Postwar 675 Smoke Unit Question

No tube or anything between them. I'm having trouble envisioning the gap you're talking about so I don't know if that's a problem or not. I would think that if there was a gap under the shell, the smoke would be puffing inside the shell instead of out of the stack though.

Are you sure the piston is falling back down between "puffs"? Sometimes they get gummed up with either fluid or pill residue and they don't drop back down like they are supposed to. Some (most, all?) engines  had a spring that went between the piston and the reservoir  to  make sure it went back down. If yours doesn't have the spring, perhaps adding it might help. 

Is the smoke unit still the wire wound pill type, or has it been converted to liquid at some point? If it's liquid, sometimes the sleeve that goes over the heater gets charred and doesn't soak up the fluid as well as it should, causing poor smoke output.

I hope some of this helps,

J White

Clearly, there should not be a place for the air to escape and not go into the smoke chamber.  I don't have one to look at, but in the Lionel 675 Repair Manual it appears there is some sort of gap.  I have a couple of mechanical smoke units in my parts box, none of them have a gap like is illustrated here.

The gap is normal. There is no tube between the cylinder and the smoke pot on any postwar pellet type smoke units.

If you are getting poor puffing action, it could be a few things:

1 - you've put in too many pellets, there is a lot of material in the smoke unit, so it is not getting hot enough to make much smoke. The smoke stuff stays in there from operating session to session. Make certain the old pellet is used up before adding another.

2 - the air passage is clogged.
Using your fingers or a pin vise, run a small drill bit up through the hole in the cylinder, up into the smoke pot to clear the path.

3 - your piston isn't going up and down.  Clean the cylinder and piston with a rag to remove any old smoke material, and any grease or oil.

You can put a 2026-44 smoke unit spring in the cylinder to help the piston drop.

Yup, that's exactly what it looks like.  I rebuilt the unit not so long ago.  It worked great then suddenly stopped.  I wish I'd made a mental note at the time, but I didn't when I rebuilt it.  I think some sort of little tube fell out while running.

However, my other thought is the chamfered hole in the reservoir was the to "catch" air being blown over the gap.  Perhaps they designed it this way so the piston doesn't suck air from the smoke chamber on the return stroke.  In any event it doesn't work all of a sudden, I bet the tube fell out.  Piston has a return spring, runs perfectly, element makes smoke, it just sits in the bowl unless you get a ton of speed then it wafts out like the piston wasn't moving, which it is...  Hole is clear, I can see light, right through, clean as a whistle. It has been converted to a liquid element, but it really shouldn't matter, wick is not charred, it DID work then it stopped.  There's not a lot to these units.

I've rebuilt lots of these lately (I use 3M fiberglass woven sheet from the auto parts store, it holds and wicks fluid better than anything I've found, even tiki torch, and you can do a ton of engines (50 or more?) for $6

This is one bizarre smoke unit.

I have a 2035 (same loco) and it does not smoke well, even with a completely rebuilt smoke unit. The problem is, it runs very well and at a low voltage (even with the e unit on) and only smokes well with a long heavy train and/or high speed. My other post war spur gear driven locos require a higher voltage to run and they smoke better. Could it be your 675 is just a finely tuned well running loco that does not require much power to run?

Yes this one is very efficient compared to most.

On this particular unit, I added a diode ladder to the motor to up the voltage.  It smoked like a banshee. But, like I said, the wick isn't charred from too much heat.  It smokes, just doesn't puff.  and the hole is open and piston works.

I think what I'm going to do is drill out the hole and line it with a brass tube down to the piston.   That GOT to be what's going on.  Perhaps a PO had squeezed a makeshift tube between the gap and it fell out. (I really wish I had paid more attention now!)

And there is no debris in the gap?

When you say the hole is open, do mean inside the smoke pot too? The smoke pot has a tube cast in place. It goes up and terminates never the smoke pot cover. Maybe some of the fiber smoke liner is covering the end of the tube. It has to be completely unobstructed.

Check the resistance of your heating element. Some of the repro ones had a higher resistance than others. I think 16 ohms is preferred. 18 or 20 ohms will not smoke as well. If its higher than 16 you can unwind a few turns to bring it back to 16. Unwind it from the side than is pressed to case. You can't solder to nichrome but pinning it between the top and the case will provide a good ground.

Pete

I have rebuilt many postwar smoke units, and have quite a few NOS ones stilling in my parts drawers. They did not leave the factory with a tube between the cylinder and the smoke pot.

quote:

Check the resistance of your heating element. Some of the repro ones had a higher resistance than others. I think 16 ohms is preferred. 18 or 20 ohms will not smoke as well. If its higher than 16 you can unwind a few turns to bring it back to 16. Unwind it from the side than is pressed to case. You can't solder to nichrome but pinning it between the top and the case will provide a good ground.

Newer reproduction elements seem to be better on resistance. If you have one of those high resistance smoke elements, I find that removing one turn is usually enough.

I mean it's clean as in brand-new condition clean.  Not a speck of anything.  No obstructions.  I had just rebuilt it about a month ago.    Yes both holes, no obstructions.  No fiber blocking it.    I bet a tube was crammed in there.  because it smoked almost unreasonably good.   Now it sounds like it's closer to Jeff2035's

Are you actually SURE the piston is moving, not just the piston rod? The piston is spring loaded and the crank connected to the piston will move back and forth with the side rod movement but if the piston's lower lip is hung up with the screw that holds the smoke unit in place it will not move, although the piston crank is moving back and forth. It has got to be that if the heater is still working and nothing is blocking the air port in the smoke unit. The gap has no connecting tube.

 I almost forgot early 675 engines don't have the spring loaded crank, A spring can be added in the cylinder to correct the problem if the piston is sticking in the cylinder.

quote:

Now it sounds like it's closer to Jeff2035's

Then it could have excess smoke stuff. If there is a wick, I guess you converted it to use smoke fluid.

Chucks point about a jammed piston certainly could be the cause too.

I don't know how it got that way, but not all that long ago, I had an engine on my bench that had the piston wedged tightly in the cylinder, all the way up. It was a bear to get free.

I just cut a piece of PEX tubing I had laying around and shoved it in the gap.  It smokes like it used to!  I'm going to add a brass tube. 

The gap is there for a reason. It allows the downward traveling piston to suck in some fresh air for the next upstroke. If you seal off the gap, the down going piston will suck the air back out of the smoke chamber with a net result of little to zero output. I once used your same logic and did some experimenting with some o rings to make the seal, and that's how I learned. If you had success with closing it off, it's probably because you unstuck the piston, as Chuck suggested, while dinking around with the unit.

I agree it isn't the most efficient way to do it, but it works. The Lionel engineers weren't dummies, and if it worked before you should be looking into some of the other suggested solutions.

I'm really surprised GRJ is perplexed by all this-- all the pellet type postwar units have a gap between the cylinder and bowl. Nothing unique about the 675, as far as operation goes.

P.S.  Also, resist the temptation to enlarge the holes to attempt more output. The smaller holes deliver more velocity to bridge the gap. Again, the original engineers were pretty smart guys, and I really doubt the first iteration became the final product.

All I can say is I installed a tube and it smokes great.

Take out the tube, nothing.

It ain't the piston.  1000% Guaranteed.

Maybe mine's weird, but that's what worked and I'm smokin' up the room.

The reason I'm perplexed is I rarely work on the pellet smokers, I tend to do a lot more work on more modern stuff.  None of the fluid smoke units I've seen have a gap, at least I never noticed it while working on them.  I have several in my parts box from fan driven upgrades, they all are tightly sealed. 

I don't argue the fact that there's a gap in the 675 smoke unit as I see it in the pictures.

Since many of the puffers don't have any gap there, and they smoke fine, I suspect the air gets sucked in around the piston on the down-stroke.  Some of the smoke pistons also had little ball bearing check valves to allow air to go through on the down-stroke, but I question how well that worked.

quote:

The reason I'm perplexed is I rarely work on the pellet smokers, I tend to do a lot more work on more modern stuff.  None of the fluid smoke units I've seen have a gap, at least I never noticed it while working on them.  I have several in my parts box from fan driven upgrades, they all are tightly sealed. 

The older Modern era liquid smoke units that are just pellet type units with slightly different guts still have the gap. I have an 8206 in pieces right now that is made that way, along with a couple of spare smoke units in my parts box.

Postwar Lionel's liquid smoke units were of an entirely different construction. They were also carried over into the modern era.

Which smoke units do you have without the gap?

The units I have came from upgrades of stuff, usually from the 80's or later.  I only have a few right now, here's a sample,  I can't even tell you where most of these came from, but none of them have any gaps.  The really odd one was in a K-Line locomotive.

I sure don't see any gaps in any of them.

John, the pistons are valved in your puffer types that we can see. No valves in the postwar puffers.

Actually Rob, those "valves" are dummy depressions, there is no hole in the piston for many of them.  The two in the middle do have the two check-valves, the others don't.  The one that has two holes are just that, but they don't go through.

Ah - hard to tell in photos. I don't have any like that.

John: Thank you for posting those pictures. I have not run across any of those smoke units. They weren't used in Postwar Lionel Trains, or in the Modern era stuff that I am familar with.
The stuff I work on is older.

I've seen the valves, the ones with no valves, and some that have a flat piston with no sign they ever intended valves.  I suppose the ones with the two blind holes were just leftover mold remnants of when they were putting valves in them.  I find it curious they have two blind holes, they can't be functional, or at least I can't imagine what for.

Oddly, the one thing I never noticed was the gap when I had the older stuff apart.  Normally, you don't have to do anything to the pill units, they seem to last a lot better than the fluid type.

If its now working thats great.

Have several early versions of the  675 and 2025 and there quiet and smooth along with being decent pullers.

The smoke output when working properly blows nice smoke rings when running at slower speeds which these do very well .

After assembly and with the cross head back to furthest position one can use finger to gently push the smoke crank forward and it should come back with ease and can hear the piston dropping downward.

If not it may have the slightest bind as the smoke unit itself may be slightly cocked when it was reassembled and the piston not moving as freely .

Hope this helps others that may encounter unit not puffing properly other than the airhole being clogged over the years with residue even dripping down over the piston and impairing its movement.

As a note a few converted to liquid and smoke just as well and less expensive to operate.