What does 13.5 and 17.5 mean in racing?

[DavidB1126]

What does 13.5 and 17.5 mean in racing? My LHS is having a race day on January 8th and they are doing sct and stadium truck classes. I want to see if I can qualify for it. I'm planning to race my slash. I still have the stock brushed system. I'm planning to get a brushless system, new body and lcg chassis and other stuff for it. If I do qualify I will probably be The slowest one there. I really don't care since I'm doing this for fun.

 

[pug]

Those numbers are motor turns, 13.5 in kv is 3500kv, 17.5 is 2500kv, I recommend 13.5 as it will be a little faster.

 

[WickedFog]

That is the turns of motors used.

 

[DavidB1126]

So would I be able to qualify with my Traxxas brushed system? I think the Titan 12 turn 550 is 3550 kv I'm not sure.

 

[WickedFog]

If it is a 12t, that is not in spec. It needs to be a 13.5 or 17.5.

 

[STONER RC]

What does 13.5 and 17.5 mean in racing? My LHS is having a race day on January 8th and they are doing sct and stadium truck classes. I want to see if I can qualify for it. I'm planning to race my slash. I still have the stock brushed system. I'm planning to get a brushless system, new body and lcg chassis and other stuff for it. If I do qualify I will probably be The slowest one there. I really don't care since I'm doing this for fun. View attachment 139476

whats up bud as far as the 13.5 and the 17.5. Are the number of turns of the copper wire in the motor. In racing you have your different classes. With SC or buggy, nitro. You also have motor size class. You can have a SCT 13.5 class or a SCT 17.5 class. So just sure that you are signing up for the correct class.

 

[Chubaka]

A good read on motors. There is a second one up top in the electric section also.

https://www.rctalk.com/forum/threads/turns-winds-kv-and-poles-explained.132791/#post-1314902

 

[Greywolf74]

A good read on motors. There is a second one up top in the electric section also.

https://www.rctalk.com/forum/threads/turns-winds-kv-and-poles-explained.132791/#post-1314902

I feel like that thread and the Comparing Lipos threads should be stickies.

 

[ahr43]

As a general rule of thumb 17.5 is considered stock class and 13.5 mod or modified class.

When you get to the track, seek out the RD (Race Director), show him your car or truck and ask what class he recommends you start in. RD's usually know which class to best direct you to. They base their recommendations on both your vehicle and skill level. If there is a novice or beginners' class, all the better. Often times, a novice class is not listed on a race flyer. That is a good place to start.

Goodluck. Cheers. 'AC'

 

[Chubaka]

I feel like that thread and the Comparing Lipos threads should be stickies.

Agree.

 

[Greywolf74]

Agree.

I asked but I guess my request was deemed not worthy or forgotten

 

[STONER RC]

I asked but I guess my request was deemed not worthy or forgotten

I feel ya... your threads definitely need to be stickies. They are both really good threads with really good info for newbies and vets alike. Especially the "Lipo comparison thread". That's just great info all around and can benefit everyone..just like with badges on this site..Every other site has a bunch of them and handed out frequently. But not here even if it's said they will be given they are not Givin..its like we are on the site of misfit toy's RC'ers... that's why you need to have the recognition of a Staff member. Your always around alot more then any other. And help alot of people. One you will get it bud (

 

[Greywolf74]

I feel ya... your threads definitely need to be stickies. They are both really good threads with really good info for newbies and vets alike. Especially the "Lipo comparison thread". That's just great info all around and can benefit everyone..just like with badges on this site..Every other site has a bunch of them and handed out frequently. But not here even if it's said they will be given they are not Givin..its like we are on the site of misfit toy's RC'ers... that's why you need to have the recognition of a Staff member. Your always around alot more then any other. And help alot of people. One you will get it bud (

Its all good. I'm just glad I can be useful

 

[pl9171]

What does 13.5 and 17.5 mean in racing? My LHS is having a race day on January 8th and they are doing sct and stadium truck classes. I want to see if I can qualify for it. I'm planning to race my slash.

Hi David,
Interesting.
They allowed me to race with a stock kit Slash (12T) in the open Stadium truck class at my local track; I was not the slowest; I qualified 7 out 13 and I was starting second on the B Main final;

You have to check from the race marshall the exact rules. Your race add is interesting; From our racing club;

17,5: It's the Spec 2WD Buggy class (every body has the same 17,5 motor)
13,5: we don't have
Stadium: open motor class; most of the guys have a 8,5T to 13,5T motors... (allowed Slash SCT 2WD)
2WD SCT: we don't have but they should allowed the open motor selection; some will have 8,5T to 13,5T (or basic Max 10 HW 3200 kv or 4000 kv)
2WD open: It's the mod buggy 2WD class; some will have 7,5T to 13,5T
4WD open; it's the mod buggy 4WD class; some will have from 4,5T to 13,5T... I have a 13,5T and I am able to do 15 out of 30 in Q (C Main Final). So, I ordered a 10,5T before Christmas...

The "problem" with the brushed 12T is the heat. After 4 minutes of full throtthle Q or races (Q or race is set at 5 minutes), it's over heating and motor "wag" a bit. HW or Reedy stuff have mega fan system, so they always keep below 100 Celcius...

Keep going.

 

[Terry.sc]

So would I be able to qualify with my Traxxas brushed system? I think the Titan 12 turn 550 is 3550 kv I'm not sure.

It is unlikely that if you just turn up you would be allowed, the rules are there to maintain a level playing field between cars.
You should contact them beforehand to ask if you could run in one of the stock classes as it's your first race, otherwise if you are allowed you are likely to be put in the open class in which you will be underpowered. You will find racing is a whole new level of RC driving. If they won't allow you to race with the stock motor at least you will not have a wasted trip.

17.5T and 13.5T are the physical number of winds of wire around the stators in the motor. While simple sensorless motors are measured by their kv as they will always run at that fixed speed, you cannot do that with a sensored motor as they are tuneable, and then the ESC programming can change even more settings so the kv rating isn't fixed. That's why race motors are measured by the number of turns.
I race in a 17.5T class and my selection of 17.5T motors have been tuned for different circumstances so they range from 2200kv to 3600kv, and running with boosted settings on the ESC the fastest 17.5T motors end up around 5000kv at top speed.