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
Alton Junction
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
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
rrinker 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
50 MPH scale speed for an F3A passenger loco seems way too slow.
Top speed on the real thing was 100 MPH.
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.
- Douglas
One of my buddies wondered if the IM F3A locos are set up for freight operation, not passenger operation. Could that be?
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.
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.
rrinker Try turning the BEMF off on the DZ143, it will probably 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.
Try turning the BEMF off on the DZ143, it will probably 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.
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.
Wot Randy said.
http://exotic.railfan.net/F.htm
"One difference between pessimists and optimists is that while pessimists are more often right, optimists have far more fun."
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...
Hi-F drive, AKA rubber band drive.
Take Care!
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.
zstripeI 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...
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.
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.
rrinker 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.
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.
BMMECNYC 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.
Well if he was running a DCC decoder equiped loco on a DC power pack, I'm not surprised - that's just one reason I remove all those pesky decoders.....
The last thing I would do is start hacking up a perfectly good Intermoutain loco with different motors or gears - something else is wrong.......
The fact that Rich has two different top speeds from two locos that are identical except for the decoders, points in the obvious direction to me - that one variable seem like the likely cause - combined with my question above - what is the working track voltage of the DCC system?
12,500 RPM at what voltage? We still don't know that info?
ATLANTIC CENTRAL 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
Randy indicated earlier in this thread that more voltage would not produce more speed in DCC since the motor only draws so much current from the decoder.
ATLANTIC CENTRAL The fact that Rich has two different top speeds from two locos that are identical except for the decoders, points in the obvious direction to me - that one variable seem like the likely cause - combined with my question above - what is the working track voltage of the DCC system?
BMMECNYC My guess is IM assumes most customers will either run on layouts in a smaller space or run freights with Fs.
My guess is IM assumes most customers will either run on layouts in a smaller space or run freights with Fs.
Incidentally, my Athearn Genesis F3A's list "passenger" on the label on the box. So, Athearn does distinguish between passenger and freight locos.
richhotrain ATLANTIC CENTRAL 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 I have an NCE Power House Pro 5 amp DCC system. The voltage is steady at 13.6 volts, a reading of 13.2 volts with the loco under load. Randy indicated earlier in this thread that more voltage would not produce more speed in DCC since the motor only draws so much current from the decoder. Rich
I have an NCE Power House Pro 5 amp DCC system. The voltage is steady at 13.6 volts, a reading of 13.2 volts with the loco under load.
I'm not so sure about that. As long as the working limits of the circuit are not exceeded, more voltage should equal more speed.
Curent is a function of voltage and load, volts x amps = watts, more a function of the motor windings than a function of the decoder - that's why the wrong motor will fry a decoder that cannot handle enough current.....
I wonder what voltage the power supplies of other DCC systems are. I remember hearing numbers as high as 16 volts with Digitrax.....I could be wrong. 13.6 seems low considering it is AC and needs to rectified in the decoder. A diode bridge (rectifier) is easily a 2 volt loss......11 volts to the motor, plus losses in the factory lighting board before the decoder, no wonder the locos run slow.
Again, I'm not a DCC expert, but I will aska few if I get a chance.
NCE states that the 5 amp system is factory pre-set at 13.8 volts, but it is adjustable.
ATLANTIC CENTRAL I wonder what voltage the power supplies of other DCC systems are. I remember hearing numbers as high as 16 volts with Digitrax.....I could be wrong. 13.6 seems low considering it is AC and needs to rectified in the decoder. A diode bridge (rectifier) is easily a 2 volt loss......11 volts to the motor, plus losses in the factory lighting board before the decoder, no wonder the locos run slow.
Sheldon,
Here are the specs from the Walthers website.
Flat Can Motor 12VDC 16 x 27mm, Double Shaft 1.5mm Dia. x 9.5mm, 12,500rpm (Repl. #122719) Walthers Part # 53-1627D9A scale,$24.95, currently in stock at Walthers
Edit:
The RMS value of NMRA digital signal, measured at the track, shall not exceed by more than 2 volts the voltage specified in standard S9 for the applicable scale.
S-9 states 12Volts minimum
From RP-9:
Powered equipment shall operate at a speed within 25 percent of their nominal maximum prototype speed divided by the appropriate scale factor (See STANDARD S-1) under the following conditions:
The input voltage shall be the minimum voltage stated in Section I A of STANDARD S-9. The unit running "light" after a run in and lubrication according to the manufacturer's instructions, on level, tangent track laid at minimum gage.
richhotrain 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
Did the tech indicate in any way that he knew that the IM locos are designed to run at a slower top speed?
It sounds like IM is not aware of what top speed they designed the loco to run if they can't tell you why it runs slower. Maybe they didn't design-in any particular top speed.
Just speciulating.....Weren't the IM F units originally designed to fit over Stewart chassis? I'm thinking maybe the gear ratio is just left over from parts/design of that chassis...that when they upgrade the electronics and price of the locomotive, they didn't redesign the entire drivetrain but used the same chassis/drivetrains that were being supplied to/by Stewart...which may have been based on frieght loco gearing.
Whereas the locos you are comparing them too were designed fromt he ground up to perform more like the prototype.
I never tried to accurately measure them, but I'm pretty sure my Stewart FT and F3's don;t run 80+mph at full throttle.
The thing here is the difference between the IM and Athearn on DCC, which does not appear to exist on DC based on Sheldon's results. Unless IM changed gear ratios in different releases. There's a difference in decoders, but outside of some known things, like Digitrax reserving some of the top end for BEMF speed control to work - which is why disabling BEMF on the Digitrax decoder brought the speed of the two IM units into alignment, there's really no reason for it. The details vary, but all decoders work pretty much the same, there's a bridge rectifier and then an H bridge driven by PWM to control the motor. The pulse amplitude is going to be the track voltage less a few diode drops (in the rectifier and in the drive transistors in the H bridge). So a decoder loco with a DCC track voltage of 13.5 volts will be slower then the same loco with no decoder and running on DC that peaks at 13.5 volts. But here we have the Athearn unit just as fast on DCC as it is on DC. Only the IM units have a problem. As for system differences, Digitrax's larger systems all have a scale switch to set track voltage, the HO setting is about 15 volts, the N scale is about 12 volts (assuming you use a proper power supply). On their starter systems, Zephyr and Zephyr Xtra, they don;t have thise setting and the voltage is fixed at around 13 volts to be suitable for both scales. NCE does similar with the PowerCab, one less setting to worry about for the beginner. Because of the drops in the decoders, this will usually result in a slightly lower top speed than the same loco without a decoder on a standard DC power supply. The slightly higher HO setting on the bigger Digitrax systems compensates for the losses in the decoder so the motor gets to full speed.
More voltage will equal faster speed, but the most you really want with HO is about 15 volts on DCC. For large scale, which often has motors that run on more than 12 volts, it's more like 20-22 volts DCC.