Tsugawa Micro Motorized Chassis - Crawl Speed

[mags_minibuilds]

I've been using the Tsugawa TU-7T for one of my shortened B-Train Shorty trains. It really doesn't like to be ran at slow crawl speeds, it jerks tremendously. When I run it faster it seems to become smoother. I've tried adding weights but the same results. Whenever it passes a rail joint it slows down for a split second, it's super sensitive to the rails. Going backwards even at faster speeds it jerks. Is that the characteristic of these micro chassis from Tsugawa? Does it get better by running it more to "break it in"? What are your experiences?

[cteno4]

Always good to break it in with like 30 min running medium speed. Might check its lubrication status and if there are any binding points in the gears and such. What power supply are you using? Pwm power supply may make it run smoother at low speeds.

 

jeff

[mags_minibuilds]

I am using Kato Standard SX power pack on Kato tracks and a DIY PWM controller on 4 AA batteries on Tomix tracks. I added a tiny bit of lubrication and checked the gears and such. I ran it in both directions, slow and fast, for around 1 hour and I don't see any difference. It does rather poorly on points, lots of stalling. I have a brand new unit in the box and also a TU-9A unit that I tested and it has the same characteristics.

 

Here's the instructions, would it be due to the 3V motor? What does it mean by recommended operating voltage is 1V-3V? I can't get it to run smoothly until my power reaches 3.5V-5.5V.

 

 

Here are some videos, sorry for the background blur. Going backwards is consistently unstable. Going forwards, It has to hit a certain fast speed in order for it to become smooth. It's quite a bummer. I see that people on Shapeways has 3D bodies for these Tsugawa chassis, so I wanted to see if anyone had any tweaks before I completely give up on it and accept its disappointing performance.

 

 

 

Here's a YT video of the Tsugawa Koppel, the motor chassis looks very similar to the one I am testing. The video also shows jerkiness and stalling.

 

 

 

[cteno4]

Yeah tiny mechs are not the smoothest runners in general. The gearing resistance can start to overcome the torque of the tiny motors and hence easy to get some stutters. Of course this is worse with using lower voltage motors as lower voltage means lower energy per amp drawn. Also with lower voltage any tiny fluctuation in the circuit (ie contact with the track, dirty track) will have a greater effect on the motor, a 1v drop for an engine running at 7v isn’t much, but it’s a long for one running at 3v. Also the lower the voltage means you are now having the whole range of running for the engine only being a fraction of a 12v power supply so it will be a bit harder to finely control.

 

Not sure of how suited the motor is for this use as well. Some times for speciality mechs the motors are sourced may be designed for other purposes as they are readily available, but not great for a loco mech. T scale went thru this issue over many years as the first motors they used were something in stock for other uses and not great for a loco mech. They went and designed their own motor then and went thru 4 or 5 designs to get it optimized for use in a T scale loco mech. They also optimized their power pack for the best pwm control of the tiny motors.

 

Any little misalignment of gear axles can also just cause more drive train resistance at times and again harder for a small, lower voltage motor to keep running smoothly.
 

The tiny 2 axle wheelbase also will tend to make to hard to navigate point frogs cleanly and even hit points where electrical contact can be spotty so point always tend to be a jerky spot even for slightly bigger 3 axle switchers. Also the smaller the point usually the sharper the turn out radius and thus the more abrupt the frog angles and such so this can cause a little 2 axle mech to jump around a lot as it goes over it. Also with only the 4 wheels they will be more susceptible to any track gunk, so making sure track and wheels are clean helps (get some low dielectric contact cleaner to clean your tracks with, it works wonders for the black gunk)

 

As you noted, having little weight too it’s hard for the little mech not to jump around some and momentarily loos track contact, weight does help this. Also being two very close axles and light it can easily skew some on the track and that probably adds a tiny bit of stuttering as it will tend to bounce back and forth some. Being light it may also be slipping some at times. T scale mechs had this issue being so light the traction on the rail was so spotty it just didn’t work and why they ended up magnetizing the wheels and using a ferrous track so the wheels are sucked down on the track. 
 

So it’s going to be hard to get a tiny mech like this to run super smooth.

 

jeff

[Kingmeow]

I remember reading somewhere on the internet (here?) that they were not good runners due to poor pickup of the two axles, lightweight, etc.  I was looking into their duck series and thought it would be nice to DCC it and run it on T-Trak to amuse the kids.  In the end, based on what I read, I passed on the idea.

[brill27mcb]

Tramfabriek in the U.K. sells 12 volt replacement motors and converts Tsugawa drives with them:

https://tramfabriek.co.uk/

 

Notice that the motor is longer and makes the chassis higher overall. He's using it on HOe narrow gauge, so the height is not an issue for him. It probably is for you for a B-Train, but you will find other useful information on his website. You could also add a ceramic (?) resistor into one of the motor leads to increase the voltage necessary to run it and slow down its response, but be careful that the heat generated by the resistor  does not melt your chassis or body shell.

 

Rich K.

[cteno4]

Diodes in series (you have to do ones in both directions for each pole, so small pain there) is the old way of dropping voltage as each diode in series pulls about a volt or so each and not as much heat as a resistor might.

 

jeff

[brill27mcb]

Yes, diodes are a great way to drop the voltage that goes to the motor. Each diode (or twinned plus/minus-aligned pair in parallel) placed in series with the motor will drop the voltage the motor see by a uniform amount (about 0.7 volts). However, using diodes does not change the slope of a powered mechanism's graph of speed versus throttle voltage. The diodes simply shift the generally-linear performance curve to a higher, but still just as short, range of throttle voltages. So two diodes will shift the speed-voltage curve by 1.5 volts, but will not increase the throttle speed dial's range between slow and too fast. On the other hand, a resistor in series with the motor will do this, and then it's a matter of choosing the right wattage, resistance and type of resistor for the particular motor, and avoiding damage from the heat generated by the resistor. I have read posts on other forums from "critter" loco builders who use the Kato 11-105 type Shorty bogie chassis that they use a 100 ohm resistor to slow them down and improve the control range on the throttle dial.

 

You can read some of my vintage writing about trolley wiring methods in larger scales here:

http://www.eastpenn.org/articles/car-wire.pdf

Part 3 in particular shows how to use twinned diodes, and how to modify small-package bridge rectifiers to use them for space-saving voltage-dropping diodes.

 

Rich K.

 

[cteno4]

Rich,

 

eExcellent document! All my neurons on this are from way back as well. I do remember it being tricky to get the resistor value and wattage right to get the desired results and not too much heat output. I had a couple of switchers when I was young that I looked at trying to slow down, but with an n scale switcher there jsut wasn’t the room for the components.

 

jeff

[brill27mcb]

Fortunately these little cell phone technology motors draw very little current, so the heat generated by the resistor should be much lower than it was in days of old with larger, higher-current motors.

 

Rich K.

[cteno4]

Very good point!

 

jeff