teamgp

IB3800 packs I presume?

For grins, yesterday I tested the following stock motor setups with 4 month old & well used IB3800 packs and found some interesting results.

* Used both of my best Brood stock motors. A blueprinted Monster and P2K2.
* Re-serrated the existing 769 brushes with the Fussy Brush tool and shaved the leading and trailing edges of the brushes inward enough to eliminate the small diagonal cuts that exist on the four corners of a new brush. I shaved them about 1/4" down the side of the brush, so as to keep most of the brush body firmly seated in the hood. I didn't touch the comms at all, seeing as they only had two runs on them from the previous week.
* Unfortunately I didn't have my new Turbo Dyno available, but I ran them on the Fantom dyno that I've been using up to this point. The rpm and torque numbers dropped off a good bit, but the efficiency jumped up a lot more as well.
* On the track, I quickly found that I had to gear both motors up 3, count them THREE, teeth from rollouts of 23.8 & 25.9 to 26.6 & 28.7 respectively. They pulled very strong out of the corners well past six minutes per pack, top end was great and the temps never got higher than 175F & 188F respectively. I may have been able to gear them both up another tooth, but didn't want to risk smoking the hard work put in by good ol Pete.

I was able to equal my lap times of the previous weeks race throughout the first 2/3 of each run. However, I found that my times improved over the last 1/3 of each run by 1 to 2 tenths as the batts seemed to still have more of their runtime and voltage left later in the run.

I plan on doing the same test next week with full face brushes to see what the outcome is as well.

PitCrew

Good test. Whats going on is the brushes may be wrapping too far. I am curious to know if you know what the comm diameter is? What you should try doing is measuring the comm diameter and multiply that number by .51

Then cut your brushes to that width (the product of the comm dia x .51) and make sure you take equal amounts off each side of the brush as to not adversely affect the timing of the motor.

With a thinner brush you will get more torque, better effeciency, but less RPM, and you will see less power (watts) on the dyno. Big Jim used to trim laydown brushes to .140" i believe on the MVP motors. This is pretty close to right on. By using .51 x diam, you are getting just a very small amount of overlap, like a few thousandths. Should be really good.

teamgp

Thanks! Will do tonight while I rebuild the motors for tomorrows race. Do you think I may have shaved them down to skinny, since the torque went down as well as the rpm?

Brian Anthony

iTrader: (9)

EddieO,

Do you have any more 440 1.200 batteries left? I saw a pic of Dumas's car and no wonder he came off with 1 min of runtime left. Those things have to be killer. What percentage have that much runtime cause things gotta rip in stock with the voltage curve at like 400 they have to be amazing.

Brian

EddieO

iTrader: (6)

That wasn't a perfectly matched pack....the cells were 436, 438, 439, 440....voltage was kinda all over the place....

And, for stock or 19t.....on the track, the lower runtime stuff with the higher voltage always performs better.....not sure why, but it does.....Danny for SMC will tell you the same thing.....

Later EddieO

PitCrew

Well, I don't know. You need some calipers to measure as you are filing them down. Laydown brushes are right at about .190" wide.

So, if your comm was .290, then multiply that by .510. You get .148". That is the optimum width for full wrap with no "cogging" and no shorting. (The actual formula is to multiply the diameter by .5) I figured .510 should be a bit better for the fact that there is space between the comm segments which will allow you to run a slightly wider brush while still not shorting out.

I shaved some brushes down tonight to .160" with a comm that was about .298 (newer motor). The motor ROCKED, and when all other guys motors were comming off at around 180 degrees, mine came off barely over 140. After this change I also geared up one tooth, and knocked .3 off my previous best lap time. At end of night I went .6 faster than previous fastest lap on this layout.

I also slightly advanced the timing of the brushes by shaving .020 off of the trailing edge, and only .010 off the leading edge of the brushes. Some may argue whether that changes the timing, but it does. Imagine now your using a stand up brush where the contact patch is of your shaved laydown. The endbell would have to be advanced in order to place the center line of the contact patch of the brush in the same place as your "timed" laydown brush.

All I know is the motor was SCREAMING. Had punch, mad rip, and came off cool.

Don't forget that for most applications the laydown brush may still work just as good, or better. It depends on the motor, and track. But it fun to experiment.
brOOd baby!

Jan van Steeg

sorry, but this is not true.

its not 0.5, but sin60(degree) and that is 0,86602.

because there is a space between the comm segments the brush could be a little bit wider

Jan van Steeg

After thinking 5 minute's longer about it I has to say you are right pitcrew

it's nog sin60, but cos60

PitCrew

I was trying to keep it simple for those who dont have a scientific calculator.

Cos60 = .5

Hyper1

Thanks I have a little simple Calc that I keep in my pit trailer I didn't want to have to get out my $100 calc for use at the track.

teamgp

Thanks! I was starting to get a headache while reflecting back on the ole high school years...

Korey Harbke

iTrader: (13)

ahhhh thats easy stuff lol Cool post CJ.

-Korey

peter_robinson

iTrader: (21)

korey did you get your checkpoint teardowns on Dec. 1st???

PitCrew

Hey, I'm undercover here. Please don't reveal my secret identitiy...

teamgp

Some interesting results from yestedays race.

I freshened up the two Brood blueprinted motors (monster and p2k2) and shaved the leading and trailing edges of their new 767 brushes (with no hole this time) down to 1.7 width to match them to their comm widths according to the "scientificus formulaeus" above. The previous brushes were 769's (with holes) that were shaved down to a 1.9 width in the post above. The gearing changed slightly on both.

With the monster my avg lap times were off by one or two tenths, but the power was pretty consistent all the way through to the last lap where it only dropped .15 from my fastest lap time. However, it came off the track a little hot at 204F.

The p2k2 was another story. I had my fastest run (knocked off five seconds) and lap of the day which was only .06 off my record lap time. It came off the track at 177F.

Then I reverted back to my old self and idiotically decided to use one of my buddy's prime motors in the main, instead of sticking with the proven p2k2. Don't get me wrong, he (the Ikenator) does great "personal" motor work and after testing it for the right gearing, it was faster down the straight and had great pull out of the corners. However, it just didn't squirt me out of the corners as fast as the p2k2 and you could see the power fading the last couple of laps. I ended up loosing about a tenth on the average lap with it compared to the p2k2. Considering that very few passes are attempted at the end of the straight where your entering a tight chicane and pileups are frequent, I should have stayed with the Brood p2k2 power and increased the rollout by .5.

In reflection, I think the p2k2's spinup and efficiency are deceptively fast, whereas you think your going slower and are actually going faster. You can gear it to the moon as well.

I'll have a lot more tuning info later this week, as my dyno buddy (aka "The Mad Scientist" in electric drag racing circles), the Ikenator and I will be devoting half a day to tuning a stable of stock and 19t motors in preperation for the upcoming North/South Shootout race in NC. We'll be comparing dyno results from a CE 45, three fantoms (one older and two newer) and the little ol Orion. We'll definitely be playing with brush shaving/holes and such.

Thanks for the info "CJ", your cover is blown.