SS1 Motor Parameters

[Bill Sellers]

I recently purchased an FDM SS1 motor and had the performance parameters measured. I thought that this information would be useful for those of us who like a little more quantitative information. Additionally, it will backup some of the performance results that have been observed by various FE boaters.

The results are as follows:
Kv = 1425 rpm/V, Rm = 90 mohms, Io = 4.0 amps

For comparison purposes, two other motors that are used a great deal have parameters as follows:

S700, 8.4V: Kv = 1467, Rm = 76, Io = 2.8
S700, 9.6V NEO: Kv = 1599, Rm = 57, Io = 3.0

FYI, the proper method to obtain Kv is to set the motor to neutral timing and then spin the shaft at a known rpm while measuring the voltage generated at the power leads. The SS1 timing is not adjustable, but it is at neutral.

Would anyone care to draw some conclusions from these numbers?

Bill

[Tony T]

I thought the SS1 had some advance. Interesting numbers.. thanks for the info.

[Doug Forrester]

Bill
How do those numbers for the 8.4BB and the 9.6 Neo compare to the ones published in ElectriCalc and MotoCalc. I see they are quite different to the ones in PCalc.

[Bill Sellers]

Doug,

The numbers for the 8.4BB and 9.6 Neo are from ElectriCalc.

Bill

[Jeff Wohlt]

Thank you, Bill!

So is the number of 90 mohms and the 4.0amps the key?

What does this tell us? SS1 is more efficient? Use more power to get the KV or what?

[Jeff Wohlt]

Here is a new motor as well for the 700 class. What are we looking for to make a good motor?

Can anyone explain what these number do and what we are looking for? Certainly not just KV. I have the 700 race that is blistering fast for rpm.


One thing I notice on this motor is the weight...all other 700 motors are in the 12.5 oz range.

Graupner Speed 700 S Turbo 9.6V
1938 KV
1.920 Curent
0.1360 Resistance
9.70 weight

[Bill Sellers]

Originally posted by Jeff Wohlt
What does this tell us? SS1 is more efficient? Use more power to get the KV or what?

Jeff,

Good question. Actually the SS1 is less efficient because of higher Rm (more power to heat). In additon, for a given voltage, the SS1 will produce less power b/c the lower Kv means the motor is drawing fewer amps and turning slower than a higher Kv motor. On the flip side, the lower Kv of an SS1 means it has more torque than the other two motors (which means it should perform better which larger props). Of the three motors, the 9.6V Neo is the "hottest" one b/c it has the highest Kv which draws the most amps which produces the most power (assuming the same prop and cell count for all motors).

I hesitate to give this analysis b/c someone will have empirical information and experience that says different. I couldn't argue with them since there are so many variables that go into a boat's performance. Lastly, the science of motor parameter measurement is such that different ways of measuring and different conditions of measuring can vary the results obtained.

Take care,
Bill

[AndyKunz]

Bill,

The easy way to get out of that one is "raw power" vs. "usable power."

I would put "usable power" into the discussion because if you don't have a prop to properly harness the power, ie, efficiently and completely get the power from the motor into the prop, you are wasting power.

It's like running a car in 1st gear. Sure, you can go real fast, and you have all kinds of torque available (because the RPM is high and also because of the low gear ratio) but how much torque do you need to go in first gear?!

I was trying to explain this to Jeff yesterday in a e-mails. My suggestion was to turn him loose on The Motor Handbook and go from there.

Andy

[Bill Sellers]

Andy,

That's right and the three motor parameters are static measures which only provide a common baseline for description of motor performance. For instance, if you look at the motors side by side, there will be some noticeable physical differences that can affect how much "useable power" can be attained when running under load. As an example, the internal fan blades and air vents are larger on the SS1 than the other motors - which would mean that it removes heat better when run under load.

I agree that reading the AstroFlight electirc motor handbook is a great way to learn the engineering behind brushed DC motors.

Bill

[Jeff Wohlt]

Thanks, guys. I need to get that book ordered. I did some searches and read some basics on the web.

Here is the NEO and the Turbo S model Graupner now makes. Between the weight difference...which to me 3 oz is significant and the kv that is the highest on any 700, next to the race version 700 which is 2055 kv--- that I just got but it is not effienient...just smoking fast for rpm.

My question for the below numbers is: Regarding current why does the S Turbo have lower current but produces more kv?

Looks like the S turbo could be a good motor? This one also has the enlarged air slots in the can.

Graupner Speed 700 S Turbo 9.6V #6371
1938 kv
1.920 current
0.1360 resistance
9.70 weight

Graupner Speed 700 BB TurboNeo9.6V #6305
1672 kv
2.170 current
0.0840 resistance
12.50 weight

Thanks for the info.

[RvE]

Bill
Interesting numbers. As others have mentioned, sometimes it is hard to figure out what this means to the typical FE boater due to variables.

If I understood your comments earlier correctly you were saying that the SS1 has the most torque and the NEO has the highest RPM, based on the numbers.

My empirical findings confirm this. The NEO is a hot motor with good RPM but requires a smaller prop. The fellow that won the CDN Nats in LSH (and always runs fast in our club racing) runs the NEO with a 45/55 mm prop (I think).

In 12 cell monos, our club runs some SS1, some 8.4 and 9.6 Speed 700s. Not sure I recall anyone using the NEO for the monos. The monos with the SS1 are generally the fastest - especially with big props! A few of us are running the SS1 with the Graupner K51 and this is a combo that is is hard to beat. So big props on the SS1 seems to be a reasonable approach.

By the way, the SS1 motor is only slightly warm after 6 laps of racing with a 51 mm props. The NEO requires more attention to motor heat!

Just some empirical info to support your findings.

Cheers RvE

[Bill Sellers]

Originally posted by Jeff Wohlt
My question for the below numbers is: Regarding current why does the S Turbo have lower current but produces more kv?

Graupner Speed 700 S Turbo 9.6V #6371
1938 kv
1.920 current
0.1360 resistance
9.70 weight

Graupner Speed 700 BB TurboNeo9.6V #6305
1672 kv
2.170 current
0.0840 resistance
12.50 weight


Jeff,

The current that is being listed for those motors is the parameter, Io, which is the amount of current it takes to just spin the rotor without any load. Therefore, factors which make it more difficult to break the rotor free to spin and to keep it spinning will cause the Io value to increase. Two of the biggest factors are bearing friction and brush friction. My guess from looking at the numbers you provided, it seems that the brush friction is high on the Neo 9.6V motor.

The Kv is not related to Io, but is a function of the thickness of the wire in the rotor coils and the number of turns per pole. For a given motor size, fewer turns will increase the RPM/V and more turns, the opposite. The resistance Rm will be related to Kv in the sense that a thicker gauge wire has less ohms per foot than thin wire.

I should probably go back and refresh my memory of this stuff. :D I hope this helps.

BTW, where did you get your info? I haven't seen a site that provided motor weights. The 9.7 oz. value for the S Turbo looks out of place for a Speed 700.

Take care,
Bill

[Jeff Wohlt]

Bill, thanks. I have amotor calc stuff. I am sending you the info by e-mail. So far they have been the same as others I have seen...they are rough but look at all the info for the hundreds of motors listed...even all the hackers are there.

[jmvde]

hi everybody, i've read your messages and, as i learn it at school, i agree fully with you ! ;) but i can't confirm it because i've only one engine and i don't know this famous SS1 (moreover, it's not imported in france )

however, i've something to ask you, even if this section is for brushed engine, i've been told that brushless are actually been tried and, their Kv is about 1500 rpm/volt, everybody say that they are more powerfull (higher rpm i would say) but, as you have written, the speed 700 do better ???!!!

So, are brushless better than what i eard ?

May i have this type of informations on a ultra 920 6 M ?

is that realist from 10 to 20 V ?

thank you very much !!:)

[Ken]

Well, the talk of 700 speed and all the motor claims had me a little confused so I decided to run a not so scientific test of a few of the 700's that I have. The specs never test with the same loads and voltages so I devised the test below to try to standardize some sort of comparision. It seems all the 700's were pretty close except for the SS1 which was higher RPM for the given load than any of the others. It even did beter than the 800's I threw in! I would like to see how much extra the SS1 draws in amps to come up with that extra power at a given voltage? Have to try to re-run tests with a watt meter.

Any comments on the data based on your experiences?


Loaded with 8" wood plane prop.
NiCad Batts. All topped after each run of 5-10 sec.
R.P.M. at volts
Motor----- 9.6V 14.4V 16.8V Aprx. Cost


775- 8.4V- 8,300 9,600 10,830 $35

Neo- 8.4V- 8,660 9,620 10,850 $65

Graup 9.6VBB- 8,300 9,600 10,800 $45

Dewlt12V can- 8,660 9,650 10,900 $21

Dewlt12V sp- 9,000 9,600 11,280 $42

Cordite-SS1- 9,120 10,350 11,430 $65

............................................... 22.8V 24V

820 BB 18V- 7,950 9,600 10,980 12,240 12,390 $65

800 BBX 18V- 7,890 9,480 10,860 12,360 12,420 $65



*Dewalt has two 12V motors. One is a Johnson type 700 can and the other is a Dewalt made motor slightly larger than a 700 with a Trinity .05 style motor can.



Last edited by Ken on 04-21-2003 at 09:51 PM

[Andrewg]

Ken

looks like those results are out of date

there is a new 700 8.4 v's is the same can etc as the SS1 which always was a marketing exercise on early versions of Maubuchi's update of its 775 series of motors

This process of redesigning the motor line has been under way at mabuchi for some years.


why pay $65 for a motor you can get for $44

[Ken]

Why pay $44 when you can pay $21?. The Dewalt 700 can motor from a Dewalt service center pulled harder (more RPM) than the others(accept SS1) for a given voltage. Would this not translate into greater speed given that all other variables are similiar?

Ken

[Bill Sellers]

Originally posted by Ken
[BWould this not translate into greater speed given that all other variables are similiar?[/B]
Ken,

It would have been better if you had also recorded the current being drawn when you performed your experiment. With that information you would have had an idea of how hard each motor was working, what duration you could get from each motor and which motors were more efficient. For example, if the Dewalt can drew 20 amps to produce that rpm under load, and the Neo only drew 10 amps under the same conditions, then your trade-off on which one to buy is not simply rpm versus cost. You want speed, but you also want to be able to finish the race too.

Bill

[BACKEMF]

Too Bad we didn't just stick with 1 simple motor that was the least expensive for performance, and reliability. I have run the Graupner 9.6 ferrite for 4 years and it still almost keeps up with an ss1. I paid 45.00 CDN, thats about $30.00 US I have even put 16 cells on it without any adverse reactions just faster. this was all done in a chopped Electro-vee with carbon props from 45 mm to 48mm. I gave up this year in the "Spec" Class just because everyone was starting to change the rules about a year ago or so. And everyone wanted to use the SS1 and then everyone broke the budget on a Fibreglass hull. This went from entry class to full on big budget "Spec" class. BOOOOOOOOOOOOOOOO!

[LOU]

Come on Ray, Don't knock it till you try it. All the rule changes were voted on. By going to a 4 min race your 9.6 is more competitive. It's the change to running an offshore course that puts the offset rudder boats at a disadvantage. No big deal just change your rudder location. Plus the rougher water favors the deeper Vees. You don't need a SS1 to win P-Spec offshore. I don't think its fair to ask New boaters to buy an inferior stock motor just so they can race. While it maybe cheaper it sure would bite to show up at the local pond with your spec race boat and get beat by some sport boater running an SS1 in a Villain:D
You pay 90 US for a good Speed controller whats wrong will 65 US for a motor that will last many seasons if cared for? And with the release of the New Graupner 8.4's the SS1 may just have to have a price drop to sell.

LOU

[AndyKunz]

Hey, just another month and it'll be $90 CDN for that same ESC.

If you are signed up at the Canadian Nats!

Andy

[BACKEMF]

I have just been getting in all the info lately on these new 8.4V BB's, from what I have read it appears to be slightly more efficient and a little better built, a little. You twisted my arm enough I think I may set up my Pspec Mono again. I can do 4 minutes on my old 1500's with a 48mm prop on my 9.6 BB almost as fast a the SS1 maybe 3-5 mph diff. which if you drive better than the rest works out not bad. time to paint and fix the canopy.
The only drawback to my motor prop setup is the torque effect of a large prop, makes for interesting driving. Hence all my flips.