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Old 10-15-2008, 02:08 PM   #1
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Default which motor to choose in 27T- 17.5 category?

I will be competing in a local competition in a FUN-class as I am rather inexperienced.

In this class the following motors are allowed:
brushed 27T:
* Peak RS24 (PEK8305)
* Orion Core 27t (ORI20020)

brushless 17.5:
* Orion 28142
* LRP 50850
* NOSRAM 91850
* Losi B9406

I can find details (rpm², rpm/Kv, watt,...) about the LRP-motors but not from the rest.

could someone provide me with more info on the Orion 17.5 and/or the Losi 17.5.
about the Peak-motor?

And, what motor should be best for this stock-racing? (carpet, indoor)
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Last edited by Low_E; 10-16-2008 at 03:49 AM.
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Old 10-15-2008, 03:32 PM   #2
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The LRP brushless is a pretty good motor. I would definatly recomend it.
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Old 10-15-2008, 03:59 PM   #3
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The Losi motor is made by Hacker. Hacker's 17.5 is very fast, so the Losi should be good. I believe it is the same motor.
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Old 10-16-2008, 02:03 AM   #4
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I got a blueprinted Peak RS24 today, this is what the dyno sheet says

Battery Simulation: 7.4v

RPM: 28,200 Rpm
Power max: 119.1 W
Power Avg 76.1 W
Efficiency Max: 66.3%
Efficiency Avg: 43.5%

I very nice upgrade from a 540J Silver Can
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Old 10-16-2008, 03:51 AM   #5
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the LRP-site gives a 16560 rpm-number for their 17.5 X11 Brushless motor..

That's a lot less rpm then this Peak motor.
I do'nt understand how these motors an be comparable then, and used in a same class.

On the other hand, teh LRP seems to have much more power (153 Watt compared to the 119 watt from the Peak-motor)
Does that mean the Brushless motor has a lot more torque?
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Old 10-16-2008, 07:18 AM   #6
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I would say the LRP has alot more torque then the peak. I don't really understand how brushless works, as I'm not going to be using BL for a while I'm not going to learn about them for a while.
By using http://www.rcracing.com/Gear_Ratio_Program_1100.cfm I did a top speed calculation for my TT01's current setup with the different RPM from the two motors. 22P/61S @ 7.21:1 with 2.6 transmission ratio and 63mm tyres
LRP: 16560 = 27.28 kph
Peak: 28200 = 46.46 kph
Silver: 15000 (approx) = 24.71 kph
This is only a theoretical top speed calculation. I would say since the LRP has more power it would probably better suited to tight technical tracks more so then the Peak.
But you should also take into consideration that a 540 Silver Can is approx 15000 rpm
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Old 10-16-2008, 07:30 AM   #7
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If you are racing in a FUN class, don't get too beat up on deciding how much power a motor gives out.

Manufacturing tolerances, difference in power between brushed/BL and how the car is set up/geared and who is the better racer will determine who does well and who doesn't.

You might have someone flying past you on the straight but can't find lap consistancy.

Even the track layout will factor in to who can do well and who can't. All i'm saying is the motor is a small part of the bigger picture
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Old 10-16-2008, 08:27 AM   #8
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from my pov a well maintained and tuned 27 turn stocker will out perform a 17.5. Yet with the 27 turn you're going to spending most of your time cutting comms, cleaning the motor, cleaning brushes. 17.5's will typically turn the relativly the same speeds/times while still being very easy to drive, very low maintanance and give you more time to setup your car and just drive.

If you were a seasoned vet... i'd say go brushed stock. for just starting out, or for racing for the sake of having fun... 17.5 all the way.
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Old 10-16-2008, 09:48 AM   #9
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The motor rpm does not dictate your cars top speed. The peak rpm measurement is taken with no-load. As soon as you put a drive-train and areodynamic load on the motor, it will bog down considerably. This is where your peak power numbers come into play (just like real cars). The lower the power, the earlier it will bog.

Gearing decides what motor-rpm is acheived at what speed, and top speed will be determined by the point where power requirements exceed power production. This is why shorter FD ratio results in lower top speeds.

In the end, the motor with more torque AND power is better. The rpm is not as important...

Of course I could just be talking out of my butt...
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Old 10-16-2008, 10:38 AM   #10
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Quote:
Originally Posted by Scooter79rs View Post
I would say the LRP has alot more torque then the peak. I don't really understand how brushless works, as I'm not going to be using BL for a while I'm not going to learn about them for a while.
By using http://www.rcracing.com/Gear_Ratio_Program_1100.cfm I did a top speed calculation for my TT01's current setup with the different RPM from the two motors. 22P/61S @ 7.21:1 with 2.6 transmission ratio and 63mm tyres
LRP: 16560 = 27.28 kph
Peak: 28200 = 46.46 kph
Silver: 15000 (approx) = 24.71 kph
This is only a theoretical top speed calculation. I would say since the LRP has more power it would probably better suited to tight technical tracks more so then the Peak.
But you should also take into consideration that a 540 Silver Can is approx 15000 rpm
you cant compare top speeds in brushed and brushless based on the same gearing, Brushless 17.5 can NOT be geared like a 27T and get the same result.
To have a brushless 17.5 compete at 27T level in lets say the for example a T4 I was running lets say 19P/87S with a 2.0 tranny ratio but would run a 26P/75S with a 17.5 those are completely different ratios because brushless have different powerbands
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Old 10-16-2008, 03:29 PM   #11
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Quote:
Low_E the LRP-site gives a 16560 rpm-number for their 17.5 X11 Brushless motor..

That's a lot less rpm then this Peak motor.
I do'nt understand how these motors an be comparable then, and used in a same class.

On the other hand, teh LRP seems to have much more power (153 Watt compared to the 119 watt from the Peak-motor)
Does that mean the Brushless motor has a lot more torque?
Brushed motors will generally have more rpm while BL motors have more torque.
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