Author Topic: project broken parts (Read 12963 times)

CHRIS_MORRISON · « **on:** March 30, 2005, 08:58:05 PM »

you take one 12l3
add a 96 spur and a 26 pinion
one six cell 3300
and a ten turn single
take the car to the track this saterday

wait 30 seconds and watch the carnage

CHRIS_MORRISON · « **Reply #1 on:** March 30, 2005, 09:01:21 PM »

im bringing a video camera i need a someone to run it? :twisted:

jarrodH · « **Reply #2 on:** March 30, 2005, 09:20:23 PM »

ill run the camera for ya, if you want

« **Reply #3 on:** March 30, 2005, 10:09:10 PM »

if i dont see atleast one wheel go flyin id be disappointed

« **Reply #4 on:** March 30, 2005, 10:09:44 PM »

if i dont see atleast one wheel go flyin id be disappointed

haddow · « **Reply #5 on:** March 31, 2005, 01:50:02 AM »

only 6 cells?...yawn.

Grinder · « **Reply #6 on:** March 31, 2005, 04:22:25 AM »

I've been running my TC4 with my Novak SS 5800 7-cell geared 35/69. Man does it ever eat tires....

10 turn single isn't a very high reving motor is it? Lots of torque...

CHRIS_MORRISON · « **Reply #7 on:** March 31, 2005, 06:51:46 PM »

30,000 rp+ direct drive your car wold seem to be standing still compared to this car

Tom · « **Reply #8 on:** March 31, 2005, 07:34:28 PM »

Why don't you gear it up? Most people run taller gears than that in stock! If you want to go fast, gear to the moon; your motor can handle it in a 1/12 scale car!

CHRIS_MORRISON · « **Reply #9 on:** March 31, 2005, 07:36:33 PM »

30 pinion 88 spur 64 pitch
or
31 pinion 66 spur 48 pitch

what do you think tom

Tom · « **Reply #10 on:** March 31, 2005, 08:47:50 PM »

Quote from: "CHRIS_MORRISON"

30 pinion 88 spur 64 pitch
or
31 pinion 66 spur 48 pitch

what do you think tom

Well duh! 31/66 is WAY taller than 30/88! Go with the 31/66! That'll get it moving.

I'd definately watch then.

roagracer · « **Reply #11 on:** March 31, 2005, 08:56:54 PM »

I will be there. Also to practice a bit.

CHRIS_MORRISON · « **Reply #12 on:** March 31, 2005, 09:26:32 PM »

tom i know that already i was just being a gufe

Blake · « **Reply #13 on:** April 01, 2005, 03:16:24 AM »

Hey Chris,

After we shoot footage of this, maybe the Navy will let you jump over one of their boats....

Blake

cyrrus · « **Reply #14 on:** April 01, 2005, 01:10:33 PM »

Hey jody and Blake PM sent

Sorry chris didn't mean to hijack you thread.
By the way when do you plan on doing this any how.

Tom · « **Reply #15 on:** April 01, 2005, 01:40:53 PM »

Hey, Blake. I sent you an email a while ago.

I thought everybody reading the IROCC forums would be interested in knowing that, since it's so difficult for you to figure that out yourself.

Oh, and Jody, I think I might have sent you an email a while ago too.

Let's see, who else have I sent messages to. I know you are all just DYING to know. . .

Blake · « **Reply #16 on:** April 01, 2005, 01:59:14 PM »

Cool it Tom. Not everyone has grown up surrounded by email, newsgroups, forums, and the etiquette that goes along with these communication mediums.

And the truth of the matter is, there is no obvious prompt that you have received a private message. I know that I've spent some time browsing around the forums and never noticed that I had a private message waiting for me.

Anyway, Andrew, as I'm sure you're aware, Tom is just kidding around with you. And, as you've witnessed at the track, he's actually quite a nice guy!

Blake

Mikemuncher · « **Reply #17 on:** April 01, 2005, 07:20:47 PM »

Hey Tom....did ya get my email..... :lol: :lol: :twisted:

Grinder · « **Reply #18 on:** April 02, 2005, 02:40:13 AM »

Quote from: "CHRIS_MORRISON"

30,000 rp+ direct drive your car wold seem to be standing still compared to this car

Well Chris I'm just an uneducated newbie but...

You are running 26/96 on a single wound 10T running 6 cells. You also say its a 30K RPM motor. I don't know what vehicle you are running it in but I'm sure your final drive ratio is around 8:1 ish. Just on your spur/pinion you are 3.69:1

My car is a TC4 and I'm running 35/69 which gives me spur/pinon of 1.97:1 and a final drive ratio in the low 5:1

My motor runs at 5,800 RPM per volt so with seven cells (8.4V) thats 48,720 RPM

So here's the summary for ya;

Your drive ratio : about 8:1
My drive ratio : about 5:1

Your motor RPM : 30,000 RPM
My motor RPM : 48,000 RPM

So unless you are standing on the hood of my car I don't think it will look like my car is standing still....

Of course as I said I'm just a newbie - I haven't even raced anyone yet so feel free to correct/flame on....

Blake · « **Reply #19 on:** April 02, 2005, 03:36:23 AM »

Hey Grinder,

The car Chris is referring to is a 12th Scale car. These cars do not have any further gear reduction after the pinion/spur. There is no other transmission at all in these cars. So, his final ratio will be 96/26=3.7 overall. If he goes with Tom's advice (and I hope that he does) then he'll have a 66/31=2.1 overall gear ratio.

A 12th Scale car has smaller tires than your touring car but he'll still likely net out at a taller ratio than you.

As for motor RPM, those numbers really mean nothing. The manufacturer just prints those on the labels because it sells more motors. Those RPM figures are based on "free wheeling" the motor with absolutely no load on it. When you strap it in a car it's a completely different ballgame.

Anyway, Chris' setup will be fricking ballistic! I took a similar setup to the Velodrome (and the ferry lineup) one year and it was crazy. Of course it ended in complete destruction....

Should be fun to watch!
Blake

CHRIS_MORRISON · « **Reply #20 on:** April 02, 2005, 10:51:31 AM »

iv got a motor dyno and my rpb 13 realy 32,512 rpm at 5 volts

CHRIS_MORRISON · « **Reply #21 on:** April 02, 2005, 10:52:54 AM »

iv got a motor dyno and my rpm #s are 32,512 rpm at 5 volts

Tom · « **Reply #22 on:** April 02, 2005, 11:42:25 AM »

Quote from: "Blake"

As for motor RPM, those numbers really mean nothing. The manufacturer just prints those on the labels because it sells more motors. Those RPM figures are based on "free wheeling" the motor with absolutely no load on it. When you strap it in a car it's a completely different ballgame.

To prove this point, let's calculate the motor manufacturer's projected top speeds, which won't reflect reality in any way.

A 5800 rpm / volt motor in a touring car with 7 cells and a final drive ratio of 5:1 (I don't know your transmission internal reduction, so I'm trusting that number) will have a projected tire speed of 9744 RPM. With a standard touring car tire diameter of 62mm, that works out to just under 195mm / tire revolution. You end up with 9744 * 194.78 = 1897924 mm / min, which works out to 31.63 m/s, or 114 km/h, or 71 mph. That is quite a bit less than the 41.9 mph you clocked your car at; as a matter of fact, 41.9 mph works out to a motor speed of. . .

(gets out calculator again)

1123859 mm/min, which is 5770 wheel RPM, which is 28,850 motor RPM. Quite a bit off from your stated 48,720 RPM, ain't it?

As for Chris, who knows what motor speed to start out with? He claims 30,000 RPM (at what voltage and load settings? Who knows?), and he also has measured it at 32,512 RPM at 5 volts. He'll be running it at a higher voltage than that, but let's give your car the benefit of the doubt (even though the rolling resistance of a 4wd car is far greater than that of a 1/12 scale car) and project Chris's speed as though his motor ran at 30,000 RPM as he initially claimed.

Chris will have a calculated wheel rotation speed of 30,000 / 66 / 31 = 14,091 wheel RPM (sounding better already, ain't it?). Although I don't know his tire diameter (foams will range significantly in diameter during their lifetime unlike rubber tires), I'll take a reasonable number of 45mm. That's the tire diameter of the tires on my car, which is fairly worn out, which is consistant with the above assumptions against Chris. That works out to a projected speed of 1,992,055 mm / min, or 33.2 m/s, or 120 km/h, or 74 mph.

So, it's a tad closer than I thought it would be, but here's the way it works out.

We're assuming your motor runs at it's rated speed, when we have shown by data supplied by you that it actually runs at about 60% the rated speed.

Chris has claimed a motor speed of 30,000 RPM on 6 cells (7.2 volts), when he has actually measured the motor at 32,512 RPM on 4 cells (5 volts). We could easily justify a motor speed of 48,768 MPH given the facts Chris has presented to us. That would boost his top speed to 194 km/h, or 120 mph.

The fact is, it is just about impossible to project a cars top speed given the data published by a motor manufacturer. It would be possible to come up with realistic projections given dyno readings and having some idea of the efficiency of the car (aerodynamic effects, drive train drag, etc.), but not having that ends up with discussions like the above, where people just say that their car boasts higher specs, which is about the same as saying that you've spent more money on your car, therefore it's better than the other guy's.

I would expect Chris's car to go way faster than Grinder's, for the following reasons:

Chris is running it in a 1/12 scale car, which boasts:
- Far more aerodynamic than Grinder's (narrower, lower, better shape)
- Far less drag (2 gears, 6 ball bearings in drivetrain)
- Far less mass (we can't wait for the car to reach top speed, so we have to take acceleration into account for excitement)

It'll definately be exciting, but it sure won't prove much! I would be quite interested in racing the two cars together to see which one handles the speed better. I suggest at least a show-down at the velodrome, but a road course would rock as well!

The problems are:
These figures negate air drag in the motor (quite significant), and on the chassis (also quite significant at these car speeds). They also negate bearing drag (motor and drivetrain), and brush drag (on Chris's car, not on Grinder's, which is again significant, since this is one of the major advantages of a brushless motor). They also don't take into account rolling resistance, which is a lesser effect than all the others previously mentioned. Contrary to popular belief, rotating weight, the mass of the car, etc., have no effect on the top speed of the car except for the influence on more rolling resistance (in bearings and tires), since the mass (rotating or otherwise) only affects acceleration, not top speed, and we are compairing two cars based on claimed top speed.

Tom · « **Reply #23 on:** April 02, 2005, 11:56:02 AM »

Aah, I knew I forgot to mention something!

Based on Chris's projected top speed with measured motor speeds, his car would go 120 mph, or 194 km/h. Given the 60% degradation of projected performance in the real world (which should be less for Chris than Grinder), that would result in a more realistic projected top speed of 72 mph or 116 km/h for Chris.

So, worst-case scenario, Chris's cars specs. should result in a car at least as fast as Grinders, and a more realistic scenario puts Chris's actual car speed just over Grinder's theoretical speed.

CHRIS_MORRISON · « **Reply #24 on:** April 02, 2005, 12:03:13 PM »

the internal ratio of Grinders car is 2.5 to 1

haddow · « **Reply #25 on:** April 02, 2005, 02:23:02 PM »

I just want to see a firey crash. Or at least a smoked ESC and a melted motor.

Grinder · « **Reply #26 on:** April 02, 2005, 08:00:57 PM »

I stand corrected on the guestimated final drive ratio of Chris's car - that will definately make a major difference in the top speed. I'm not debating that his car would be faster than mine either - I was just pointing out it wouldn't "look like it was standing still".

Also the brushless in the same vehicle should outperform a 10 Turn single. Besides I don't have to cut the comm if I find what's left of the car

Besides the TC4 runs outta track real fast doing 42 MPH (personally I think the GPS errs on the slow side for some reason - my Stampede doing 37 MPH seems WAY slower than the TC4 doing 42 MPH yet the results are repeatable).

I could always throw the HV-Maxx with 16 cells x 4400 RPM/volt.... I'd have to use GP 1100 2/3A cells though... but like I said the SS 5800 is uncontrolably fast anyhow so it really would be pointless..... pointless but fun

Roagracer and I went out today. His Speed Gems II 13T tripple runing at 26/73 on 7-cells was pretty darn close to my SS 5800 21/69 on 6-cells. Unfortunately my rubber tires turned into foamies as the day progressed. Anyone have a recomendation for a high wear tire?

Tom · « **Reply #27 on:** April 03, 2005, 05:51:36 AM »

A stock motor and a race track.

Stock is as boring as heck in a big open parking lot, but it's great fun when you have a race track set up. I think you'll find most people will agree with that. It's not unheard of to go a whole season on one set of tires, and just about everybody could go through a season with two sets.

It sure is a heck of a lot cheaper than what it sounds like you are doing!

Grinder · « **Reply #28 on:** April 07, 2005, 02:32:05 PM »

Aww I was just messin around till I can try racing out. Man I should have waited till April to get my car - I can't wait!!!

I just have zilch for driving experience. Do they have an E-Main for newbies

Blake · « **Reply #29 on:** April 07, 2005, 04:34:56 PM »

Hey Grinder,

Don't worry about being new to racing. You'll be slotted into the lower heats where you'll be racing against other newer racers. Then, as you improve, you slowly move up through the heats. Last year, Robert was in exactly the same boat as you are this year.

Blake

Grinder · « **Reply #30 on:** April 08, 2005, 09:06:11 PM »

Boat? I though we were racing cars.... I'm so confused....

Poll

would you watch

Author Topic: project broken parts (Read 12963 times)