does anyone know where to get AC motors for modeling. I want to convert my SD70MAC into a real AC locomotive.
I see you live in AU, so before I can answer that I need to know if the water swirls clockwise or anticlockwise in your toliet?
Why would you want to do that?
flee307: the toilet water does not go clockwise or anticlockwise, it flushes.
billkamery: my DCC system like everyone elses uses AC. the locomotive picks it up and the decoder sends it indirectly to the motor by making the AC more like DC. i want to find a way to make my decoders supply the AC directly as AC. the motors would be mounted on the axles and that would leave room for sound systems and interiors. i want to have a sound system in my SD70MAC but superdetail it and make the side doors open revealing a veiw of the inside fully mdeled interior.
The way you decribe dcc and ac is incorrect. Most past and current DCC stations will run on 16 VAC or 18 VDC. The DCC station converts the AC or DC to pulsed DC and the decoders apply a chopped section of this pulse to the motor as pulsed DC as told to it by the signal which is multiplexed on the line with the pulsed DC.
ive been it the indusrial electric motor repair business for 15 yrs…ac motors run at a constant speed depending on how they are manufactured…typically 900,1800, or 3600 rpm constant…dc motors are designed to change speed by vaying the voltage to them…ac motors can only tolerate a 10% variation in rated voltage…plus this does nothing to change its speed…(unless u let it run to long this way and then it will burn up and stop…speed change accomplished)…aside from attaching a gearbox to ur ac motor…dc is the only way to go…its used in rc cars, boats,trains of all sizes…scott
Ive done it before with the motors mounted on the axles but forgot which company made the motors.
Don’t do this.
Seriously, fitting motors inside the trucks will result in very odd gearing, possible problems with synchronising the motors, etc, etc. In the UK we’ve only just started to get away from truck-mounted mechanisms and into decent US-style drive systems, There is little or no space for the gearing you will need to avoid problems with slow running and excessive top speeds. Also, I find it hard to believe that axle-mounted motors (In HO scale anyway) would be able to generate enough torque to move a decent length train. I’m also a little puzzled as to why you would want to model the interior - to the best of my knowledge locos never run with their side doors open, and a static “loco under repair” could be better represented with a cheap dummy loco.
slossmo says, “ive been it the indusrial electric motor repair business for 15 yrs…ac motors run at a constant speed depending on how they are manufactured…typically 900,1800, or 3600 rpm constant…”
That’s not true, brushed AC motors have been used for years to power among other things sewing machines. I know that they will run from almost 0 rpm to well over 10,000 rpm depening on the voltage being sent by the footpedal which is just a big resistor. We also have frequency controlles on our three phase motors and they will run from near zero to max rating or anywhere between. What about ceiling fans, they have 3 speeds built in ususally and also can be speed up and slowed down with a motor “dimmer switch” . They are AC inductive motors. Todays state of the art locos use AC traction motors and they seem to be able to run different speeds without burning up. The only reason they used DC traction motors for years was know one could figure out how to make an AC controller big enough to control the current required to run 4000 hp locomotives. So what’s the deal with your statement?
Not to mention the obvious. Marklin & Lionel AC.
However, the track voltage for DCC is actually pulsed DC, not AC, and an inverter is big & heavy.
I seem to recall that years and years ago American Flyer had some HO which might have been AC. That was back when DC motors were usually 6 volt. Before my time actually.
Anyway as to mounting motors on the axles that should work and there was a product called the SPUD which could do this. It was a small DC motor with, I think, the axle shaft also part of the motor shaft.
That way for example a tunnel motor could actually have a see-through rear vent, and trolleys could have detailed interiors. But if each axle was a motor I do not know about current draw and frankly I do not know if I ever saw an article on converting SPUDs to DCC for that matter.
Dave Nelson
see the digitrax web site appnote at http://www.digitrax.com/faqdt.htm
DCC is AC data pulses, the decoder has a rectifier and pulse modulator to convert the AC data packets to controlled DC pulses for the motor. If AC is applied directly to an AC motor, it could not run in reverse unless the field winding is reversed; DC motors use permanent magnets instead so they can be made smaller. Also the drive gearing allows a lot more low speed torque to be applied to the wheels with the motor running at a higher speed, kinda like first gear in a car. Direct drive would lose all this torque.
I had an American Flyer S scale as a kid, it must have been AC powered since to reverse one had to fully stop the train, then apply power again to cause a stepping relay in the tender to swap field winding polarity. Then re-apply power to run in reverse; repeating the sequence would set it to forward again. That was in the days before silicon diodes were available and the usual selenium type rectifier had way too much resistance for low voltage, so AC and a variable turns ratio transformer was the only way to go other than batteries and rheostat. But they still geared the motor down.
PS Mine all swirl counterclockwise. Is that correct for the Northern hemisphere? If not that Coriolis force thing just got debunked.
AC is a sign wave. DCC is pulsed DC that has a positive and negative component that is phase shifted. It’s like a pulsed DC power pack that has pos and neg leads and ground. The pos is +12v from ground, the neg is -12v from ground, and they are 24v apart from each other. But they are still DC.
Maybe someday the makers of model trains will incorporate Alternating Current type motors into our “toys”. The technology to control their speed/torque does exist (I’ve been working with it for 20 years) but I’ve yet to hear of it in model trains.
If more than one motor were to be fitted into each loco, synchronization should not be a problem. AC motor speed can be regulated by utilizing “variable frequency control”. If all motors are running from the same current source they will be synchronized.
Keep wishing for that to come about. No more brushes!
Brush problems? Do you really have brush problems? I have never replaced a set to date.
Now we get into similarities and differences between these terms, and pulsed DC and AC can look very similar. AC is not necessarily sine wave, any waveform (including rectangular pulses) that is one polarity for 1/2 its cycle and then reverses polarity for the other 1/2 cycle is AC. This is the type of pulses used for LANs (Ethernet etc) and is chosen so it will pass through transformers at computer interfaces without distortion. Pulsed DC alternates between one polarity only, then completely off, and has an average DC value that makes DC motors run in one or the other direction. DC pulses can also be sine shaped (MRC power packs) as well as square. It is also the type of signalling used for digital logic (TTL, CMOS etc) that does not have to pass through transformers. The bridge rectifier in a DCC decoder converts the AC pulses to DC to operate the decoder logic.
But a 50% pulsed DC wave will pass through a capacitor with some distortion, and if no DC offset is added afterwards it becomes AC since it becomes centered about 0 volts and has true positive and negative reversals. If a DC offset is added it stays pulsed DC. If it is not 50% duty cycle, it becomes AC with a DC offset (one polarity is a higher voltage than the other) so in effect it becomes both together.
The main difference between AC and DC is that if you filter pulsed DC with a large capacitor, you will still get a DC voltage at the average value of the pulses. But if you filter AC the same way, you get 0 volts.
If you look at AC or DC pulses on an oscilloscope they can look identical. The only way to know what you are seei
Actually, the water does go down counterclockwise, and then gets shot back out again when one of us yanks flushes up here on top of the world. You know how water pressure works. Everything runs down hill, Thats why there’s so much water down there.[;)]
It goes clockwise you dofus
Actually it goes counterclockwise in the Northern hemisphere and clockwise in the southern hemisphere. So what’s it do at the equator?
I’ve seen the little Tenshodo SPUDs (it stands for Self Propelled Universal Drive), but these are powered trucks with a motor driving both axles through a worm drive system - If anyone’s seen the old Tri-Ang mechanisms the design is very similar. SPUDs are handy when you want to motorize something without intruding into the bodywork - in the UK they’re often used to power diesel and electric multiple units as they allow you to fit an interior. However, SPUDs have no flywheel and I suspect they wouldn’t last long before burning out if you added the amount of ballast you would need to haul a decent length train!