Gearing

[nkp174]

I've assembled the frame (or at least ver 1.1) of my 2-8-0 project. Now I need to get it powered.

I've decided on a coreless motor...haven't decided if it will be a Maxon or a Faulhaber...whatever I get a good deal on. (I am very well versed on the pros and cons of coreless motors and have NO interest in can motors.) I'm inclined to stay away from CD-rom motors for this...it's going to be a 3lb locomotive and I doubt they have adequate torque for the kind of pulling this baby will be used for.

The big question is gearing. I hate worm gears...hate them. So, there goes the two top suppliers of gearboxes on my list: NWSL and PSC.

Grandt Line offers bevel gears and pinions...they are tempting for they allow me to hide the transmission (a big eye sore to me). My Grandt Line porter has this type, along with a Maxon 2020, and I love it. I'm not adverse to making my own gearbox. At around $10 for Grandt's sets...they are far easier on my budget than a $40 job from NWSL or PSC.

I've also thought about a belt drive. I recall seeing that Ray M. had used them with good results before.

An additional option I might consider is pulling the blind #2 drivers off of the geared axle and moving it to the #4 position so that a normal gearbox could be used and hidden in the firebox...with the motor facing the opposite direction of a normal model...but then she'll still have a worm gear :-(

This is an On3 locomotive...so it has slightly more space in the frame than an HO locomotive.

Any alternative options? Any good British cottage industry solutions that won't break my budget?

Thanks

 

[pgandw]

Hobbytown of Boston used to use helical gears in their diesel drives. Helical gears can be used as spur gears for parallel shafts, or at 90 degrees like worm and worm gear. Because the teeth are not straight, they are quieter than spur gears, or crown and pinion gears. Drawbacks are the reduction ratios are not as great as worm drives, and the sliding action of the gear teeth imparts an axial thrust that must be countered by good bearings. I believe Mirco Mark bought up the Hobbytown of Boston stock after the 2nd owner, Bear Locomotive Works, gave up. I think Grandt may some helical gears, also. Grandt also has their plastic chain drives, which might fit.

Problem areas I see with your plan:

Coreless motors have very high RPMs and low torque when compared to other motor types. The torque and RPM become adequate with sufficient gear reduction. Typically a gear head is mounted directly to the motor for an initial reduction. Gear heads can be noisy (straight spur gears) if operated at high RPM. I have heard of using 24 volt coreless motors to get around some of these issues.

If you use a very smooth drive, you can have a runaway locomotive on a steep downgrade with a load behind it. This very seldom happens with a single thread worm setup, but is possible. With other drive setups, being able to reverse drive the motor is more in the realm of possibility. If the drive is free enough that you can cause the motor to turn by pushing the locomotive on its wheels, then there is a downgrade (usually fairly steep - on the order of 6% or more) at which point the locomotive will free wheel, reverse driving the motor. At this point, you can no longer stop the train by simply zeroing the voltage. Without a sophisticated control system, you have a run away. :cry: I learned this with my Lionel trains, believe it or not.

just some thoughts