I am looking into having tungsten alloy flywheels fabricated, and wanted to see if there was any interest in the N scale community. I plan on targeting the Atlas GP7/9 first, and if successful moving onto the other models. If you like the way the older Atlas/Kato GP30/35 lokies flywheel coast, these will give the GP7/9 similar characteristics. The new flywheels will be approximately twice the weight of the flywheels they replace. The hexagonal drive surface will most likely formed by EDM, as broaching this material may prove to be problematic. I am trying to get the first set done to ensure they will press onto the shafts correctly, and will post pics once I get them. The price per set of flywheels will not be cheap (working to finalize a price, and it will be quantity driven), probably in the $20 - $30 dollar range per set at this point. I am not looking to make a profit on these, only trying to see if I can get my own cost down by making a volume buy. Any interest?
Cool, I assume these would be made of an "easy to machine" alloy. Most of the tungsten I have played with have been powders or sintered powder that make different forms like cubes and cylinders. I can cut the and shape them with diamond coated abrasive wheels but it is slow going. Finely balanced fly wheels would be nice.
These will be about a 95% tungsten alloy, with the balance to be iron and nickle. I will be starting with round stock, cutting to length and machining the diameter. That part will not be too difficult and I am looking to perfrom that aspect of the operation myself. I had considered broaching the hex, but at the cost of the broach and the uncertainty of how long it would last, I decided to pursue EDM. What with the holidays and travel back home to visit family, it will probably be 3-4 weeks before I can get the initial set back from the vendor, but hopefully it will be worth the wait.
I would be interested in these if... they have a 1.5mm bore, their diameter is 10mm or less, they truly come in weighing about 1.5 to 1.7x as much as the brass version. (Boy... picky picky... ). I know, but I would want them for steam engines, so the hex cut-out doesn't matter to me, but a small size is important. 10mm is okay. 8mm would be better. Thanks for taking this on!
You should always Beardenize these Atlas short locos. If you have not done that I would. If you have done that, then the flywheel effect will indeed be more significant. http://u18b.com/wp-content/uploads/2013/03/Bearingblock.pdf
The problem I see...... Tungsten is much harder than brass and you can't rely on the "softness" of brass to make a reasonable friction fit on the motor shaft. Tollerances will be less forgiving so plan on a looser fit and use sleeve sealer or something similar to mount the flywheel. A solution may be to take the stock flywheel, turn it down to just over the size of the hex, then machine a Tungsten sleeve to go over the original brass flywheel. This cures the issue of broaching or expensive EDM to form the hex, makes the fit on the shaft easier to deal with, and the weight would be in the most important place on the flywheel, the outer rim. It seems a much simpler and less expensive solution and may be possible to deal with yourself without having to farm it out. I'm currious, how do you plan on machining the Tungsten, diamond tools or grinding?
The plan at the moment is to grind. Remember that it is an alloy (95% Tungsten) and we have already played with a couple of pieces. The fit over the shaft is my big concern, and I am going to try thermal expansion on the first installation. I am not sure of the expansion rate of tungsten, and my fear is that I may transfer too much heat to the motor shaft.
Loctite makes a product that will work but typical thread locker is not strong enough and doesn't have the right properties. You need Loctite 640 sleve retainer. http://www.etrailer.com/Tools/Loctite/LT37484.html
One thing to consider, the heavier flywheels will have an effect on the durability of the motor. There may not be enough torque in the motor for driving the flywheels, or that driving them will overheat the motor. This is from the lessons learned school of Hard Knocks.
I anticipate that the final weight of the flywheel will be close to those on the Kato built GP30. As such, I don't anticipate it to be an issue as long as it is properly executed.
I like Loctite 620, it holds great as is, can be removed, and can also be heat hardened. I have done 50+ motors for Atlas and Kato n-scale locos using 620. They also have 680, I use it on something that is suppose to be permanent.
John I am not saying it will not work, just be a little careful. Sometimes even small changes in load seen by a motor can have undesired effects. For example, if I understand things correctly, you are doing this so that scale speed motors in Atlas GP 7/9 units would glide like the older Kato/Atlas locomotives. I potential issue I see is the the scale speed motors do not have the same amount of torque as the older Kato motors. Those motors are not a strong as the Kato motors. This where the lack of torque may produce undesired results. Now if you are talking about older Kato/Atlas GN 7/9's, or you are using the Kato motors, it should be just fine.
I have the Atlas Scale Speed motors in several Kato built GP30s using the original flywheels, don't see any difference between them and a new Atlas GP30. They are all DCC and run just fine together even without speed matching. IMO the little extra flywheel weight is not going to make enough difference to offset the cost.
If all this is about making the loco's coast. I don't see the point. That is what your throttle is for. I never chop the throttle and let a loco coast to a stop. I've never seen an issue with an Atlas loco that makes it any less smooth starting or stopping than a Kato, although I don't have a large sample size as most of my equipment is steam. If it is about adding weight to the loco for traction, I fully understand. PS. The slow speed motors actually make more torque, they just don't draw as much current so it takes a little more voltage to get into their powerband. I've not seen a difference in pulling power between the motors at all. As Jim mentioned, I have transplanted motors both directions and have noticed no difference. If anything, the high speed Katos run out of power first becuase of their tall gearing but I have yet to see a diesel that stalls out the motor before spinning the wheels so its a mute point.
Reading the comments the only basic advantage I see is the added weight which should improve traction especially with dual flywheels. Only one issue comes to mind. That is that the flywheel needs to be precision centered on the shaft. With that I don't see any negative impact on the life of the bearing surfaces. Without that I can see excessive wear eventually on those surfaces resulting in some wobble and vibration and further wear.
The benefit I am looking for is twofold. I am looking for increased weight, and the flywheel effect will aid in situations where the lokie encounters a dirty area of track. I am well aware of the pitfalls and the accuracy required, and I can agree that the price will most likely turn most people off. I an working on a small fleet of GP units trying to increase performance. In the past, I purchased several pairs of Victor Miranda's re-geared trucks and was pleased with the results when I installed them. I hope to take advantage of the increased motor speed with the heavier flywheels. I have been playing with the concept of machining portions of the frame to take tungsten inserts, but the cost would be even harder to justify then the flywheels.
