Animated Monorail

 

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HO HIGH SPEED

 

*Really* high speed!  Like maybe 10x faster than the original, read on...

To start with, I don't consider the monorail speed to be a problem.  It seems about right to me, but what do I know?  I get maybe 1-2 emails a month from someone looking for a RC monorail and the first thing they ask for (after the cost) is more speed!  Well, after 40+ years of building slot cars I have learned a bit about electric motors and speed.

Some acknowledgements: the work done by "MonorailSilver" is incredible: his entirely new circuit board with a microcontroller is far beyond what I have done!  Others have also done some good work towards high speed: mostly faster motors and higher power batteries.  The various modifications have shown some improvements but the monorail has some big issues that really limit the speed and resolving those issues took a lot of engineering. 

Number one is the worm gears.  These are made for power, not speed, great for model trains.  Ever see a slot car with worm gears?  Yes, there were  few but they didn't win any races!  The monorail is geared about 42:1 with drive "wheels" about 11mm diameter.  Slot cars are geared about 4:1 with drive wheels about 20mm diameter.  To spare you the math that works out to about 20 times faster *before* a faster motor is factored in!

We may not need that kind of speed but 5-10 times faster might be nice, and we aren't going to get it by keeping the stock gearing and just putting in a faster motor.  The monorail needs a new drive system.  How much work is that?  A lot, but not impossible or even nearly impossible.  It's similar to scratch building a slot car chassis, something I have done a lot of.


130 size motors, the size used in the monorail, are plentiful and they come in several power ratings. Thanks to Kyosho mini-z race cars there are some seriously fast 130 motors but battery life is short.  By choosing a medium power motor and gearing somewhere between 8:1 to 12:1 we should have one fast monorail!

The stock drive "wheels" are the next big problem, a strange design but I can see why the designers chose them, ease of manufacturing (also known as cost). The wheels are actually truncated cones and ride on the angled sides of the beam.  Because of the shape they have a variable "gear" ratio and are always fighting themselves.  The new drive system has a nice round wheel that rides on top of the beam for fast, smooth power delivery.  The stock gearbox has to go, replaced by the new gearbox, gears, and drive wheel.  No other changes are required but adding radio control and a faster motor is a nice touch.  Btw, the new gearbox is designed to be a drop-in replacement for the original one, very little cutting to do on the plastic shell.

On to the batteries, a problem with the electric car and with our monorail.  Just as with electric cars, the faster we go the less time until we stop.  Some batteries have more capacity than others, the best NiMH are about 2500 mAH which should run even a fast motor for over an hour. I will not go into lithium cells, if we plan to use them we should understand the issues.

  Now for the modifications.  I normally would design something in CAD and have it 3D printed but I only plan to build one of these so it will be handbuilt.  I modeled the basic layout in CAD just to see how to fit it in.  If I get a lot of requests for this conversion (not likely) I will fully model it in CAD and make the 3D printed gearbox available online.  Or I might just sell this one.  ;)
The design actually branched out into two paths: keep the original motor and design a new gearbox and drive system; use a new motor with internal gears and design a new drive system.  Both of these are attached with the same screw locations used for the original gearbox!  The monorail chassis (lower shell) has to get a few holes cut out but it is nothing that is visible and nothing that prevents us from quickly returning it to the original drive system.

***One of the reasons I started this years ago is that each new monorail I bought was noisier and ran worse.  The gearbox and drive wheels were lower quality each time and the newest one barely ran at all until I replaced the poorly molded gears with better ones.  The conversion is much better and allows for different gearing to go from normal speed to 10 times as fast.

Instructions: Remove the gearbox.  Install the custom drivetrain.  Install the batteries.  Go.  That was easy!  Of course we can always add radio control and it is easier than ever thanks to the tiny Deltang receivers.



I went with about 9:1 gearing as a starting point, the ratio is easily changed later.  This is two sets of about 3:1 gears: one set of 9 and 29 tooth spur gears and a 9 tooth pinion with a 27 tooth crown gear.  The drive wheel is a 1/32 slot car wheel.  I kept the stock motor for now just to see how it performed (it was enough although I did buy a faster motor just in case). The stock motor can probably be geared higher for more speed. I do not have enough straight beam to test it but with a faster motor and higher gearing the speed can probably be doubled again!


Here is one of the drawings:

Sure, it's a lot easier to draw a high speed drivetrain than it is to build one.  I should know, here is the real thing.
bottom Not much different looking at the bottomtop

Plenty different inside!


But pretty drawings and cool gear systems still don't mean much, if it won't get from TTC to MK in 15 seconds what good is it?  Oh, but it will!  Check out the video, real time, not sped up...  About a scale 400 mph which puts it on a level with some fast maglev trains. The monorail will not stay on the beam for long so it is more than fast enough, and that is with the stock motor!

The video (25 MB):


So it looks good and the speed is unreal (or as Laurence Fishburne would say from the back seat of a Kia, "No, it is very real...".  So what does it cost?  Not much if you build it yourself, just some brass, gears, and bushings, batteries and charger, maybe $50.  As always I am up for helping anyone who wants to try building one of these.  I will provide parts lists; photos; and email assistance.


As for this project, I am done with it ( I sold it) because I don't have room for a layout long enough to use the speed and WhisperJet has all the speed that we can use with a lot less trouble.

 

 

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