IMPBA FE Scale Rules Proposal #23-008

[Samuel Hagan JR]

The BOD unanimously accepted the proposal and it will be voted on by membership. From the August Roostertail issue-
View attachment 319098

Miss read. My vote will be yes.

 

[Dave Gilles]

Can I as a noob throw another thought out there? a way to control current could be longer races. cap mah and force 7 laps for example. gotta prop down.

sorry if this has been discussed ad nauseam

 

[Hydro Junkie]

Can I as a noob throw another thought out there? a way to control current could be longer races. cap mah and force 7 laps for example. gotta prop down.

sorry if this has been discussed ad nauseam

The problem with that is the presently used battery packs are limited on size based on a 3 to 5 lap race. By adding two more laps, battery packs could be damaged due to over-discharging(an expensive proposition) and, at the same time, ESCs could be damaged due to running power through them longer at more restricted levels(they will run hotter, just a side effect of more resistance). This is a case where you have to look at cause and effect. Running two battery packs that are capable of over 30 volts and 12 amp-hours of current combined at a more limited level is just asking to burn something up.
Since I don't run electrics, I would love to see what someone that does has to say. My reply is based on known electrical theory and Ohm's Law.

 

[kyleboyer]

3 words: Unlimited hydroplane racing.

 

[Dave Gilles]

The problem with that is the presently used battery packs are limited on size based on a 3 to 5 lap race. By adding two more laps, battery packs could be damaged due to over-discharging(an expensive proposition) and, at the same time, ESCs could be damaged due to running power through them longer at more restricted levels(they will run hotter, just a side effect of more resistance). This is a case where you have to look at cause and effect. Running two battery packs that are capable of over 30 volts and 12 amp-hours of current combined at a more limited level is just asking to burn something up.
Since I don't run electrics, I would love to see what someone that does has to say. My reply is based on known electrical theory and Ohm's Law.

well yes you can burn things up in a 3 lap race too if you over prop. in car or motorcycle racing you have to choose a tire compound that can go the distance of the race. You could say "if we do more laps it could be dangerous as tires could blow out"....yes they could. go harder tires. go smaller prop to make the race. a longer run time with a lighter load is no different....if anything its safer to pull less current for 20-40 more seconds.

 

[Hydro Junkie]

well yes you can burn things up in a 3 lap race too if you over prop. in car or motorcycle racing you have to choose a tire compound that can go the distance of the race. You could say "if we do more laps it could be dangerous as tires could blow out"....yes they could. go harder tires. go smaller prop to make the race. a longer run time with a lighter load is no different....if anything its safer to pull less current for 20-40 more seconds.

The issue isn't the current, it's the heat caused in the ESC by restricting the current. Over propping causes the motor to pull more power through the ESC, again causing more heat. Going with a smaller prop may reduce the load but it can also cause the motor to spin too fast, reducing its lifespan.
This is totally different than your racecar tire failure. When a racecar blows a tire, it's a mechanical failure in the rubber brought on by a combination of side stress loads and heat. The tires on my camp trailer, for example, can handle up to 84MPH. What will make them fail isn't the RPM they are spinning at, it's the heat being generated by the rolling resistance of rubber on concrete. Add the temperature of the concrete to that and tires can fail very quickly. I lost a tire between Cadiz and Paducah Kentucky on June 28th. The temperature that day was 93 degrees and we were traveling at between 70 and 75 MPH. The tire had plenty of rubber on it so that brings the question "Why did the tire fail?" The answer is simple, it got too hot and delaminated.

 

[Dave Gilles]

The issue isn't the current, it's the heat caused in the ESC by restricting the current. Over propping causes the motor to pull more power through the ESC, again causing more heat. Going with a smaller prop may reduce the load but it can also cause the motor to spin too fast, reducing its lifespan.
This is totally different than your racecar tire failure. When a racecar blows a tire, it's a mechanical failure in the rubber brought on by a combination of side stress loads and heat. The tires on my camp trailer, for example, can handle up to 84MPH. What will make them fail isn't the RPM they are spinning at, it's the heat being generated by the rolling resistance of rubber on concrete. Add the temperature of the concrete to that and tires can fail very quickly. I lost a tire between Cadiz and Paducah Kentucky on June 28th. The temperature that day was 93 degrees and we were traveling at between 70 and 75 MPH. The tire had plenty of rubber on it so that brings the question "Why did the tire fail?" The answer is simple, it got too hot and delaminated.

I was suggesting propping down a little bit to make the batteries last longer by reducing amp draw 5-10% keeping wiring cooler, esc, motor, all cooler as a way to implement a limit on classes.

the racing tire analogy is when you pick the compound; soft, med, hard, extra hard depending on a myriad of factors such as number of laps, track surface, ambient temps. Higher air pressures control heat in the tire by causing less carcass deflection. low air pressures cause more heat. but I simply meant its just highlighting a sanctioning rule and racers adapting to it.