Brian McGreevy

iTrader: (10)

I agree Kevin, the larger 20 tooth pulley feels so much faster everywhere than the 17 tooth with the same Final Drive. Prove me wrong on this guys?? If physics says it shouldn't be so, then why is it?

RichChang

"Feel" and "Is Faster" are two entirely different things.

Were your overall lap times faster and by how much?

And, as was mentioned many times now, weight location comes into play.

Think about the mod people have been doing to the TC3 in regards to battery location. They are moving the batteries in to the centerline and feeling a difference. Those batteries are not moved in much. Weigh a motor and see how much it weighs in the grand scheme of things. It is pretty heavy.

And, if so, it is pretty hard to simulate exactly the same conditions - especially with electric cars since battery condition, motors, etc come into play.

For example, most battery packs are better on their 2nd charge. And, to find two packs to run side by side with exactly the same numbers and discharge rate is not easy.

Also, driving comes into play. Yeah, your lap times may be faster in testing with the different spur, but maybe you just drove a better line.

Anyways, I'm done discussing this. This is getting to be pointless since I have better things to do with my time.

Believe what you want and go with what you want. These are toy cars and it makes no sense to me to continue to try and convince people of something that physics explains.

-Rich

Kevin K

iTrader: (32)

Rich.....I understand everything that you are saying and yes I know how much weight position comes into play on a chassis.....and I agree with its movement has an effect on the car. I don't have or keep documented lap times so I cant back up what I "feel" or "felt" on the track and I do understand that there is no way to have a perfect controlled back to back test....all I was talking about was what I was noticing on the track with the performance of my toy car and I wanted to see what you "physicist" had to say about it.

RichChang

Yep, no biggie. This discussion is just to the point that whoever is wondering about the gearing issue can read through what has been presented by both sides and try it out themselves if they want and come up with their own conclusions. So, it kinda doesn't make sense to keep hashing this out.

The whole thing with these r/c cars is actually feel as you have noticed. A car that feels good will be easier to drive and you'll probably be faster and more consistent. (However, a car that feels good for one person may not feel good to another.)

And, we all know a lot of this r/c car stuff is mental, too. I know I drive better for a few races after I do something to my car (such as change all the screws from purple to blue). haha!

-Rich

IMPACTPLAYR

iTrader: (7)

Rich-- how does weight distribution come into play when your talking straight line acceleration?? Don't pull the wheelspin stuff either..... BTW: a stock motor weighs about 1/3rd that of a pack of 3300's....... Also on every buggy..... every buggy except the xx-4, the motor is on average 1/8-3/16" higher than the batteries when comparing their lowest points........

RichChang

Okay, sucking me back in, temporarily.

Are you talking from exact testing experience or just going by opinion?

Geared to the same roll-out, they will straight-line accelerate the same from a stand-still, have the same top end, and hit top speed at the same time.

As is mentioned by John Stranahan in the other TC3 thread, yes, you can go to the extreme and put a 300 tooth spur on and compare it with a 50 tooth spur and there will be minor difference but the differences are due to gear mesh efficiency at the extremes. You will NOT be getting those extremes on a R/C car.

Also, 1/8th of an inch is a big difference. Since you seem to know about off-road vehicles, think about how small the washers are that you stick under the camber link ball-studs to greatly affect roll-center and handling.

Yes, a GP3300 6-cell pack (these are heavy batteries compared to Sanyo 3300s, 3000s, etc) is about 15.4 oz and a monster HP motow is 5.4. oz, so yes, a motor in this case is 1/3 the weight. You don't feel 33% is a big percentage? I sure do. (the percentage is even bigger with lighter batteries)

Okay, that is all I am saying. Maybe someone else will continue discussing this, but I am done.

-Rich

OB42TC3

Two observations here;


1. the linear velocity of the gear mesh changes when using different pinions/spurs with the same overall ratio. For instance a 100/35 is almost the same as 94/33, but the radius of the 33 is 6.9 mm and the 35 is 7.325 mm, a 6.15% change. the friction asssociated with that mesh is likely the same at the two different speeds but the linear(tangential) velocity is now 6.15% higher or lower; so while each time gears mesh the friction is the same they are meshing faster and since force times velocity is power, more power is lost at high speed(just maybe significant here, actually happens at all speeds) with the bigger spurs and pinions, there's also numerically more meshes happening for each rev of the spur. So anyway I think that may explain why a small spur seems to rev higher, it's still anyone's guess as to how much friction is involved in each mesh though and it would be really hard to measure(that's where the track comes in). Now why would the big spur accelerate better? It may have something to do with the linear velocity too as the bigger setup has a bigger radius which is closer to tangential which would mean the force transfer from the pinion to spur could be more efficient.

2. Gearboxes and transmissions in general are complex and stuff like the above usually is the fine detail that makes one better suited than another. Some factors like the friction of each individual gear mesh make the difference in efficiencies, you can't take cookbook physics and figure it out, you have to test it, then after you test it you try to figure out why it worked the way it did. If you take the frequency of the gear mesh and see how that affects the beaming mode of the armature and how that affects the conductance of the serrated e- brush.....blah blah blah

AssociatedRacer

Man you guys think to much, why dont you just race. That makes you better then staying at home at calculating stuff to see what makes the tiniest difference.

Kevin K

iTrader: (32)

I noticed the biggest change going from the stock chrome body clips to purple ones.....

I can see where moving weight around the chassis will effect straight line acceleration do to weight transfer and the energy it takes to move it...but how it translates I have no idea. All I can say is what I have noticed with my driving style and my cars.....and is there some sort of physics at work yeah there is but Im sure for every time that someone says that there is this kind of force at work there is about 5 others at work at the same time so what's really doing what I don't have the brain power to figure out all I was looking for was what someone else thought about what I thought.

Ob42tc3.....wow dude that's a lot of info to think about for a toy car....but how much of it actually means anything when Im at the track having a good time with my buddies in the pit???? ZERO but it is great to think about things like this when your at work and have nothing better to do. Its awsome that there is a site like this that we can all talk about things that are really mundane when you get down to it.....do you think Kinwald or Baker are sitting at home going over some calculation to figure out the tooth deflection of a Kimbro gear as aposed to a RRP gear I doubt it but it is fun to think and wonder about this sort of stuff.

OB42TC3

Exactly.

IMPACTPLAYR

iTrader: (7)

So let me get this correct MR. Rich....... RATIOS IS RATIOS....... HUH anyone remember the old "golden bathtub" days you know the origional stealth RC10 buggy?? Why is it that when everyone started switching to the RPM stealth tranny with a different internal ratio and then regearing their cars to acheive the same FDR if you still had the origional stealth tranny you couldn't even begin to keep up speed wise?? I's be all confused now MR. Rich?? Believe what you want, but when all of us that "think outside the box" fly by you on the straights don't blame us...LOL

yoshi

Is the Team Associated TC3 'Team' kit worth the money, with all the different parts added from the 'Racer' kit? If anyone has the 'Team' kit can you give me a brief review of what you think of it?
And if there is, what could be a suitable substitution (electric touring) at around the same price?

Thanks

DaveW

iTrader: (1)

Yes Yoshi... it is a great deal... especially since you have no need to buy any other spur gears other than the one that comes with the kit... Im getting on EBAY and selling my extensive collection of spurs... its a shame you all are reading this... cause you are spoiled and will see no need to purchase the great deal i am about to offer on all my gears!
Again... im here for the humor...
- Dave

RichChang

Let's see... I finished 2nd in the B-main at the US Indoor Champs in stock TC this past year out of 160 entries.. Yeah, I got beat by the 11 other people because they all used a smaller or larger spur than me and were able to blow by me on the straight.

Anyways, I've only been racing 4 years so the original RC10 buggy is way before my time and I have no idea what the differences are between the different trannies.

I would gander that the reason why the RPM tranny was much faster at the same ratio is because it was more EFFICIENT overall. Maybe the diffs worked better in the RPM tranny. Since the gearing was different I would guess that the motor position also moved. Maybe someone that has used those two trannies can give us some info on them.

DaveW - can I buy those spurs from you? I need them for the US Indoor Champs this year. I'm gonna TQ now! haha!

-Rich

DaveW

iTrader: (1)

Rich, i am glad there is someone else out there that can see the humor in all of this... obsession can be a destructive trait. I mean, wasnt the purpose of this site to share common info and compare with others your finds, in hopes for us all to be faster racers!?!? If i knew posting my findings on here would be critiqued by a junior high debate class grad... i would have kept my info to myself. Wait... is this obsession?! Anyways... im off to the track for a day of practice. I have mondays and tuesdays off from work... what kinda sick friggin joke is that?! So i am relegated to practice at my local track all alone. Im such a LOSER! I am however... takin all of my spurs with me to glue together as one gigantic tribute to Gundam anime. Maybe i can get creative with my absolute pinions, and create real life looking armor for this ominous robot!
Dave