Cheap Smoke Unit Motors?

Well that's interesting to me that the blower performance is not well known. I did a research task a few years ago where I looked at commercial micro blowers which is what these motors are driving, and not fans like everyone likes to refer to them. Fans move a bunch of air but only against low resistance. Blowers are what you need to "push" air thru a resistance like the wick and chimney stack. As a rough guess you could say that the blower cavity cylinder is about 0.1 in3 in volume. Subtract the impeller volume and you get about 0.05 in3. That gives the maximum air volume that the blower can deliver with each revolution. With tip clearance losses figure 0.025 in3 real performance per revolution. So for every 10,000 rpm you would get something like 250 in3 per minute of smoke output. If the little motor is whining away at 20,000 rpm then you would get 500 in3/minute and so on. For most in the modeling community this information falls in the "who gives a crap" category but it shouldn't. High rpm is tough on motors (and ears). Also the flow of air to create the smoke output is what is keeping the resistor from cooking the surrounding wick and burning up. The whole cycle from air entering the blower to smoke coming out of the chimney is a complex physical process with a lot of itty bitty parts that have to work right in a small space. THAT is why smoke units can be so fickle from one engine to the next.

Well, the problem with all of this information is there's really not much you can do about the motor RPM or the impeller.  I do drop the drive of the motor in the idle state with my Super-Chuffer, but I can't drop it too much or a marginal motor will stall.  I position the resistor and wick in the most optimum place for the best smoke performance.  I also adjust the power to the resistor by changing the value to achieve the desired effect. 

Since I can't really change the characteristics of the motor or impeller without a lot of expense and research.  I suspect that's why the "don't give a crap" pervades the topic.

Personally, I think much of the smoke differences can be laid at the doorstep of properly installing the wick, selecting the resistor, and also the positioning of the resistor.  I can get very good smoke out of most fan driven smoke units with a little work.

That's the neat part. With correct wick arrangement and resistor selection I'm not surprised that any smoke unit should be able to work really well. And yet, in general smoke unit performance is one of the most griped about features on different engines. It would seem to me that both Lionel and MTH should welcome a little technical help in this area. A good example is the well known problem with the shallow draft angle on the Legacy twin stack diesel manifold. Smoke oil gets hung up in the manifold so not only does the wick not have oil, airflow has a hard time getting out as well. End result is a cooked wick and dead smoke unit like my GP9 .

I think you have hit in a major area of problems, the piping from the smoke units to the stack/whistle/blowdown.  There's great smoke at the outlet of the smoke unit, but it gets subverted before it is seen.

Exactly.

I have two Legacy twin stack diesels. One is the GP7 in the thread I posted on loss of speed control. Like the GP9 smoke production was lousy. While I was working the loose flywheel problem I popped off the top access panel for the smoke unit -- really easy to do. Then the fill/smoke manifold -- also easy. I blew the manifold clean of fluid with compressed air and added smoke directly to the unit stack. Replaced the manifold and the panel and it smokes like crazy. If I had known to do that with the GP9 it probably wouldn't be dead now.

For all the forum posted complaints -- "why doesn't my smoke unit work and shame on you Mr. train-maker blah blah!!" -- I don't think Lionel (and MTH) are trying to produce problematic smoke units. They are doing their best to pack lots of functionality into a small space. This squeezes the space available for the manifold creating the shallow draft angle in the case of these Legacy units.

If I can get the tech information I need I may try to submit an article abstract to a trade publication I support. Most of their articles have been pretty dry lately and this would be a fun subject.

Thanks for the replies BTW

I recently did a Super-Chuffer install in the scale Challenger.  I had to really chop the silly wedge in the stack so that the smoke would come out both stacks.  It actually turned out pretty well, but the factory design had 100% out the rear stack.

Once installed some one needs to log run time to determine MTBF, also track any other issues.

I am sure some may be Mabuchi, possibly out the back door and onto ebay.  The other possibility may be counterfeit.  What that means is unknown until we get some reports.

Put on in a Legacy and lets see if you get 3 blinks off the bat.  G