truck worm shaft then bring them up through the floor and join the ends.

Then carefully work the motor in place slipping the looped springs over the shaft ends and finally screw the motor in place.

It is nearly impossible to try to stretch the spring to try to join the ends while on the knurled pulleys.

Mamod was big into live steam. They made some neat stationary engines as well as some steam traction engines. One of thei

15

Just a thought; reciprocating compressor piston rod pressure packing utilizes metal ‘garter springs’ to hold the ring segments in place.

Regards, Peter

16

You’re bringing up some more of my GE memories, Peter. We did work on quite a few various compressors with the segmented packings and you’re certainly correct about the retainer springs. I seem to recall the ones we had the spring was a bit larger in OD, like 3-4 mm or so.

Hydrogen Compressor by Edmund, on Flickr

One day, before I started there, that eight-foot diameter flywheel snapped off and skittered across the floor!

Fortunately there was a foot-thick wall handy to stop it.

Hole made in wall by flywheel by Edmund, on Flickr

Thanks for your help, Ed

17

Ed,

I measured the length of both knurled pulleys and they were 0.297" on my model. The bushing is 0.118" long so you could technically use two end-to-end press fit inside each pulley. I wonder if the set screw on the knurled pulley would be long enough to bite down on the 2mm drive shaft of the motor?

Similarly, I asked NWSL the following question about the bushing in a Dec '22 email to them. (I asked it for both the knurled pulley and the plastic sprocket)…

Q: The bushings do not cover the entire length of the brass pulley or the plastic sprocket IDs. Should the bushings be placed on the end of each hub (right side, as pictured) where the spring drive belt and the chain drive apply the most downward force?

A: The motor has a 2.0mm diameter and that should be stiff enough to hold. Best practice is to get the part as close to the motor shaft bearing as possible but sometimes that doesn’t work.

So, maybe one bushing is adequate in the knurled pulley? The bore in consistent all the way through so adding another bushing shouldn’t pose a problem.

NWSL states that the bushing should press fit into the knurled pulley but also stated that pinning maybe necessary “if you get some undesired spin on there”.

Ed, I don’t know if that helps for just muddies the water…

Tom

18

The bushing does press fit into each knurled pulley, although with not much effort. Here are both pulleys outfitted with one bushing each and secured to the NWSL motor shaft using the brass set screw of the pulley:

The brass screw secures them well. However, I think I would like to substitute them with slightly longer ones, if possible, so that more threads of each screw engage the threaded hole. Also, if you added the 2nd bushing, it would interfere with the set screw binding onto the motor shaft.

Tom

19

Hi Ed,

The seller from eBay for the Mamod spring drive belts finally got back to me this afternoon. He apologized for the delay in responding. He stated he was away for a family funeral.

The seller told me the springs were 1.5mm OD and that he "plans to reinstate overseas shipping hopefully in the next 10 days. I told the seller I would check back with him the middle of March. As soon as I can confirm that he can ship to the US, I’ll let you know, if your interested…

Tom

20

That sounds great, Tom. I can split the order with you and cut the shipping fee by 50% [Y]

One of the people that follow my Flickr photos mentioned trying heat shrink tubing over the motor shaft to raise the OD to 2.4mm. I might try that just to see what the results may be. I have several wall thicknesses of small heat shrink to experiment with. In a low speed, low impact environment like this the heat shrink might just do.

I looked at motors with 2.4mm shafts and they all seem to have a huge current draw and even worse stall current!

https://nwsl.com/products/motor-round-can-double-shaft-2-4-x-17mm-12v-dc-8-5k-rpm-stall-1-9-a

Regards, Ed