# Bachmann Railtruck conversion to Airwire, Zimo decoder and battery power



## Beddhist (Dec 17, 2013)

This is a first for me. I have never worked with any of the components. In fact, I am new to large scale and train electronics.

To start with, I dismantled most of the truck to fix the known gear box problem, as per http://www.girr.org/girr/tips/tips8...ml#gearbox There is play in all the drivetrain components, so I wonder whether the diff will cause problems in the future. Lots of loose screws in the chassis were tightened.

Here is the chassis with all the gadgets that must be installed:

http://www.gscalecentral.net/index.php?action=dlattach;topic=298175.0;attach=177907;image

There is an Airwire Convrtr, a Zimo MX645 with the Galloping Goose sound preloaded and an ESU speaker. The battery is only for testing and will be replaced by something more compact later.

First step is to lose the circuit board. I simply cut off all the wires. I cut the pickup wires to the rear wheels flush with the deck. The speaker will probably sit over the slots in the centre, but there are some burrs from manufacture. 4 screws and the rear axle comes off, I then removed the pickups and everything that went with it. The burrs could now be removed with a sharp knife, so they won't interfere with the speaker.

Next was a lot of wire stripping and soldering, a process made a little difficult because of my poor eye sight at close range, plus my fingers are not the most nimble. At this stage I didn't wire the lights, as I don't have any resistors on hand. After triple-checking all my connections I connected the battery and fired up the Tx. Result:

http://www.youtube.com/v/0DOo88okj6o&rel=1&fs=1

Hooray, no magic smoke and it works at the first try. First impressions: this is hard to control! Most of the time when I hit the stop button it just keeps going. Most of the time it ran off the end of the track. Sometimes pressing one function key activates the next numbered function. Most annoyingly, after pressing a function key you have to wait several secs before you can use another key. If you don't it is ignored. For example, you can't sound the horn twice quickly. At slow speed it runs jerkily. I don't know whether this might improve over time.

Next is wiring the lights and then installing it all permanently, as well as re-assembling the truck.

Regards,
Peter.


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## Dan Pierce (Jan 2, 2008)

Most DCC systems have acceleration and de-acceleration CV's for engines and may need to be changed.
Look at CV 3 and 4 for this in the MX645 and in the airwire.


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## Beddhist (Dec 17, 2013)

Thanks, I know what you mean. The momentum is probably where it should be for actual operation on a track. I would not normally zoom into a siding at silly speeds, but for testing... 

It's the function buttons that I find annoying: I often have to press them twice, as there seems to be a timeout that has to elapse before you can use a button again. So, for example, you can't give two short whistles rapidly, they have to be about 2 secs apart. Also, you can't do a long whistle at all, the time is fixed. 

Interesting, I just tried running it on 24V. The motor didn't like running on speed 3 and 4. With the momentum as programmed that makes taking off almost impossible. On the other hand, once I got the speed up it ran a lot faster. Back to 12V and it runs like before. The Convrtr is rated at 28V and the Zimo 35V, so I didn't expect any problem here. 

There is always the possibility that my jury-rigged batteries or one of my solder joints doesn't handle the current. 

As I lost control one more time and I did an emergency stop using my hand as buffer it spat out the drive shaft. I took the diff apart and found that the pinion gear has a brass bearing, which is very lose in the housing. I shimmed it out with a couple of bits of insulation tape and now it has almost no play. Most of the remaining play is now in the gear box and the excessive motor end float. The universal joints are press fits, so no play at all here, nice and simple.


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## East Broad Top (Dec 29, 2007)

Is the slow speed issues something like a stuttering motion or similar? And it goes away at higher speeds? That sounds akin to BEMF motor control settings not being tweaked properly. I don't use Zimo decoders, so I don't know how much control you have over that or how to tell you to adjust it. Look in the manual for "PI" or "PID" control or something like that. Unfortunately, making adjustments to this to get smooth operation is seldom as easy as "turn this one down a bit to smooth things out." You may have to do a search online to find various settings others have used successfully and try those. Zimo may have them on their site. You may also be able to turn off BEMF throttle control depending on the decoder. 

In terms of the deceleration, check to see if the Zimo decoder has a prototypical braking feature that may be turned on. The QSI and Tsunami decoders I use have this; you've got to use one of the function keys to actually slow down as you would if you were to apply the brake on the prototype. It's fun to run like that, but definitely takes some getting used to.

Also, set your max speed CV (CV5) to something about halfway and see how that improves performance. Geese didn't go very fast, so at full throttle, you probably want your speed to be around 30, 40 scale miles per hour. Of course, how that control works will be dependent on the voltage you're sending it, since it's a proportional setting (i.e., 50%, 70%, etc). I would bet that you could get away with an 11.1 v. Li-Ion pack in this one and have plenty of speed available. The Convertr and Zimo should both work well at that voltage.

Later,

K


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## Beddhist (Dec 17, 2013)

Thanks K, yes, stuttering is probably a good description. I don't recall whether it did that on 24V only or at 12V as well. When I said that it didn't like running on 3 or 4 I meant that the engine actually stops altogether, even if I turn the power up. On 24V it is unusable.

I guess I take your advice and stick with 12V (or 11.1). I know that works.

The sound is quite nice. As the speed increases there are actually gear changes. F9 in the docs says "chain". I'm not sure what that is supposed to be, but it does sound like the driver has just dropped the anchor!

Oh yes, it also says that I have to do a calibration run. Apparently I set CV302=75 and it will run for 5 m to calibrate the engine control. I have yet to do that.

Now, this 24V problem has me worried for my Davenport, as that will draw a little more current and will have to pull a few wagons.

Stay tuned!

Regards,
Peter.


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## Dan Pierce (Jan 2, 2008)

There are CV's to be changed for BEMF on the Zimo decoders, 
Look at page 16 to 20 of the MX620, .... manual for tweaking the Bemf.
And CV57 has absolute voltage to the motor so you can keep your system at 24 volts and limit the motor to any voltage you want, not a percentage.
Also, check your speed steps, make sure your both the airwire and Zimo (CV29) are set to the same value.


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## Beddhist (Dec 17, 2013)

How do I find the actual CV settings in the Zimo? AFAIK Airwire will not read CVs and I have not yet found what settings are changed in the sound project. The default values will be in the manual, no doubt. I have downloaded the project file from Zimo and I guess I have to install their program and load the project into that. I expect that I will see the defaults that way.

Again, thank you all for your help.


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## Dan Pierce (Jan 2, 2008)

When you load a project, the default values in the manual will be different in the project loaded..
My system will read CV's so I know what they are before I change them.
And my software will store the CV's so I can reload them.


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