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Old 12-29-2009, 05:52 AM   #1246
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Once you get beyond the extremes (less than one amp, more than three at five volts), we fiind very little direct correlation between amp draw when a motor is freewheeling (unladen) and actual power.

As Jeff says, there are a LOT of variables that can cause higher amp draw, including that the motor has picked up a screw or staple from the track or is otherwise binding or inefficient. Lower often means that the motor brushes simply have not yet been fully broken in.
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Old 12-29-2009, 12:30 PM   #1247
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Thankyou very much I was sort of comfused cause I got a higher number with my pk2 than my stock 15 turn firebolt I figured the pk2 had more power but when i put in bearings the pk2 amps dropped. I had bushings in it before. I am racing spec class short course with brushed motors when everyone is running brushless. I have tried all kinds of gears, I dont have a lathe but trying to get the most out of that pk2 so I can at least keep up better. I am running a really strong esc but can not keep up with them brushless trucks.
just annoying when I am consistant with no crashes and they can crash and pass me up again when I am driving that truck with everything it's got.
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Old 01-01-2010, 02:33 AM   #1248
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How are you guys measuring the RPMS on these things? I'm looking around for specialized motor dynos but they don't seem to be common.

Out of curiosity I just hooked a 7.2v pack up to a brand new johnson motor that had been water dipped for 10 mins and got 1.34 amps, but I have no way of knowing the rpm. I also tested the voltage of the pack and got 8.0 volts.

Then I tested a mabuchi motor that came out of my tt01, has a bit of runtime but no water dipping, and got 1.50 amps out of it, and I'm told it hauls, but I've never actually run it myself. :P
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Old 01-01-2010, 09:22 AM   #1249
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Orion, Peak, Trinity and Much More all sell (or have sold) a device called a Motor Master that uses an optical pickup (they call it a bushing) to measure motor RPM and amp draw at specific voltage levels. APS also sell a device that combines a motor rpm device and a charger in the same unit. With the advent of brushless technology, these units are becoming harder to find.

Expect to pay between $75-160 for a used or new unit, plus you will need a power supply to run it. You might also want to consider putting a 'Wanted' ad in the for sale section of this forum.
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Old 01-01-2010, 09:38 AM   #1250
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what is a good way of "running in" a new silver can ??

i want a bit of an edge over my race mates with the M chassis

any advice would be nice so i can have a screamer
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Old 01-01-2010, 11:21 AM   #1251
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You have 83 previous pages in this thread to answer that question.
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Old 01-01-2010, 12:37 PM   #1252
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Originally Posted by ZiG-87 View Post
How are you guys measuring the RPMS on these things? I'm looking around for specialized motor dynos but they don't seem to be common.

Out of curiosity I just hooked a 7.2v pack up to a brand new johnson motor that had been water dipped for 10 mins and got 1.34 amps, but I have no way of knowing the rpm. I also tested the voltage of the pack and got 8.0 volts.
Please keep in mind that RPM is only half the power equation. Horsepower is RPM * Torque /5252. If you have lots of RPM and no torque, you have an average motor.

As brushed motors are used, the strngth of the magnets begins to erode due to heat, especially with cheaper magnets. This allows your RPM to increase, as there is less reistance to the field generated by the armature, but the torque drops off. And the torque drops at such a rate that the gain in RPM doesn't make up for it. The best 27T brushed motors I ever had were high in torque, and low in RPM. You would need a real dyno, sucjh as a TD45 to check, not some RPM guage.

And no load Amp Draw means virtually nothing. Think of it like a racing engine- if you have more Power than the other guy, who cares if you only get 90% of the mileage? Especially when there are no pit stops and you have plenty of fuel on board.
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Old 01-01-2010, 12:48 PM   #1253
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Please keep in mind that RPM is only half the power equation. Horsepower is RPM * Torque /5252. If you have lots of RPM and no torque, you have an average motor.

As brushed motors are used, the strngth of the magnets begins to erode due to heat, especially with cheaper magnets. This allows your RPM to increase, as there is less reistance to the field generated by the armature, but the torque drops off. And the torque drops at such a rate that the gain in RPM doesn't make up for it. The best 27T brushed motors I ever had were high in torque, and low in RPM. You would need a real dyno, sucjh as a TD45 to check, not some RPM guage.

And no load Amp Draw means virtually nothing. Think of it like a racing engine- if you have more Power than the other guy, who cares if you only get 90% of the mileage? Especially when there are no pit stops and you have plenty of fuel on board.
You also have to remember what these guys are using the motors for. The vast majority of the silver cans in the usa go in mini cars, which have an upper limit for the gearing. So RPM is the only way to increase the speed beyond what they have. in fact a torque motor can be detrimental, since they can't get at the power with gear. F1 or GT3 Tamiya class cars are in a different boat.
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Old 01-01-2010, 01:40 PM   #1254
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Originally Posted by sidecarphil1 View Post
...i want a bit of an edge over my race mates with the M chassis

any advice would be nice so i can have a screamer
buy red dot motors from rccardr. period.

on a track with a long straight, back off a little to make it look close.
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Old 01-01-2010, 01:44 PM   #1255
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Quote:
Originally Posted by ZiG-87 View Post
How are you guys measuring the RPMS on these things? I'm looking around for specialized motor dynos but they don't seem to be common.

Out of curiosity I just hooked a 7.2v pack up to a brand new johnson motor that had been water dipped for 10 mins and got 1.34 amps, but I have no way of knowing the rpm. I also tested the voltage of the pack and got 8.0 volts.

Then I tested a mabuchi motor that came out of my tt01, has a bit of runtime but no water dipping, and got 1.50 amps out of it, and I'm told it hauls, but I've never actually run it myself. :P
ZIG - I can bring along my dyno to the track one night if you really want to know, but after running more than a few of 'em, I can tell you right now what to expect...
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Old 01-01-2010, 06:55 PM   #1256
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Scott, that would be awesome. I've done more searching now and I see that a dyno isn't this big microwave-sized thing I thought it would be, so yeah, I would appreciate it if I could see how my tt01's black can is, and which of these two silver can motors is better.. I'll be at KARZ tomorrow, but not Sunday.. and then next week. So whenever is convenient for you.
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Old 01-07-2010, 10:37 PM   #1257
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Hey RCCARDR guy are you the one who distributes them there Red Dat moters. I was wonderin of i kud buy one them there bad boys. Heard that they was the best ones out there to get if I wanna win me a big race culd you please Personally Mesagge me for detailis. Thank ya
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Old 01-07-2010, 10:56 PM   #1258
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Amp draw at no load can be an indicator of the torque in the motor by virtue of your own explanation, i.e. the more magnet force has to be overcome, the more current drawn. Sure, this is not the only reason a motor would pull high amps, and there's quite a few detrimental reasons why it would, such as misaligned bushes, too much tension on the brush springs, etc., so i am not going to say it is the best way to assess a motor but if all else is sorted, and you have an accurate device to measure rpm and amp draw, is a good enough test at least to check what motor can go in the bin.
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Old 01-08-2010, 07:50 PM   #1259
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Yes, niznai, I agree. There is potential there, all things being equal. If onyl things were equal more often...

Swifty- back in your box!
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Old 01-14-2010, 07:19 AM   #1260
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Yes, niznai, I agree. There is potential there, all things being equal. If onyl things were equal more often...

Swifty- back in your box!
please will you tell me how much one of your silvercans will cost me

i sent you a message but heard nothing back

also including shipping to holland

cheeRS Phil
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