Hello All-

We (the Stewartstown Railroad) have a Plymouth ML-8 that we're in the process of getting back on the line. We're in pretty good shape - a couple of radiator cores to repair/replace, brake asjustments, etc.

One thing we'd like to do is take up the slack in the drive chains. For those not familiar with this little industrial locomotive, if has two axles, each driven by a chain.

We don't have a manual for this locomotive, and we don't see any obvious adjustment points.

Can anyone offer any advice or ideas? Or better yet, experience with this type of locomotive?

Thanks

Mike Ruane
Volunteer, Stewartstown Railroad
www.stewartstownrailroadcompany.com

When I tinkered with one of these (ex-Chris Craft), I didn't see any means of adjustment, either. But I think I recall that the cast-iron pedestal liners were of two different shapes. By swapping them, you could move the axle back and forth. Maybe the scheme was to lengthen the wheelbase after the chain wore, and then start over by removing a link, or getting a new chain when it no longer matches the pitch of the axle sprockets.

A loose chain didn't seem to matter, but if you're covering miles with this thing, you might worry about the effect of a worn chain on the gear teeth.

Aarne Frobom
Schwinn City, Michigan

Plymouth also, on some models, had shims that could be moved from one side of a journal box to the other. In any event, the chain should have a minimal amount of slack, not zero, but not far from it. The looser it gets, the faster it will wear the sprockets, and you don't want to know what those cost these days. If it get very loose you run the risk of having it climb up on the sprocket teeth. This results at minimum in a broken chain, but can also lead to a bent or broken axle.

At some remote date in the 1960s I got a cab ride in this loco. I can still remember how incredibly noisy it was. Those used to the ease of operation of the typical diesel-electric need to try this sort of loco some time. Manual non-synchronized 4 speed shift, manual clutch (REAL manual, as I recall), and a throbbing LeRoi gasoline V8 of something like 1504 cubic inches. That's a REAL loco.......

By the ML-6 & 8 Catalog posted on the Arizona Railway Museum's website: http://www.azrymuseum.org/Projects/Plymouth/Plymouth_Catalog.htm


It says that `The (axle) boxings are retained in their proper position by chilled iron slides which are held to the frame by large bolts in slotted holes and backed by shims, this providing easy and positive chain adjustment'

From the photo on the page it looks like you have to climb inside the frame and shift the axles using the shims (moving a shim from the outboard side to the inboard side). If this is not enough to take out the slack you will need to start removing links (or substituting half links) from the chain.

Rich C.

Hi

I was kind of amazed at the amount of slack in the chain on the Goose I rode i this past fall. Seemed to work Ok, but they weren't trying to pull bunch of cars with it.

Cheers--Karl J.

Mike, the Rochester and Genesse Valley RR Museum in Rochester NY has a Plymouth Model BL-2 (1919) with chain drive to both axles. There where (and may still be) some pics on their website. There is an intermediate/idler shaft that is chain driven from the transmission (a very simple friction transmission). This shaft then drives front and rear axles via chains. Three chains in all.

The Pedestals have cast iron blocks (front and rear for each pedestal) that have wear liners screwed to the wearing face. On that model those blocks are reversible. One block is thicker than the other. By placing either the thin or thick block between the journal box and the idler shaft you can get about 3/4" of adjustment of sprocket to sprocket center distance. This gives you 2x 3/4" = 1-1/2" (one chain pitch on that model) of chain length adjustment. And it changes the wheelbase of the locomotive (only by a little bit).

On that model the intermediate shaft bearing blocks are mounted to the frames with slotted holes. There are adjustment bolts with lock nuts to move the shaft forward/rearward to balance the slack between the two axle drive chains. But this adjustment interacts with the transmission output shaft sprocket which has no adjustment (on that model).

Remember, you do not want the chains too tight since the axle sprockets will move up/down (relative to the frame) as you go over dips/peaks in the track. If you have trouble putting the joining link in you probably have the chains too tight. You should see at least 1" (probably 2" or maybe 3" depending on the chain length) of sag on the chain segments between the sprockets.

At the speeds and loads encountered by these size locomotives the sprocket/chain loading and wear is pretty low. The BL-2 in Rochester still has the cast iron (I believe) sprockets that where on it when it was recovered after sitting in a field for about 4 decades. They may be the original 1919 sprockets, no way of knowing. The "bottom" of the sprockets have some corrosion from snow/water exposure and have lost about 1/8" of their original profile (an eyeball estimate). But the ride is pretty smooth although quite noisy above the engine noise from the straight pipe muffler we put on the 4 cylinder Buda engine.

FYI, If you need to replace the chains, as of a few years back McMaster-Carr was selling those larger chains in 10 foot sections. Most places only sell 25 foot lengths, and we needed 27 feet. We had to break it up into three orders since the total weight maxed out what UPS/FEDEX (tm) would handle in one shipment (75 pounds If I remember correctly).

There are lots of old engineering textbooks on the web about chain drives with information about loads, speeds, slack, etc. These Plymouth chain drives are over engineered by a factor of about 10. The Buda gasoline engine puts out about 75 horsepower. A modern (hardened steel sprockets) 1.5 inch (pitch) chain drive is good for about 5000 horsepower at 500 rpm (when properly lubed and aligned). We only had to replace the chains because they where rusted solid. We did not do any other adjustments. But we never hauled more than one car either (about all that little BL-2 can handle on level track anyway).

Good Luck, Cheers, Kevin.

I never helped adjust chains on a Plymouth, but on Brookvilles you loosen the big bolts the hold the journal pedestals to the frame, then adjust the axle out with the setscrews to lengthen the wheelbase and draw in the chain. If you have far too much slack, look for a half link in the chain and take that out. But don't adjust the chains until you know for sure they're too loose, wait until the unit is running.

Some guidelines for the right amount of slack can be found here:

http://www.cisco-eagle.com/service-maintenance/scheduled_maintenance/conveyor-maintenance/belt-tension

http://www.maintenanceresources.com/referencelibrary/rollerchaindrives/installationpg1.htm

Nick

Nick, good references, thanks for posting them.

But remember they are for "fixed" machines where the spacing (horizontal and vertical) between shafts is "permanent". Once you add in railroad axles that go up and down because of track "roughness" you need to add a bit to those numbers. I think for a two foot sprocket to sprocket span a ~1-2" "sag" in the chain is probably about right.

In theory a chain that is too tight might (I repeat might) suspend an axle above the rail-head and cause a derailment. But I admit that is very unlikely.

These chain drives are really quite forgiving, I think the owners of the ML-8 might be wise to forgo removing the slack from the chains until they have more info that it is a necessary step. Run it slow, watch the chains, if they tend to run in a straight line (no "bunching" where links on the "slack" or unloaded side are compressed together) you are probably "good to go".

Also, you can never oil a chain too much, we added brush oilers to the chains on the Plymouth BL-2. Yes it's a bit messy, but that's just the way chain drives are. Anybody else ruin white pants getting them caught in the chains on your bicycle ?

Cheers, Kevin.

Kevin - and everyone else -

Thanks for the info. The next time I'm out there I'll get down in the pit and see if I can locate any of these suggestions and tighten up.

Thanks again-

Mike

On the Niles Canyon Railway we have a JLA that is used as a shop switcher. On this locomotive both chains are slightly loose. One is about 1/2 a link too long, the other is just under a full link too long. We have had no issues with running the locomotive chains loose.

Kruger-
IS the locomotive blue carded? Any FRA issues with the chain slack?

MIke