A LOOK AT LIONEL'S CAB FORWARD INSIDE THE BOILER//PICTURES

I agree, maybe it was a poorly molded impeller or was damaged during manufacture.  If it was hot enough to melt an impeller without touching, you would see signs of overheating on the top of the PCB.  G

Thanks Alex, I appreciate the time you took in posting those mounting screw pictures. I'll document what I find when I get it apart..... 1st I gotta go get it from my Dad's house, we been running it lately with the smoke tunred off. 

Aha, good point; I had not thought of that but it's pretty clear once you note that it's only one part of the impeller that's melted. 

Yes, also right - as I found to my cost when I tried to "fix" a VL Challenger smoke unit, which is much the same design. That one made it's way back to Lionel.

Thanks for sharing the pictures...they have reinforced my decision to live in a "post war" Lionel world. Nice stuff though...

Alex

Thanks for posting, you have me thinking about a Cab Forward

Steve

Alex, I have been seeing burned (melted) impellers.  Great post.  The Cab Forward is one great locomotive.

It's interesting the impeller is getting melted.  That the one for whistle steam, so that resistor is maintained at a warm (hot?) temperature so you get immediate smoke, the impeller isn't running unless you are running the whistle.  Maybe that's just a poor design?

So you guys are saying to use 30 drops?  What does the manual say to use?  Seems like a poor design as far as distributing the fluid to both chambers.   They used to have separate units for main steam and whistle steam.  Now it seems the latest engines have combined one, like my Berkshire.  I notice the whistle steam on these combined ones seems weaker and there's smoke leakage even when not blowing the whistle.  Is this design to save space?  I hope these melted impellers aren't going to be a chronic issue.  So do you think adding extra fluid helps prevent that or is it just because the fan is not running all the time.  Seems like heat is building up.

In an interesting twist, the Vision Line Big Boy has you add fluid to each of the four smoke units.  They apparently are at least a little separate in there.

I suppose at some point I'll be forced to take it apart and see how it functions.

I was just going to ask who would be first to see what's in the big boy.  Haha.  I guess they have plenty of room in those for separate units.  Must be a space saving issue with the combined ones.  Maybe if they did not do combined ones some of these engines wouldn't be able to have whistle steam at all.  I just wish I knew how much fluid to use, it always seems like it's just a guess depending on engine.

Alex...this was very nice of you to give everyone a detailed look.  It helps folks to understand how it works and the importance of adding enough fluid to avoid problems!

You did good my Friend!

Alan

I learned a lot from the initial post! so thanks Alex.  

Very thought-provoking in terms of how much fluid to actually add.  My Railking N&W J steamer smokes like it thinks it's the real thing.  My Permier version not so much.  So I added 10 drops more than manual specifies and the Premier started smoking out of the front bottom. A beautiful steam effect, but probably not what the manufacturer recommended. I agree with an earlier post - it's a slightly frustrating guessing game knowing how much fluid is not enough versus too much.  

Peter

At some point your wick may have been burned on the Premier and that causes reduced output, also the top of your unit may be loose or the gasket was damaged.

Easy fix to get that premier working again.  Take the shell off and see if the screws are loose.  G

The point that Alex raises on adding > 20 drops of smoke fluid is one that Lionel needs to answer since the latest Legacy steamer manual say DO NOT ADD more than 20 drops of smoke fluid for the initial fill or else damage to the electronics could occur. If I am understanding Alex right if you don't add more fluid damage will occur to the unit?

Very interesting Alex!    Thanks for posting this.   Merry Christmas. 

The s3 and challenger have units like this except there metal but in general you have to add a lot of fluid in them together them to work Right to.. 

Ho, ho, ho - Merry Christmas morning.

You're right that Lionel advises against adding more than 20 drops but Mike Reagan's comment in the official Big Boy product demonstration video linked on another thread on the Forum discloses exactly why. A smoke fluid overflow can cause problems with the fan motor bearing, which Mike commented Lionel did not want to see cause a lot of BBs come rolling back into their service facility for fan repair/replacement. I have found this with one of my VL engines although I believe that the problem arises NOT from ensuring that the wicking is saturated on first use but from topping it up obsessively afterwards when you don't really need to.

I am a little concerned about the melted impeller problem especially as Marty F says he's seen a lot of these. I wonder about moulding a ceramic, heat-resistant impeller for the whistle side of these units if it is a design problem. Alternatively maybe it's best not to turn the SMUs on the high setting very often - at least without letting off "steam" very frequently!

After looking at those pictures again maybe it be smart to change those impellers with the older style ones that aren't made out of that style of plastic .. I can't see how those won't melt regardless .The resistors get really hot and there's no where for the heat to go.. Older units  they separated the motors from it .I really hope the big boys aren't like that .. This is just in my opinion..

From that one, it appears the issue may be that the smoke resistor is always hot for instant smoke.  The stack impeller probably isn't going to have that issue, at least like that on one side.  It's almost always moving, either chuffing or continuous idle when stopped.

Some while back when this thread started Jon Z. posted the following comment about the impeller issue:

"The Whistle stack stays heated - but at a reduced temperature.  The impeller should not melt.  I would get a replacement part Alex, the imbalance of the impeller will damage the fan motor from being out of balance."

It shouldn't melt but I suppose under certain conditions it might.

JoJo, not sure which older style impellers you mean. Checking over Lionel's replacement parts for these and similar smoke units, the impellers seem to range from .420" to .500" diameter and different heights.

The damaged one Alex pictured above is .430" diameter. Here is that one and a different Vision example from the Vision ATSF 9000 - a .450 diameter but also shorter: