Bachmann HHP Speed Performance Issues Under DCC and Solution

[mlrr]

Hello All,

Over the years I have regularly expressed my dissatisfaction with the max. speed performance of the HHP-8 locomotives and similarly the Acela Express train sets.

One remedy that seemed to work early on was bypassing the factory board from the decoder to the motor directly.  This improved things but then I noticed that this only helped the HHPs to max out around 80 MPH.

In recent month, 2/3 of my HHPs would mad out around 60 MPH (this is a big "No No" for NEC operations).  I've considered replacing the motors as an option as my experience working the Acela/NEC Layout at the Springfield shows for a number of years, Bachmann motors tend to show signs that they're on their last leg by dropping in max speed but I don't think my trains have run nearly as much as the Acelas on that layout (and at least mine would stop occasionally, lol).

I will say that I have found the cause of the problem and now they max out anywhere from 113 to 118 scale miles per hour.

So what's the culprit?

It turns out that the lucrative Back EMF feature of my TCS T1 decoders is responsible for the lower top speeds.  When disabled, there was a huge difference in performance.  But the down side is that the HHP-8s does not start smoothly and didn't start moving until speed step 30.  The remedy for this was adjusting the dither with CV 56 and CV 57.  The online manual walks you through how to adjust the dither so that your locomotive still performs similar to how it would with BEMF enabled.  See page 17 for how to adjust the dither.  The settings for my HHPs were CV57 = 165 and CV56 = 6.  You may also need to adjust your VStart, Vmid and Vmax.

Keep in mind that I also removed the capacitors on the circuit board.  On the first run of HHP-8s (650, 655 and 664) they are easily noticeable as these yellowish bulbs marked C1 through C4 on pc board.  Removing these will not affect the operation of your locomotive and were installed for the purposes of mitigating interference with televisions and cell phones due to international requirements (Bachmann is an international company after all).  Sometimes capacitors are mounted directly to the motor (as was found on one of my newer acela power cars).  Removing these capacitors does not void the warranty according to their website.

I haven't attempted this with my Acela power cars yet but they have the same decoders and I suspect they are contributing to their performance in the same way.

Thanks for taking the time to read this post.  I know I'm not the only one who have had this issue but I also know that there are few people online who can relate and contribute effectively to this issue (i.e. most chiming in don't model high speed passenger trains so you're more likely to get comments about running trains too fast than an actual solution).  As you can see, I had a bunch of well-intended suggestions but the solution was never suggested by anyone before.

With all that said, I'm a little less skeptical about the Bachmann Sound Value Amtrak ACS-64 that will be coming out next year knowing that there are actual remedies for this challenge.

[jonklein611]

I wonder if that's the same issue with my Bachmann J Class.

Thanks for the info!

[mlehman]

I narrowgauged 4 of the 70-tonners and none of them ran right until the caps were removed. These come with a control only decoder that's free, but pretty useless until the caps come off. They'd reset to default or weird values when rechecked, voodoo stuff. Eventually, I decided the free decoder wasn't worth the trouble and replaced it with NCE.

Then they run pretty good despite being hacked by me...I've learned to be a better 'surgeon' at each step, too. Hoping Bachmann upgrades this model like many others they done in recent years but retain the design that's easily modifiable. Better yet, why not a HOn3 version?

They could offer the 44-tonner as NG at the same time. IIRC last runs have all the same parts under the hood, just minor length differences in the chassis, so the same trucks should be usable on both.

[bdhicks]

Well, there are a few extra differences between the narrow gauge 70 tonner and the standard gauge model:
www.solrswat.ca/1%20Equipment%20Roster/Locomotives/1556/Locos%2029000%2029999/29296.htm

[mlehman]

Brian,
As the operator of about a dozen narrowgauge diesels, most of which came nowhere near Durango, I'm not as concerned about prototypical exactness as I am about acquiring additional motive power at a very reasonable cost.

The go-to book on the 70-tonners is: www.amazon.com/General-Electric-70-Ton-Diesel-Locomotives/dp/093074246X

GE built about 200 for the domestic market and another 200 for export. Most all of the domestic ones were standard gauge, while I know many of the export versions were narrowgauge, including meter gauge ones for Brazil. IIRC, there were some limits on the available traction motors that restricted fitting of them to units to under meter gauge, although there were some low amp choices. That likely accounts for the odd trucks on the New Mexico units. I rather doubt that was the standard trucks, in fact, there may not have even been a standard NG truck given the specialized nature of this loco. I don't have the book, maybe someone who does can give some additional insight?

Needless to say, this should not be seen as an obstacle to successful sales on HOn3 versions of Bachmann's light GEs. There's enough of a market for HOn3 these days that demand will support an almost-there model, given that there's a variety of other spotting features that would be just as "wrong" for certain variations as a set of B-B Hon3 trucks might be for the NM units.

Another possibility is to make both HOn3 and HOn30 versions, but that will likely require a new truck. As it is, most of the tooling for the current truck could be used for a HOn3 version, but is clearly too wide for HOn30. However, sales to the HOn30 crowd might be as lucrative as the HOn3 folks and the n30 segment is less worried about such prototype limitations than the n3 group is.

[bdhicks]

I do have that book, and as far as I can tell from it, all meter gauge and narrower 70 tonners used the C+C draft truck like the US Potash units.

I was being a little facetious though, since I'm pretty sure even if someone came out with a HOn3 (or HOn30) 70 tonner, the vast majority of buyers would not be getting them to model an obscure mine railroad.

A 4-axle narrowgauge unit might not be all that implausible. GE did allow a wide variety of customization, so I'm sure they would have made a 4-axle NG unit with the 70 body if asked (and somewhat did, in the form of 50-ton SP 1).


Still, I think the 6-axle draft truck version looks cool and I'd like to see someone make it.

[mlehman]

Jul 14, 2016 13:45:10 GMT -8 bdhicks said:

SNIP
Still, I think the 6-axle draft truck version looks cool and I'd like to see someone make it.

OK, that's good to know about the narrowgauge ones. Wish I could remember where I came across the info on traction motor size/width being a restrictive factor.

But I'd certainly buy a C-C HOn3 version. Even without a Cat engine in it, you could call it the "caterpillar" based on it's odd appearance.

As for lighter GEs, yeah, got a SP #1 slightly warmed over for Rio Grande service, a not implausible destination instead of Mexico. And the D&S has a pair of centercabs with the linked trucks (as I think the C-C ones were, too?) but are instead B-B that are ex-steel mill units. While looking a lot like a 44-tonner, they're likely heavier considering the original destination from GE. But IIRC, there were also some NG 44-tonners with very standard looking trucks (or at least more similar to the SG versions). The narrower, lower rated traction motors I'm remembering may have sufficed for the lighter unit.

[mlehman]

Had another thought on why B-B trucks may still be the way to go, besides possibly saving on tooling costs if current parts can still provide most of a HOn3 truck.

Both the 44- and 70-tonner are often narrowgauged, but the chassis, trucks, and drivetrain all commonly see use as the basis for various critters and railcars. For that purpose, the two-axle trucks makes much more sense.