Ok i just weant everyones opininon on what does the spur gear effect as far as a larger spur vs. lil spur gear and the opposite? Thanks in advance cause i know the great guys on here will probably have 2 pages of answer before i get home from work.

This has been asked many times on hear. Your going to get people to tell you that ratio is ratio and doesn't matter what size spur gear. Then others will tell you about larger gears having better eff and more power off the turns. The other side of the question is moving the motor forward and rearward in the car devolping more rear bite by moving it towards the rear more. So the answer is just sit back and wait for the fighting to begin.

I have always been told put the biggest spur on that will fit. So thats how I roll.

This has been asked many times on hear. Your going to get people to tell you that ratio is ratio and doesn't matter what size spur gear. Then others will tell you about larger gears having better eff and more power off the turns. The other side of the question is moving the motor forward and rearward in the car devolping more rear bite by moving it towards the rear more. So the answer is just sit back and wait for the fighting to begin.

LOL, I love it...
I believe, the eff. factor is so small, it can't possibly matter. I also believe a ratio is a ratio, and MOSTLY, I believe the size of the spur moves the motor around to make quite a difference in the way the car works.

Finally, size DOES matter :cool: .

ok seems size matter a lot

ok seems size matter a lot

Just ask any woman and she would agree.LOL

ok so who hasa 200t spur???/

The 100% diffrence is..................

Bigger spur= bigger pinion.... and Smaller=smaller.......the rest is all just myths...LOL

here's what I have found down here. I put a 120 supur on the car and i get smoked on the straights. put a 100 on and I am right back with everybody else. I think the smaller spur keeps the motor spun up.

ok deal

Cat-brains
What would happend if you ran a 110 spur? Just kidding


SL

the only thing I have ever been able to prove is the larger the spur the less difference in rollout there is when you change pinions. for example

If you change 1 tooth (pinion) with an 88 tooth spur this equals - 0.080 in rollout change

If you go up or down a tooth (pinion) with a 132T spur this equal - 0.053

Big difference, maybe not, but sometimes you need that half a tooth in gearing.
A larger spur helps make pinion changes smaller.

lawman what up??? I tried a 116 spur it was ok but I have always had the best results with 100's plus when everybody down here is running ultrabirds and 100 spurs it's easy to bogart the gearing!!!!!!!!! lol

speaking of bigger, enzyte is offering free trial packs while supplies last. just saw it on tv :thumbsup:

sorry i have nothing useful to add to this conversation except to try a few different sizes and see for yourself. thats what you're gonna end up doing anyway after everyone expresses their opinions. no puns intended to anyone in that sentence :wave:

I'm personally a firm believer in "Gear ratio is Gear ratio", whether 64p or 48p.

That being said, the bigger the spur, the finer the ratio change (or smaller percentage per pinion change)

Example using a very small spur, a medium spur and a large spur.

88/25=3.5200
88/26=3.3844
88/27=3.2592
88/28=3.1428
88/29=3.0344
16 percent spread in 5 gears

100/29=3.4482
100/30=3.3333
100/31=3.2258
100/32=3.1250
100/33=3.0303

13.8 percent spread in 5 gears

120/36=3.3333
120/37=3.2432
120/38=3.1578
120/39=3.0769
120/40=3.0000

11.1 percent spread in 5 gears

big track big spur. small track small spur

Like Mike has stated, this has been debated numerous times in the past. So I will post a few thing to help clear the air.


1. Leverage in the gear ratio.
You are trying to take an 1/8" diameter shaft and turn over a 1/4" axle with a 2.5" cap tire. If you can match the spur to the tire size (64 pitch 128-132 tooth) then the spur to tire size is as close to 1:1 as possible. This will allow the motor to work as little as possible to turn over the 2.5" cap tire. What you gain is efficiency off the line/take-off and off the corners. The motor does not have to work as hard to turn over the 2.5" tire when you use a taller spur gear (128ish). The downside is because the motor is working less to rotate the tire, the gear ratio will loose top end (max straightaway speed). This happens because the motor is allowed to spool RPM faster and will "top out" quicker. Intern loosing your max straight away speed.

When you go the other way with spur/pinion the effect is totally the opposite. If you can match the pinion and spur to the 1:1 size ratio you will create max top end but loose your lift off the corners. When the motor reaches it's peak RPM it will run more efficient at a 1:1 pinion/spur size. It's easier to achieve the 1:1 pinion/spur size with smaller spurs and smaller pinions. Even though you achieve the same bottom line pinion/spur gear ratio as a larger pinion spur, the smaller spur and pinion will have the closer 1:1 size ratio.

2. Leverage in the pod.
When you run a smaller spur the motor is closer to the axle. This will help "free up" the car because of the pendulum effect in the pod. The more weight you move towards the rear axle the more weight can "swing" around the corners. When choosing a larger spur the effect is just the opposite as the weight is closer to the t-plate. This can play a major effect on bumpy racetracks. If the corners are not smooth a smaller spur racecar can actually feel a tick free or loose. By going to a larger spur you can help settle the rear down. This is a fine tuning adjustment as it will not "FIX" a loose car or fix a "TIGHT" car.

Now also keep in mind every car, every motor, every track, and every driver are different. Bigger flowing tracks generally see mid range to smaller spurs 100-116. Smaller tight short tracks generally see mid to taller spurs 112-128. On carpet most choose mid to taller spurs because the tracks are usually smaller and because carpet/foams load the motor more. So taller spurs are used to allow the motor to run a bit more efficient. On larger outdoor cap tire tracks mid to smaller spurs are used because the motors top out sooner off the corners and you loose straightaway speed.

I hope this helps in answering a few of the "big spur vs. little spur" debates.

Tornado, I'd have to disagree with number 1. If you have the same pinion/spur ratio, the leverage transfered to the motor will be the same minus a very small eff lose due to the smaller gear. But it's very small considering the linear force decrease between a 116 and a 100 spur gear. I wish I could find Jay Kimbroughs explanation about this. He went into great detail about this sometime ago.

Tornado, I'd have to disagree with number 1. If you have the same pinion/spur ratio, the leverage transfered to the motor will be the same minus a very small eff lose due to the smaller gear. But it's very small considering the linear force decrease between a 116 and a 100 spur gear. I wish I could find Jay Kimbroughs explanation about this. He went into great detail about this sometime ago.

Number 1 does not talk about pinion/spur ratio, it talks about spur to tire ratio as 1:1. With what you stated "minus a very small eff lose due to the smaller gear" this goes side by side with what was stated in number 1.

Also keep in mind what I posted refered to 1:1 pinion/spur size ratio (O.D.) and 1:1 Spur/tire size ratio (O.D.) and not 1:1 gear ratio.

(Even though you achieve the same bottom line pinion/spur gear ratio as a larger pinion spur, the smaller spur and pinion will have the closer 1:1 size ratio.)

Did I missunderstand this statement, or did you missword it. What I'm saying if your running a 100 pinion and 100 spur (1:1) or a 132 pinion 132 spur (1:1) the leverage on the tire is the same, as long as the ration pinion/spur is the same.

(Even though you achieve the same bottom line pinion/spur gear ratio as a larger pinion spur, the smaller spur and pinion will have the closer 1:1 size ratio.) Correct

Did I missunderstand this statement, or did you missword it. What I'm saying if your running a 100 pinion and 100 spur (1:1) or a 132 pinion 132 spur (1:1) the leverage on the tire is the same, as long as the ration pinion/spur is the same. You could be right, but we do not run 100 or 132 pinions.

It will be harder for a motor to turn over a 100 spur than a 132 spur, that is why a 132 spur will come off the line harder/faster than a 100. It all has to do with leverage and how easier it will be for the motor to turn over the tire......

132/33 = 4.0 ratio
132 Spur = 2.063" OD
33 pinion .516" OD

100/25 = 4.0 ratio
100 spur = 1.563" OD
25 pinion = .391" OD

.500" difference between a 132 and 100 spurs
.125" difference between a 33 and 25 pinions

Looking at these numbers the 132 spur has a 1/2" OD of more leverage compaired to only a 1/4" OD added in the pinion. If both numbers were equal every time then yes a gear ratio is a gear ratio, but the numbers are always different giving different results.

Using the numbers above and a 2.5" tire:

132/33 = 4.0 ratio
132 Spur = 2.063" OD
33 pinion .516" OD

100/25 = 4.0 ratio
100 spur = 1.563" OD
25 pinion = .391" OD

132/33 = 1.290:1 pinion/spur size ratio
100/25 = .997:1 pinion/spur size ratio

132/2.5" tire = 1.219:1 Spur/tire ratio
100/2.5" tire = 1.599:1 Spur/tire ratio

The closer you get the Pinion/Spur Size Ratio the more top end. The closer you get the Spur/Tire Size Ratio together the more rip off the corners you get.

Tornado, I know what your trying to say. But lets break this down. I'll use simple numbers to help out hear. Motor devolpes 100 in/lbs torque, pinion 1/2" dia, spur 1.0" dia (1:2 ratio), 200 in/lbs are transfered to the tire. same motor, pinion 1" dia, spur 2" dia(1:2 ratio), 200 in/lbs transfered to tire. I know this isn't expressing the formulas, but thats the facts, less the eff loss of the smaller spur gear which is vary small, less then .01%. I have been down this road before, so I ask around at work and get the same answer, from all the eng. http://www.ebco-aerospace.com

Tornado, I know what your trying to say. But lets break this down. I'll use simple numbers to help out hear. Motor devolpes 100 in/lbs torque, pinion 1/2" dia, spur 1.0" dia (1:2 ratio), 200 in/lbs are transfered to the tire. same motor, pinion 1" dia, spur 2" dia(1:2 ratio), 200 in/lbs transfered to tire. I know this isn't expressing the formulas, but thats the facts, less the eff loss of the smaller spur gear which is vary small, less then .01%.

Question:
When racing at the Snowbirds sized tracks why do most 4-cell mod cars run 120, 124, or 128 spurs and not 96, 100, or 104 spurs if a gear ratio is a gear ratio?

Answer:
It's not the lack of pinion choices it's more rip off the corners!

Why:
More leverage so the motor can transfer the rip easier/faster.

I have been down this road before, so I ask around at work and get the same answer, from all the eng. http://www.ebco-aerospace.com

I have as well www.precisionracingsystems.com (http://www.precisionracingsystems.com) The difference is we race and manufacture R/C Racing Gears. EBCO-Aerospace does not! lol

DAMN, I should have used a 128 spur instead of the 104 spur that I used to take second at snowbirds, the last time I attended, if only I knew. I'm glad your backing up your statements with opions instead of facts based on physics.

DAMN, I should have used a 128 spur instead of the 104 spur that I used to take second at snowbirds, the last time I attended, if only I knew. I'm glad your backing up your statements with opions instead of facts based on physics.

Maybe your car was a bit tight, loose, or you were getting some wheel spin. Smaller spurs will help as stated above in earlier posts (leverage)!

Now when you start getting "SMART" it's time to quit. This was going fine until your last post.

"This has been asked many times on hear. Your going to get people to tell you that ratio is ratio and doesn't matter what size spur gear. Then others will tell you about larger gears having better eff and more power off the turns. The other side of the question is moving the motor forward and rearward in the car devolping more rear bite by moving it towards the rear more. So the answer is just sit back and wait for the fighting to begin."

Taken from Page one 2nd post.

Yes, you do mfg R/C racing gears. But you opion isn't based on any hard facts just impressions at the track. The last post was alittle out of line. but the prior one was fine IMO. The simple numbers where ment so every one could follow along, not directed towards you.

I think what you missing, when you talk about "Spur/Tire Size Ratio" is that your using a larger pinion gear to keep the same rollout. In doing so the force being exerted to the spur is less, due to being farter away from the center of the motor shaft. I can even tell the future.

...I CAN see what the socalled "Leverage Factor" could be a true factor. In this small of a scale, a quarter inch is a huge amount of leverage if you scalled it up.

I guess if you think about it in full size terms, stick a 3 ft. long bar across the axle of a full size car, measure the amount of torque load it takes to turn that wheel. Now, use a 10 ft. bar to turn the same wheel and it takes about 1/3 the torque force. (We call that Torque Leverage) Just like putting a cheater pipe on a wrench or ratchet to break a tight bolt loose.

Once the thing is moving, I could see where the smaller gear could pull a little harder on the amp load, even though the ratio is the same. Although, I've never seen or felt any speed change between small and large spurs, and have always been able to back up lap times with either (But, I run MOD most of the time and power isn't a problem...STOCK this may have some benefit)

ok guess im going just go to the track sunday and see how it works think im try a 96 and a 120 and worh for there the track im running right now is a large 350ft runline semi banked asphalt track

You can use all the equations you want ...But if you put a 124 128 132 spur gear on a car it will come off the corners and offf the lin better ...If you run a 100 96 88 or whatever the car willl carry more straight away speed because the motor will spool up in rpms...A larger spur will also help a tight car from center offf the corner ...Where as a small spur will compound the problem .....

HUMPTY, I agree with the last part.

Swtour, in your example your appling the same force to the lever arm, just farther from the work. In the case of the pinion the force isn't the same the farther you get away (larger pinion)

WOW...this is better than the battery disscusion from yesterday!!

EA

EA I can hear you laughing in CT.

Oy Vay ! Lol

Mike says Swtour, in your example your appling the same force to the lever arm, just farther from the work. In the case of the pinion the force isn't the same the farther you get away (larger pinion)

Mike, I'm actually NOT applying the same force to the "hypothetical lever arm",

If at .7500" from axle center, it takes 2 grams of force to move the axle, then at 1.500 from axle center, it should only take 1 gram of force.

In all the examples, the gear ratio is the same ( use a 4:1 ratio for kicks) The MOTOR is going to try to put out the same FORCE w/ either size spur.

Now, where I guess my question is...

You GAIN leverage on the SPUR, but in doing so...you LOSE it on the MOTOR end...so which is more important?

here we go

I thought everyone knew the spur gear doesn't matter. You just need a 30 tooth pinion because a 30 tooth is the always the fastest.

Swtour, "You GAIN leverage on the SPUR, but in doing so...you LOSE it on the MOTOR end...so which is more important?" That's my point exactly. you lose the same amount you gain on the other. keeping the same ration will produce the same force.

Mike says

Mike, I'm actually NOT applying the same force to the "hypothetical lever arm",

If at .7500" from axle center, it takes 2 grams of force to move the axle, then at 1.500 from axle center, it should only take 1 gram of force.

In all the examples, the gear ratio is the same ( use a 4:1 ratio for kicks) The MOTOR is going to try to put out the same FORCE w/ either size spur.

Now, where I guess my question is...

You GAIN leverage on the SPUR, but in doing so...you LOSE it on the MOTOR end...so which is more important?

You gain more on the spur:

132/33 = 4.0 ratio
132 Spur = 2.063" OD
33 pinion .516" OD

100/25 = 4.0 ratio
100 spur = 1.563" OD
25 pinion = .391" OD

.500" difference between a 132 and 100 spurs
.125" difference between a 33 and 25 pinions

.500/.125 = 4.0 ratio

1+1=2

I can do math too! lol (and I didn't even need a calculator)

I feel so grown'd up!

I am just play'n and havin' fun no harm intended.

a gear ratio is a gear ratio is a gear ratio. The only thing larger gears give you is more rotating weight.

a gear ratio is a gear ratio is a gear ratio. The only thing larger gears give you is more rotating weight.

I agree with this,,

Also bigger = Motor farther back
Smaller = Motor closer to the center

yea and on my adreanaline 10 the further back the motor is the lower it sits in the car

I agree with this,,

Also bigger = Motor farther back
Smaller = Motor closer to the center

Isn't it the other way around?

Smaller = Motor closer towards the axle
Larger = Motor closer to the t-plate

I am no pro but I don't think you can get the appropriate ratio with a 120 spur on a 350' runline track.

120 spur a 35 pinion = the motor barely fits in the pod (L4)

Isn't it the other way around?

Smaller = Motor closer towards the axle
Larger = Motor closer to the t-plate


My bad, not thinking straight, Your right

Big spur, short track. Small spur, big track. Big track tight turns, in between spur.

yea i have to get a set of extanded pod plates