There is a long (12 page) discussion going on over at the "Railwire" N Scale forum entitled: " "Science" of Solving N Scale Diesel Mechanism Drivetrain Vibration Noise". Those N scale mechanisms have a lot more "going on", such as flywheels, universal joints, etc., but I'm hoping someone here with a lot more experience than I have might read this, and come up with a similar application for the Micro Trains F7. If not, it's still well worth reading. Mark in Oregon
Perhaps; I'm not familiar with David's work...link? What I find most interesting about that thread is that the focus is, as the title reads, on the "drivetrain" itself. I'm wondering if most of that famous "grinding" noise we're all so fond of is being created by something other than the motor. I know that if you take the motor out of the frame and run it, it is practically silent, so it would seem that that noise is coming from something else(?) I'm gonna look at one of mine and see, for example, if there is some sort of universal that can be fitted to replace the "belgear" set up; I would think that might be a good place to start... Mark in Oregon
The trucks and the bell gears definitely account for most of the noise. The other thing is the shell amplifies the noise. Try it without the shell. I have put thin tape inside the shell to reduce vibration which make things noisier. Spur gears are just a noisy design, but I think the type of plastic could also contribute to the sound. Trey
Trey You're absolutely right about the shell amplification, and the trucks, which don't roll on their own worth a darn. But here's something else: I have a Marklin V 216, and although the start-up speed leaves a lot to be desired, it is MUCH quieter than any of my MT F units. It has a more "complex" gear system, yet as I say, it is not nearly as noisy. Thoughts? Mark in Oregon
6 or7 years ago Glen Chenier wrote several articles on improving the performance of MTL's F7. Sadly Glen passed away a couple years ago but his articles can be found on Yahoo Groups Group "MTL Z Scale Locomotive Maintenance" its free to join and does not require approval. Once you join the group click on "Files" then on "F7" to display the list of articles. I don't know if this will work but i will try and add some direct links to down load his Articles. Why Model Locomotives Stall https://xa.yimg.com/df/MTL-ZScaleLo...aQ8wMg-9j_FJzDJCWJZcF8vjKEvskoA&type=download F7 Motor Cleaning https://xa.yimg.com/df/MTL-ZScaleLo...2o4qGycPNMri0yXZsqGhO1a5Rki03Og&type=download DCC and Overhall MTL F7 https://xa.yimg.com/df/MTL-ZScaleLo...HkwBqV5aUOenRTuSIgDZsmQIVL1B0q3&type=download Wheel Wiper Installation Instructions https://xa.yimg.com/df/MTL-ZScaleLo...9I5tF_zVRDBah3qNY_R5zu2RpxE9GWc&type=download Addendum to WW Instructions https://xa.yimg.com/df/MTL-ZScaleLo...M9CGU5bouQNM_M4Lu1MrCn7MDqkWVZA&type=download If anyone is interested in a set of Glen's wheel wipers email or message me. I have the last of what he had in stock at the time of his passing. David
Just a general note on gears and tooth profiles, one of the keys to noisy running gears. Theoretically a gear tooth is machined with a straight face at a chosen pressure angle that optimizes the strength and mesh of the tooth. BUT any time gear sets are rotating as they mesh, the tooth engaging faces must be radiused to mesh smoothly, smoothly rolling in and out of the mating tooth, maintaining that theoretical pressure angle. That radius dimension changes every time a tooth is added or subtracted because the rolling angle of engagement has changed at each increment of rotation. The result is that each gear pressure angle and then number of teeth at that pressure angle results in another unique tooth profile. This is true of all rotating gears but is not required on the rack only side of a rack and pinion or the worm side of a worm gear set. The faces on those project straight out at the pressure angle dimension because the rack or the worm engages the mating gear at that straight angle, moving only linear, not requiring that rolling, smooth meshing effect. The pinion gear or the worm gear in a mating set, because they DO rotate in and out of engagement, require the tooth face to be radiused so it can smoothly roll in and out of mesh with the mating linear moving tooth. NOW, with that background, keep in mind how these parts are often made. They are molded plastic. That means the designer must first calculate and draw the radius perfectly and then the machinist must machine that radius in the mold perfectly, both sides of every tooth, holding those dimensions to extreme tolerance on every increment of every tooth, if the parts are to mesh quietly. And I do mean extreme tolerances. In the light duty that these see they can perform acceptably when the faces are less than perfect but each imperfection results in an acceleration or deceleration of the gear at each imperfection, the effect is immediate at the point of mesh, and when less than perfect it's a whole series of minor impacts that transmit sharp forces that result in sound. If the gear was operating near its theoretical load capacity or in rigid material with no impact absorption characteristic it would also result in early failure. Fortunately we aren't there. The load and the material characteristics tolerate that action but the noise doesn't go away. NOW, introduce the computer to the designer with a good gear program and its ability to do the massive calculations required to calculate the infinite number of points, the latest CNC controlled machines that can respond to ridiculously fine corrections, and what used to be a near impossible task becomes doable. And that's where the newer gear trains have a good chance to run quietly. As the costs of that equipment have come down manufacturers can afford to invest in and take advantage of it. It's still costly but not nearly as bad as just a decade ago. And here we are. You can still do what you can to assure that meshes are appropriate and all fits reasonable, no binding or absurd slop, no loose parts vibrating about the mechanism, because they are all part of the noise generation and they matter but at the end of the day, the worse the profiles, the more noise you will have. And absent a total redo of that faulty gear there's nothing you can do about it. And many of the gears made over time aren't so good in this area. Hope that helps with some understanding.
David Thanks. Yes, I am well aware of Mr. Chenier's good works. Without his extensive research, I doubt if I could ever have re-built my first F7. Interestingly, I have never had any issues with electrical pick-up from the rails. Guess I've been lucky! "Tracktoo" You make a lot of good points; not so different from what's being said over on the "Railwire". I just totally disassembled, cleaned and did some fudging with the loudest of my (4) F7s, and it's no better (or worse!) than before. It runs better and quieter in reverse for some reason. I have to think that some of this model's "quirks" lie with those trucks; I posted a thread last week about how poorly an unpowered unit rolls, and a powered unit has the same trucks, so doesn't it stand to reason that, at least to some degree, the trucks at the very least add to the problem? A free-rolling mechanism should be a quieter one. I took a close look at the trucks on the Marklin V215; the frame proper is plastic, (and so it has a vastly different pick-up system) and the axles are not as robust (thick) as on the F unit. And as I mentioned earlier, although it has an additional set of gears, it is much quieter. I would think there might be a demand if someone could come up with a free-rolling replacement truck for this old war horse. Mark in (very wet) Oregon
Mark, this is also Mark. It's probably a gear profile problem which could be aggravated by gear pin locations/ spacing, but sight unseen and knowing what I know and have seen, I'll bet it's the gears themselves as described in my previous post. The truck body and pin locations aren't that hard to hold adequate tolerance on with long standing manufacturing methods but the gears... that's another story. There is a guy in Poland who sells custom gears of this type and by reading his extensive list of product offerings I suspect they will be quite satisfactory because I suspect that he's hobbing them. That's a more costly way to produce them than molding as they are individually machined in a true gear hobber (or live tool lathe with custom tooling for little gears) but it's about the only way to make one offs with any efficiency and by virtue of the process and reasonable care on the part of the operator they will have the proper involute profile. The process generates the profile by virtue of the cutter and the gear rotating in unison engaging with each other in the same fashion that they will when running in a device. This method generates the proper profile by default and is the common method for making machined gears. His prices are very decent for this method of production but is more than high volume molded would be. I think he averages about $5 give or take for each gear. So there's the rub. It could probably be fixed but at what cost? Hmmm. I would have to look through my notes to find a link if you wanted to persue that.
While there is no doubt their would be some interest in a newer better built replacement truck for the F7 It is very Unlikely to ever happen. While there are many who are not afraid to work on their own locomotives Id venture to say 1/2 the people who have z scale don't even know how to take the shell off the chassis. and of those who do know how, less than 1/4 of them would be willing to attempt or be able to diss-assemble a chassis replace the trucks and reassemble it. AZL sells their replacement trucks for $35 each How many people do you think are going to be willing to spend $70 to upgrade the trucks on their $90. locomotive? or even $25 for replacement trucks on their $50 dummy unit. Your potential market is just too small. You would never sell enough of them to recover the 10's of thousands you would have to spend on molds and tooling just to have the new truck parts and gears produced. David
As long as the gears aren't binding anywhere they can probably be made to work satisfactorily and maybe even quieter than one that's binding but the noise will always be present if the profiles aren't proper. That's my best guess, sight unseen. I would be happy to look at one of these if someone wanted to send me one. With an in hand inspection maybe something would surface that would help.
Thanks guys, for responding. Any feedback is useful. Speaking of gears, the original F7 I got (the one that was basically "DOA" when I got it) has what almost looks like fibre worm gears; my other (later ones, I suspect) have plastic gears. Yet the plastic ones are no quieter than those earlier ones, which kinda surprises me. And again, the Marklin V215 (which I keep referring to in this thread as it's the only other diesel I currently have) has all metal gears, which you would think might create more noise...yet it is really quiet. I know I'm probably "beating a dead horse" here, but what the heck; the World Series doesn't start 'till Tuesday... Mark in Oregon
Bad tooth profile. Good tooth profile. The tooth profile and correct spacing will run smooth, therefore quiet, in any material. Maybe think of it as a hard wheel rolling on a hard surface, one with little bumps on it and one perfectly smooth. Speed it up and load it up and what do you think will happen. Depending on how bad the bumps are both may roll but I'd expect one to be ... and one to be .
Some time ago now I saw pictures of re-powered F7, using a Faulhaber can motor same size as used the the MTL geep and SD40-2, the new motor was held in place in a squared off opening where the original motor was located, at each end of the motor a plate supported the motor in the space, in a similar fashion to the motor in the MTL Geep chassis. The plates kept the motor aligned vertically and horizontally and left space for a Z2 decoder, to line up with the worm gear shaft in the original bearings and bell gear was removed and a surgical tube coupling was used between the motor shaft and the worm shaft, other than a change in the gearing, the most noticeable change was the reduced noise in the unit, the project did not seem to get further due to the cost of the motor, several other motors were suggested but do not recall any further work with a different motor. In my own experimenting at the time I was able to purchase several MTL bare chassis and I found that when I created a n FP7 shell from a couple of F7 shells that the geep chassis fitted perfectly, and I took a an example of a cut down MTL Geep chassis done by David K Smith for a MP15 chassis and created a chassis to fit under an F7B shell, I used a bunch of those chassis to power some of my custom Nn3 and Z items, including the veranda turbine, and the hallmark PA shells,
Mark If that offer was directed at me, thanks (!) but I think I'll just park that dummy unit for now... Garth Interesting: One the major builders of 2 rail O scale swears by Toyota vacuum tubing for his re-builds, in leu of universal joints, etc. Sounds like your subject was kind of going along those same lines, but using the surgical tubing instead... Mark in Oregon
