I think that my Intermountain F3A locos run rtoo slow. Not sure if it is the chassis, the gear ratio, or the decoder. So, I ran some speed tests. Here are the results.
Intermountain F3A - After market decoder, Digitrax DZ143PS. 51 MPH.
Intermountain F3A - Factory installed decoder, QSI. 58 MPH.
Athearn Genesis F3A - Factory installed decoder, Tsunami. 79 MPH.
Thoughts?
Rich
Decoder differences between the two Intermountains. Different gear ratio than the Athearn, or just different motor speed.
50mph is plenty fast for a freight train.
–Randy
So, which is it? Different gear ratios? Different motor speed? Is the 1 amp Z scale decoder to blame?
50 MPH scale speed for an F3A passenger loco seems way too slow.
Top speed on the real thing was 100 MPH.
Rich
Any chance that you can pop out the decoders and temporarily direct wire the truck wires to the motor leads and test them on DC? At least you’d know that the same amount of current was getting to each motor.
One of my buddies wondered if the IM F3A locos are set up for freight operation, not passenger operation. Could that be?
Rich
Have to fit an Athearn motor to an Intermountain or vice versa to see if it’s just motor RPM differences. More likely the gear ratios are different though. As long as the motor doesn;t draw more current than the decoder can supply, it doesn;t matter if it’s a 1 amp decoder or a 3 amp decoder. That would make no speed different at all. Try turning the BEMF off on the DZ143, it will probbaly be closer to the other Intermountain - Digitrax seems to ‘reserve’ a bit of power at full throttle so that there’s more to give if the loco slows down with a heavier load. With BEMF off, full throttle will really be full throttle. Like the Proto E units, not fixable without replacing the gearing. A different decoder would only change the speed a couple of mph either way, not magically make one that goes 51mph suddenly go 90.
–Randy
I did a bunch of speed matching for a fiend friend, including Atlas and Athearn locos, and found that the Atlas units were about 85 smph while the Athearns frequently topped 100. I’m sure that different motors/gearing can make a difference.
Randy, great suggestion. Turning off the BEMF shaved 25 seconds off the run around the 180 foot mainline. Cut it down from 3:29 to 3:04, nearly indentical to the IM with QSI decoder. CV57 was set to a value of 6, and I cleared it to zero.
Incidentally, the Genesis F3A with the Tsunami decoder makes it around the layout in 2:15.
Rich
Yes, IM probably considers them freight locos, so 50 is good for a model, even though the real things were likely geared to around 65 for freight use. According to one source, the max gearing was good to 102, the slowest version allowed a speed of 50mph, with a LOT higher tractive effort than the 102mph gearing, although it also said the most common options were between those extremes.
–Randy
I still have a couple Athearn Hi-F drive A’s laying around, that will accept Your shells…they are good for a good 200+SMPH…[swg]
Hi-F drive, AKA rubber band drive.
Take Care! [:D]
Frank
I will try to run a speed test on my DC versions tonight - my max track voltage is 13.8, filtered DC.
If I recall, mine do run faster than 50 smph at my 13.8 volts.
And I have both Genesis and Intermountain units handy to test…as well as a measured length of track and a stop watch.
Sheldon
Sheldon, I will be most interested in your results.
Rich
I think my daughter’s will top that. [:)] Made for a Youth in Model Railroading locomotive drag race. We put in a high speed slot car motor and added thicker drive shafts so the “gear” ratio is reduced. It could have run the track 4 times, while a Hustler with standard motor and rubber band drive (my son’s entry) was doing it once.
Seriously, while not mentioned in the locomotives being compared on this thread, I’ve been disappointed with Walthers Proto line and their “standard” 14:1 gear ratio for passenger trains. I get about 79 mph out of then. Totally unacceptable for the Super Chief, El Capitan, their tribesmen, not to mention the Empire Builder and Hiawatha. sigh. Granted most people don’t have the space for those speeds but we try to be prototypical in everything else.
Rich,
DC speed test results.
Conditions:
Straight level track - somewhat dirty
Aristo Train Engineer throttle - set to pulse width modulation mode
Input voltage to Train Engineer Throttle - 13.8 filtered/regulated DC
Max voltage at rails under load - all test subjects - 13.2 to 13.4 volts
Locos running free - no cars
All units a straight DC with no decoders. All have factory lighting circuit boards.
RESULTS:
Intermountain F3 - several different locos - 75 smph
Genesis F7 - several different locos - 80 smph
Intermountain FP7 (newer producton than the F3’s tested) - 72 smph
Early Proto E8 - 83 smph
Early Proto FA1 - 72 smph
Notes:
The Intermountain and Genesis units ran well MU’d together averaging out their speed at about 75-77 smph.
Keep in mind, most “normal” DC power packs put out higher voltages than my regulated 13.8 volt power supplies.
All locos were given some warm up time and multiple tests, but they have been sitting in my train room which is only heated when I go up there - above my detached garage.
Ambient temperature during tests, about 60 degrees.
Since 12 volts is still considered the full throttle minimum standard for DC, all of these models reached reasonable fulll throttle speeds, even if they did not match prototype maximum speeds exactly.
I’m sure another volt or two would push them all to the 90-100 smph range.
Still sounds like a decoder problem to me.
Personally I like the idea of the full throttle setting being somewhere close to the expected full speed you would actually use - it allows the full range of the throttle to come into play while operating the loco.
Sheldon
That’s pretty odd though that the Genesis on DC ran SLOWER than on DCC. But the Genesis were close, even with a decoder, to the DC version, and the Intermountain is way off. Unless the Intermountains have CV5 set to non-zero to limit top speed.
–Randy
???
My Genesis F units ran 80 smph at only 13.3 volts pulse modulated DC.
Rich tested his DCC Genesis unit at 79 smph.
I spoke to a technician at Intermountain yesterday about the scale speed issue with my F3 locos. He ruled out the decoder or the motor as the cause. He did agree that turning off BEMF would help a little, but felt that the gear ratio was the source of the “problem”. However, he did not feel that the gear ratio was a problem in general, and he indicated that changing out the gears would not be practical or even recommended.
Rich
Would it be possible to aquire a higher speed motor of similar size? If this was a larger locomotive I would suggest a possible step up gearing (add a large gear on motor shaft, meshing with a small gear on the worm shaft) to give an increase in speed, but I doubt you have space in an IM F unit for that. My guess is IM assumes most customers will either run on layouts in a smaller space or run freights with Fs.
And a similar experiance with unsatisfactory top speeds:
I was at a hobby shop near Boston, MA a couple years ago and was looking at buying a Bachmann Spectrum J. Fortuneately for me the guy working the HO scale counter (they have separate counters for different scales, have to segregate the 3 rail folks from 2 rail, otherwise you end up with arguments and name calling!) volunteered to run it on their 10ft test track. Time from one end to the other: >20 sec at max throttle setting. He could tell that I was no longer interested in purchasing it and boxed it back up and set it in a cardboard box on the floor behind the counter for shipment back to Bachmann.
Edit: NWSL has one that spins at 12,500rpm. Dont know what IM uses. Available on walthers for $25.
I’m not a DCC “expert” so I will ask, does track voltage effect maximum output voltage to the motor? I would think so.
So Rich, what is your track voltage?
Does this vary from brand to brand? is it adjustable in any way?
Higher voltage should provide a higher top speed…at least with DC.
My Intermountian locos run 20% faster on DC than what Rich records on DCC - seems like a big drop - and again, I’m using 13.8 volts, 13.2 volts under load.
Most DC power packs put out more than my 13.2 volts.
As soon as I have time, i’m going to run some tests with several MRC packs I hove on hand - and, I can actually increase my regular power supllies by about one volt - might tes tthat as well.
Sheldon
