Pedmar007

Can anyone say if using a higher fdr helps with an onroad 1/10 TC kit that's on the heavy side, let's say over 1400g? I'm asking because I have a kit that's over 1400g and the fdr is 4.61 and a guy with a lighter kit of 4.68 fdr both using same motor brand but a 1 model difference. He was pulling on me and I was thinking if in having a heavier kit, to use an fdr higher than the 4.61 if that would help stop being closed on. Basically asking if using a high fdr would help get a heavy kit around better, if there wasn't much to do to reduce the weight that wasn't already done.

glennhl

iTrader: (16)

F=MA (A=F/M} is not your friend when you have the heavier vehicle. You can try to go to a higher FDR, but it will lower your top speed. I would also try a lower FDR to see if picking up top speed at the end of the straight helps out.

Dan the Man

iTrader: (41)

Even though you have the same model motor, you might find yours is less powerful.

Have you tried your friend's motor in your car?

Pedmar007

I'm using 48p gearing and I'm thinking of switching to 64p where I was able to work out a gearing pair that gives me a similar fdr with same top speed but with a slightly higher fdr. So I will try it out and see the result. I have the newer motor.

SmilingEel

You can try to go to a higher FDR, but it will lower your top speed. I would also try a lower FDR to see if picking up top speed at the end of the straight helps out.

AngryRog

iTrader: (20)

Timing can be a factor as well.

SteveM

iTrader: (165)

I have never heard of anyone adjusting gearing based on a car's weight. In the USGT or Stock Sedan class, I target an FDR of 3.8 and adjust from there. On a small tight track with short straights I would adjust up and on a larger more open track with longer straights I would adjust down. I prefer 64P gearing as it allows for finer FDR changes.

Bry195

well what is speed? its certainly rpms isn’t it? would it make sense that the sooner you get to those high rpms the better? well then its acceleration. some combination of a force acting on a mass is acceleration. well what creates this force? its the motor but its rotary so we call it torque. if you plot motor torque on a curve what does it look like? it looks like a bell. at the peak of torque you accelerate more than any other point on the curve so wouldn’t you want to make sure that the motor spends most of its time or the average of its time on this peak?

is it better than using a stop watch and adjusting gearing. no. but it can be better. it can also confirm your stop watch method. it can tell you if you did something wrong as well. this peak on the curve is different on all motors. you can still find it if you make enough gearing changes. after you apply these calculations a couple of times and confirm the car is doing what is expected you will hit the peak of the curve the first time every time.

but is one method better than the other? if the goal is to run the quickest lap in a vacuum then both are equal with the minor exception of saving a little time (sometimes). but understanding acceleration and speed isn’t the end of the understanding. if you get the gumption to understand the calculations you are only a couple variables away from understanding efficiency and heat. its also the beginning of understanding how timing works and that over timing to weaken the magnetic field is not the ticket to generating more power. there is only 1 perfect timing mark position for a combination of gearing and track distance.

you are using all of these simple measurements and formulas when you do the stop watch setup method and check temperature. if you are careful you can methodically achieve the same results until you can’t. If you have the motivation to understand it you can or you can ask someone who does. one isn’t better than the other until you encounter something you don’t understand and then you can potentially solve your problem if you know both.

there is 50 ways to remove a stripped screw. one way isn’t better than the other. the result is. you may only need one method....until you need 2.

SteveM

iTrader: (165)

All this blah blah blah to say nothing at all and provide no advice for the OP. Hopefully you'll have some useful advice to provide and can do so using proper punctuation.

Bry195

I quoted you because I was responding to you. Your comments were the subject. Proper sentences communicate a concept, period. That’s a little punctuation humor for people who understand punctuation and subjects at the same time. I fixed your punctuation but it didn’t fix the connection of your concept to mine. There is nothing wrong with just “doing”. There are people doing all kinds of things each of us hasn’t seen before. It doesn’t mean there isn’t a reason or others who have seen the opposite. it also doesn’t mean you have to agree with it. If your comments lead someone to an opinion such as, understanding is a waste of time, then my response is, I disagree.

I provided a ton of advice to the op. The problem is he asked a question that requires someone to know where peak power is at the motor shaft. He can run the gear change game and watch how his times change but I just assumed allot of information you didn’t provide because I guessed at what you were saying. Alternatively, he can understand how to make the car faster with a higher mass by understanding how to speed up the chassis by looking at it from the motors perspective.

Jochim_18

iTrader: (10)

Here is my answer go out on the track and practice with purpose. You can have the same gearing with practice you will be faster next time out. People sometimes trying to get the speed when on a race you missed the turn by a mile. On Spec racing keeping your lines tight on the apex will reduce your lap time and having a proper setup car.

SteveM

iTrader: (165)

What and where have you provided all this advice? I do not see anything meaningful from you in this thread.

Bry195

I assumed so. That’s why I tried to simplify F=MA. if you have a larger mass then you need more force to accelerate it. there is a single point on a motor curve that delivers the most force. Set your gearing to that and you get the most acceleration. Miss that point by 10% and you could be off on your acceleration by 20%. I thought it was helpful of me to simplify Glenns advice and at the same time disagree with you in a way that maybe you or others who haven’t seen things like this might consider it when they run into a problem to solve.

If you had said you understand F=MA and it doesn’t apply....well thats different. You said you never see people doing stuff like that. I have and do. it doesn’t mean you are wrong or less in any way. it means that someone who wants to understand more doesn’t look in the wrong place when gearing swaps don’t get them what they want.

seems on topic to me. What is off topic is continuing to re-summarize my response to your comment. You are welcome to tell me I’m wrong. You may choose to tell me why but its going to get pretty boring if I continue to respond to “you contributed nothing”. I explained the fundamentals of getting a heavy car to go as fast as it can with a given motor. Actually, Glenn explained it. I just simplified it.