View Poll Results: what's your tire choice?
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104
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4318LikesU.S. Vintage Trans-Am Racing Part 2
03-07-2016, 11:31 AM
#9241
I'm going to bring something up, not to start a crapstorm or to call anyone out, but simply to bring it to light.
At a recent event, I volunteered to do USVTA tech. At tech we measured the usual weight, battery voltage, ride height, etc. But I also had acquired a Fantom Facts Machine 2, which has the ability to measure stator resistances. With a simple 10 second check, it can determine whether or not the NOVAK motor has a 25.5 wind stator in it by measuring the resistance across two motor tabs.
Based on measuring 'known' new, good stators, it should be around 100 milliohms when measured across any two tabs AB, AC, or BC at 77F. Temperature will affect this measurement (about 0.2% per degree of temperature change).
What we found that there ARE Novak stators out there that have a black insert and look like the normal 25.5 stators but are NOT 25.5 winds. Some of the Crawler stators have lower winds, such as 18.5T and 21.5T. Which will create a huge performance advantage.
By measuring the stator resistance, I was able to detect a couple of non-compliant stators at the event. One was the 18.5T crawler stator. It measured at 50 milliohms when measured across two motor tabs. A 17.5 motor will measure at around 42 milliohms. So it was quite evident that it was non-compliant. Needless to say, that particular car was quite a bit faster (TQ in fact) and was DQ'd.
It's this motor stator:
http://www.amazon.com/Novak-Ballisti.../dp/B002SWTF18
The point of this post?
If you're putting on an event and you're serious about checking motors, you need to tech stator resistance. You can't simply look at the stator insert to tech it. But what you need is an ohm-meter capable of accurately measuring milliohms. Normal ohm-meters cannot measure at this level. The Fantom Facts Machine 2 is one such device, but is out of production. A cheaper option is the VICI VC480C:
http://www.amazon.com/Vici-Vc480c-Ac.../dp/B0090Y3W5W
Still not cheap at around $100, but any track should have this in tech, IMHO.
Just thought I'd throw that out there. I've been racing USVTA for two years now and it wasn't until I bought the Fantom Facts Machine 2 (for my own motor building/testing purposes) that it dawned on me what was going on.
With the proper meter, you can check stator resistance in less than 10 seconds in tech, it's non-invasive and can be done with the motor assembled and attached to the ESC. Just unplug the battery first. The readings are unaffected by the ESC motor leads.
Mark
At a recent event, I volunteered to do USVTA tech. At tech we measured the usual weight, battery voltage, ride height, etc. But I also had acquired a Fantom Facts Machine 2, which has the ability to measure stator resistances. With a simple 10 second check, it can determine whether or not the NOVAK motor has a 25.5 wind stator in it by measuring the resistance across two motor tabs.
Based on measuring 'known' new, good stators, it should be around 100 milliohms when measured across any two tabs AB, AC, or BC at 77F. Temperature will affect this measurement (about 0.2% per degree of temperature change).
What we found that there ARE Novak stators out there that have a black insert and look like the normal 25.5 stators but are NOT 25.5 winds. Some of the Crawler stators have lower winds, such as 18.5T and 21.5T. Which will create a huge performance advantage.
By measuring the stator resistance, I was able to detect a couple of non-compliant stators at the event. One was the 18.5T crawler stator. It measured at 50 milliohms when measured across two motor tabs. A 17.5 motor will measure at around 42 milliohms. So it was quite evident that it was non-compliant. Needless to say, that particular car was quite a bit faster (TQ in fact) and was DQ'd.
It's this motor stator:
http://www.amazon.com/Novak-Ballisti.../dp/B002SWTF18
The point of this post?
If you're putting on an event and you're serious about checking motors, you need to tech stator resistance. You can't simply look at the stator insert to tech it. But what you need is an ohm-meter capable of accurately measuring milliohms. Normal ohm-meters cannot measure at this level. The Fantom Facts Machine 2 is one such device, but is out of production. A cheaper option is the VICI VC480C:
http://www.amazon.com/Vici-Vc480c-Ac.../dp/B0090Y3W5W
Still not cheap at around $100, but any track should have this in tech, IMHO.
Just thought I'd throw that out there. I've been racing USVTA for two years now and it wasn't until I bought the Fantom Facts Machine 2 (for my own motor building/testing purposes) that it dawned on me what was going on.
With the proper meter, you can check stator resistance in less than 10 seconds in tech, it's non-invasive and can be done with the motor assembled and attached to the ESC. Just unplug the battery first. The readings are unaffected by the ESC motor leads.
Mark
03-07-2016, 12:49 PM
#9243
At the local level, checking for
1. Stator resistance is pretty simple and quick, if you have a milliohm meter or a Fantom Facts machine. You'll find out pretty quickly if the motor is in the ballpark of correct winds (e.g. 25.5 vs. 21.5 or 18.5 in NOVAK's case). Getting down to the nitty gritty of someone having a low -resistance stack is a little trickier if you don't have controlled conditions when measuring.
2. Blinky is pretty simple and quick. Yes, there are software hacks that can beat a visual check but at least you'll keep 98-99% of the folks honest.
3. Rotor checks are time-consuming, and then when do you do it? My preference would be a top-3 A-main teardown at the bigger local events/points races/trophy races. Let the competitors do it themselves and present the rotor to the Tech Director.
Just my $0.02 worth as a volunteer Tech Director at my local tracks,
Mark
The top 2 items are, IMHO, the biggest performance gains if left unchecked. A larger rotor is more a tuning item anyway.
03-07-2016, 01:32 PM
#9244
Nice!
At the local level, checking for
1. Stator resistance is pretty simple and quick, if you have a milliohm meter or a Fantom Facts machine. You'll find out pretty quickly if the motor is in the ballpark of correct winds (e.g. 25.5 vs. 21.5 or 18.5 in NOVAK's case). Getting down to the nitty gritty of someone having a low -resistance stack is a little trickier if you don't have controlled conditions when measuring.
2. Blinky is pretty simple and quick. Yes, there are software hacks that can beat a visual check but at least you'll keep 98-99% of the folks honest.
3. Rotor checks are time-consuming, and then when do you do it? My preference would be a top-3 A-main teardown at the bigger local events/points races/trophy races. Let the competitors do it themselves and present the rotor to the Tech Director.
Just my $0.02 worth as a volunteer Tech Director at my local tracks,
Mark
The top 2 items are, IMHO, the biggest performance gains if left unchecked. A larger rotor is more a tuning item anyway.
At the local level, checking for
1. Stator resistance is pretty simple and quick, if you have a milliohm meter or a Fantom Facts machine. You'll find out pretty quickly if the motor is in the ballpark of correct winds (e.g. 25.5 vs. 21.5 or 18.5 in NOVAK's case). Getting down to the nitty gritty of someone having a low -resistance stack is a little trickier if you don't have controlled conditions when measuring.
2. Blinky is pretty simple and quick. Yes, there are software hacks that can beat a visual check but at least you'll keep 98-99% of the folks honest.
3. Rotor checks are time-consuming, and then when do you do it? My preference would be a top-3 A-main teardown at the bigger local events/points races/trophy races. Let the competitors do it themselves and present the rotor to the Tech Director.
Just my $0.02 worth as a volunteer Tech Director at my local tracks,
Mark
The top 2 items are, IMHO, the biggest performance gains if left unchecked. A larger rotor is more a tuning item anyway.
03-07-2016, 08:01 PM
#9246
Tire options
Guys, it looks like HPI VTA tires are sold out at most hobby shops. Have anyone considered other tire options?
03-07-2016, 09:43 PM
#9247
Nice!
At the local level, checking for
1. Stator resistance is pretty simple and quick, if you have a milliohm meter or a Fantom Facts machine. You'll find out pretty quickly if the motor is in the ballpark of correct winds (e.g. 25.5 vs. 21.5 or 18.5 in NOVAK's case). Getting down to the nitty gritty of someone having a low -resistance stack is a little trickier if you don't have controlled conditions when measuring.
2. Blinky is pretty simple and quick. Yes, there are software hacks that can beat a visual check but at least you'll keep 98-99% of the folks honest.
3. Rotor checks are time-consuming, and then when do you do it? My preference would be a top-3 A-main teardown at the bigger local events/points races/trophy races. Let the competitors do it themselves and present the rotor to the Tech Director.
Just my $0.02 worth as a volunteer Tech Director at my local tracks,
Mark
The top 2 items are, IMHO, the biggest performance gains if left unchecked. A larger rotor is more a tuning item anyway.
At the local level, checking for
1. Stator resistance is pretty simple and quick, if you have a milliohm meter or a Fantom Facts machine. You'll find out pretty quickly if the motor is in the ballpark of correct winds (e.g. 25.5 vs. 21.5 or 18.5 in NOVAK's case). Getting down to the nitty gritty of someone having a low -resistance stack is a little trickier if you don't have controlled conditions when measuring.
2. Blinky is pretty simple and quick. Yes, there are software hacks that can beat a visual check but at least you'll keep 98-99% of the folks honest.
3. Rotor checks are time-consuming, and then when do you do it? My preference would be a top-3 A-main teardown at the bigger local events/points races/trophy races. Let the competitors do it themselves and present the rotor to the Tech Director.
Just my $0.02 worth as a volunteer Tech Director at my local tracks,
Mark
The top 2 items are, IMHO, the biggest performance gains if left unchecked. A larger rotor is more a tuning item anyway.
03-08-2016, 01:27 AM
#9248
03-08-2016, 05:16 AM
#9249
The only "alternatives" that would even be viable with the vintage rims are HPI's other vitlntage tires. They have one other treaded type and a slick type that fit the vintage rims.
I guess it would be up to the local track to allow the different types of tires, but they should make sure everyone is on the same type. But getting g away from the vintage style high sidewall tire would change the class too much. No matter what we should stay with the vintage rims.
As for the 25.5 rotors. What kind of advantages did you see the SmCo rotors have? From testing that a friend has done, they actually have less magnetic strength than the OEM rotor. Also the OEM rotor is now no longer available seperatly. You can only get one in a complete motor assembly.
I guess it would be up to the local track to allow the different types of tires, but they should make sure everyone is on the same type. But getting g away from the vintage style high sidewall tire would change the class too much. No matter what we should stay with the vintage rims.
As for the 25.5 rotors. What kind of advantages did you see the SmCo rotors have? From testing that a friend has done, they actually have less magnetic strength than the OEM rotor. Also the OEM rotor is now no longer available seperatly. You can only get one in a complete motor assembly.
03-08-2016, 06:24 AM
#9250
The advantage of a SmCo rotor is mostly imaginary. NOVAK wrote an article about SmCo vs. Neo here: http://images.amain.com/images/Link%...al_article.pdf
The SmCo holds its magnetic properties better under temp. The difference in rotor strength between the two is .09%/C. So if you assume the motor heats up 40C during a run, a SmCo rotor will have 40x.09 or 3.6% stronger magnetic field than a Neo rotor. So if you assume a rotor strength of 1200, the SmCo will have a 43.2 higher rotor strength. Due to motor efficiency, this would not translate to anywhere close to a 3.6% increase in power output.
I'd be willing to bet 99% of us couldn't tell the difference in a blind test. And as theProfessor noted, the SmCo rotors I tested had a lower rotor strength than the Neo rotors I tested. So it would be easy to make up the difference by starting out with a stronger Neo rotor.
At the local level, checking Stator resistance and blinky is much more cost/time effective than pulling EVERYONE's rotors during the day. Check the top 3 afterwards if you really want to deter rotor cheating.
Mark
The SmCo holds its magnetic properties better under temp. The difference in rotor strength between the two is .09%/C. So if you assume the motor heats up 40C during a run, a SmCo rotor will have 40x.09 or 3.6% stronger magnetic field than a Neo rotor. So if you assume a rotor strength of 1200, the SmCo will have a 43.2 higher rotor strength. Due to motor efficiency, this would not translate to anywhere close to a 3.6% increase in power output.
I'd be willing to bet 99% of us couldn't tell the difference in a blind test. And as theProfessor noted, the SmCo rotors I tested had a lower rotor strength than the Neo rotors I tested. So it would be easy to make up the difference by starting out with a stronger Neo rotor.
At the local level, checking Stator resistance and blinky is much more cost/time effective than pulling EVERYONE's rotors during the day. Check the top 3 afterwards if you really want to deter rotor cheating.
Mark
03-08-2016, 08:37 AM
#9251
Isn't checking motors after the race a somewhat established practice? It seems to be a reasonable thing to me.
03-08-2016, 08:40 AM
#9252
67 VTA Camero in swimming pool.....
Found a new place to run my VTA Camaro right in my back yard garden. Just empty the pool and there you are......nothing to hit and a perfect oval track with pretty good grip........LOLhttps://youtu.be/G7i1c73ohY0
03-08-2016, 08:45 AM
#9253
I was at that usvta indoor nats race also. I didn't race vta but i can say that there were differences in the rotors. Apparently, some simco (sp?) rotors found their way into the 25.5's. These rotors provided an advantage and needed to be removed. Brian Mcgreevy - you want to weigh in on that?
If there really isn't a true or significant performance difference, I guess it should be looked at to determine if it could be allowed going forwards. For now though, a decent number of folks are upset because the wrong (not legal) rotor was installed in their motor from the factory, without their knowledge.
My motor/rotor is a 5 yr old converted SS to Ballistic with the original rotor.
