Model Railroad Speedometers

We now offer a choice of methods to see the speed of your model railway.
There is an option to drop into your - or your friends' - layout, and see at a glance how fast those speeding trains are really going.
Alternatively, build in the speed sensors and bring the display to your front panel.
There is also a choice for setting up each loco, aiding in start and to speed setting, speed matching and forward and reverse balance.

ACCUTRACK II Speedometer

Accutrack Speedometer

Have you ever wanted to know the scale speed that your trains are achieving as they run round your layout?
Now you can do so, easily, with our layout Model Railroad Speedometer.
Programmable from the front panel for N or HO, miles or kilometers this unit stands over any track,
and displays the correct scale speed of a train as it passes, in either direction.
Suitable for DC or DCC, the unit runs from two AAA batteries (included) and has auto power off when not in use.

This easy to use ACCUTRACK II Speedometer is available from our online store.
Now supporting US (1:160) and UK (1:148) N scales, H0 and 00, all in scale miles or kilometers per hour,
this unit stands over any track, and displays the speed of a train as it passes, in either direction.
It is a stand-alone device, and runs off two AAA batteries, included in the package, so is ideal for DC or DCC layouts.

The "tunnel" is large enough to straddle two N tracks, or one H0 track, and is tall enough for double-stack containers. Speedo
Seen here measuring 38 MPH for this N Scale freight train.

See our Application Note for using this Speedometer to help set up speed-matching of locos with SPROG.
Click here to order your Accutrack Model Railroad Speedometer.



Trainspeed 1, built in speed measurement

Trainspeed

The Trainspeed system is designed to measure the scale speed of your trains as they pass by sensors placed at a specificed distance apart.
Two small light sensors are set into the track, and as the train passes over, the Trainspeed system calculates the time taken, and so the speed of the train.
By placing the sensors at the right spacing, this system can be set up for any scale.
The sensors are designed to use available ambient light. It is best to pick a well lit section of the layout where the light source comes from above and ‘inside’ the layout.
The Trainspeed 1 package includes everything that you need to build in speed measurement at your chosen location, including 2 sensors, cable (10 feet in total length) and control/display module. Power can come from any accessory supply 6V-18V AC or DC, or purchase our 12V supply.
See the full manual for more information about installation and setup.
Click here to order your Trainspeed speedometer kit.



Bachrus Speedometer

Bachrus Speedometer

We also offer the Bachrus DCC speedometer, available in N or HO scales, which is ideal for setting up and speed matching locos on the programming track, in conjunction with your SPROG (or other DCC system), computer and DecoderPro.
The Bachrus system is based on a "rolling road" concept. Supplied with sufficient rollers and rails to support 8 powered axles (think articulated steam, or big diesels) and a tender or other unpowered wheels, these are ideal complements to your loco setup environment.
See more information, including videos at the Bachrus site.
Click here to order your Bachrus Speedometer set.


Some hints and tips about speed matching

With acknowledgement to Dave Heap for these details and recommendations

- The NMRA S9.2.2 specifies that all decoders must provide CV2 (Vstart).
The provision of CV6 (Vhigh) and CV5 (Vhigh) is optional. These three CVs are to be active only when Bit 4 of CV29 is 0.
Speed tables are optional and use CVs 66 (Fwd Trim) 67-94 (the actual speed curve) and 95 (Rev Trim).
These thirty CVs are to be active only when Bit 4 of CV29 is 1.
The disadvantage of this speed table specification is that any tweaking of starting or maximum speeds requires reshaping of the entire speed curve.

- SoundTraxx Tsunami decoders differ from the standard.
When the speed table is active (Bit 4 of CV29 is 1), the value in CV2 is not ignored but is effectively (in the decoder)
added to CVs 67-94 in the speed table, pushing it upwards.
The advantage of this variation from the NMRA standard is that you can tweak the starting speed without reshaping the whole curve,
but the disadvantage is that you can effectively flatten the top end of the speed table it the maximum speed was already high.

- QSI decoders differ from the standard.
When the speed table is active (Bit 4 of CV29 is 1), the values in CVs 2 and 5 are not ignored.
If either of CVs 2 or 5 are non-zero, these become the actual Vstart and/or Vhigh
and the effective values in CVs 67-94 are compressed or expanded (scaled) in the decoder
so the actual curve starts and/or ends on any non-zero value in Vstart and/or Vhigh.
The advantage of this variation from the NMRA standard is that you can tweak both starting and maximum speeds
without reshaping the whole curve, but the disadvantage is that if your speed table already covered a restricted range,
the curve will be expanded, with possible integer multiplication errors producing glitches in the speed table.

- ESU V4 and Select decoders differ from the standard.
When the speed table is active (Bit 4 of CV29 is 1), the values in CVs 2 and 5 are not ignored, but ALWAYS specify the actual Vstart and Vhigh of the loco.
In addition the value of CV67 is fixed (read only) at 1 and the value of CV94 is fixed (read only) at 255.
You therefore need to fit your speed table curve shape between these fixed end points.
The effective values in CVs 67-94 are compressed (in the decoder) so the actual curve always starts and ends on the values in Vstart and Vhigh.
The advantage of this variation from the NMRA standard is that you can tweak both starting and maximum speeds
without reshaping the whole curve and without the possible multiplicative errors in the QSI approach.
The LokProgrammer and JMRI DecoderPro software both enforce the restrictions on CVs 67 and 94 so you know what your speed table will actually look like.
Also, the minimum value for CV2 is 1, so you cannot set the loco to be stationary at step 1.

The important thing to make very clear is that ALL FOUR DIFFERENT APPROACHES ALLOW FULL CONTROL OF SETTING THE ENTIRE SPEED RANGE OF THE LOCO.
There is no limitation on setting of starting or maximum speed. But you MUST be aware of the different ways of setting up different decoders.
The other important point is that THIS DOES NOT PREVENT SPEED MATCHING of different brands, you just have to be aware of the different ways of setting up each brand.

The best way of avoiding problems is with any brand or mix thereof is to match speed steps in this order 1,28,14,7,21,... This will avoid any problems with any brand.

About Us

We are the BBM Group LLC, a family business specializing in solutions for model railroaders.
Model railroads come in many sizes, and we specialize in N Scale, with a track gauge of Nine millimetres.

Contact us for more information, and to share your ideas and needs.