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Bigger Spur Or Smaller Spur?

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Bigger Spur Or Smaller Spur?

Old 05-20-2024, 10:01 AM
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Originally Posted by DirkW
Sounds like what I said at the end of my post.


Viola? Well, at least not the "walla" I see so often. Not quite there yet, though.
Sorry didn't see that you had posted that already and thank you for correcting my spelling of Voila! But then again, maybe I like large violins.
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Old 05-20-2024, 10:01 AM
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Originally Posted by oldfool
Even if it works, I hate this idea.
Don't knock it until you try it. I agreed with you before I tried it. I had always had a hard time getting a good mesh with 64 pitch gears. That's why I use 48 pitch in my touring cars. But I run 64 pitch in my 1/12 scale cars. A good friend told me about this trick and I couldn't believe how every time I had the correct amount of backlash.
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Old 05-22-2024, 10:43 AM
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Originally Posted by geeunit1014
A bigger spur= more acceleration/ less top speed. A smaller spur= more top speed less accl.
Thank You!!
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Old 05-24-2024, 02:27 AM
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Originally Posted by DirkW
Sorry you're just wrong. But since you probably won't ever check your own math (properly) or listen to people telling you, I'll quickly write something up for everyone. I'll use a 90/30 combo as baseline.

I'll show a few examples below:

a common mistake is if you adjust both, spur and pinion, in the same direction but only by one tooth each, with that your ratios change:
{+1 /+1}
93/33
= 2.81818... : 1
92/32 = 2.875 : 1
91/31 = 2.935483... : 1
90/30 = 3.0 : 1
89/29 = 3.068965... : 1
88/28 = 3.14285... : 1
87/27 = 3.22222... : 1
{-1/-1}


What you actually need to do is to adjust both spur and pinion in the same direction (both up or both down), but in the correct overall ratio (here 3:1): this is how the ratio stays constant:

{+3/+1}
99/33 = 3.0 : 1
96/32 = 3.0 : 1
93/31 = 3.0 : 1
90/30 = 3.0 : 1
87/29 = 3.0 : 1
84/28 = 3.0 : 1
81/27 = 3.0 : 1
{-3/-1}


Now if you only ever change one side, in this example only the spur, same pinion - your ratios change:
{+3/+0}
99/30 = 3.3 : 1
96/30 = 3.2 : 1
93/30 = 3.1 : 1
90/30 = 3.0 : 1
87/30 = 2.9 : 1
84/30 = 2.8 : 1
81/30 = 2.7 : 1
{-3/-0}


Same basic thing happens when you change the pinion only: your ratios change:
{-0/-1}
90/27 = 3.33333... : 1
90/28 = 3.21428... : 1
90/29 = 3.10344... : 1
90/30 = 3.0 : 1
90/31 = 2.90322... : 1
90/32 = 2.8125 : 1
90/33 = 2.727272... : 1
{+0/+1}


Everyone still with us? OK, Now I will make the changes to both, spur and pinion but in opposite direction and behold: your ratios change even faster - they do not remain the same ratio.
{+3/-1}
99/27 = 3.66666... : 1
96/28 = 3.428571... : 1
93/29 = 3.206896... : 1
90/30 = 3.0 : 1
87/31 = 2.806451... :1
84/32 = 2.625 : 1
81/33 = 2.454545... : 1
{-3/+1}


Please 1spunspur , provide a single example for your claim that you keep the same ratio when you adjust the spur up and pinion down, or vice versa. Just one example of such adjustment where this works out in your math.


------------------------------

Different from all that (and what some people may confuse): there is one thing that actually stays the same (at least in theory) when you adjust spur up and pinion down (or vice versa) by the same amount of teeth, but it's not gear ratio: the motor position does not change. So, for example if you use 90/30, 80/40 or 100/20 - you will have very different ratios with each, but you should (at least in theory) be able to put all of these gear combos in without ever having to change motor position or even adjust gear mesh at all (manufacturing tolerances may still apply).
finally you agree with me. The spur and pinion are to be changed as a set. Check your post, 3:1
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Old 05-24-2024, 03:47 AM
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Originally Posted by 1spunspur
finally you agree with me. The spur and pinion are to be changed as a set. Check your post, 3:1
To change as a set you have to increase both or decrease both. You said increase one and decrease the other.
Originally Posted by 1spunspur
Spur and pinion are a set. So for example if you want to achieve a 4 to one gear ratio you may run a big spur gear with a smaller pinion to get smoother acceleration out of the turns. but for more speed quickly you should run a smaller spur with a bigger pinion and still maintain the same gear ratio. Calculate your gear ratio, number of teeth on your spur divided by number of teeth on your pinion.
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Old 05-24-2024, 05:27 AM
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Originally Posted by gigaplex
To change as a set you have to increase both or decrease both. You said increase one and decrease the other.
Exactly.

1spunspur you made the exact opposite claim from what I've shown. And you were so confident that you even told other people that their math was wrong and they'd need a new calculator, etc. over your claims... So please do not pretend now that you said it differently all along. The least you can do is either admit that you were wrong all along or provide an example where your claim works that you can maintain the same ratio with either spur or pinion getting smaller while the other gets bigger.

Remember, this is the part you claimed would keep the same ratio:
Originally Posted by DirkW
{+3/-1}
99/27 = 3.66666... : 1
96/28 = 3.428571... : 1
93/29 = 3.206896... : 1
90/30 = 3.0 : 1
87/31 = 2.806451... :1
84/32 = 2.625 : 1
81/33 = 2.454545... : 1
{-3/+1}
Go ahead and use your own numbers to show us - or admit you were wrong.
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Old 05-24-2024, 08:23 AM
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Originally Posted by DirkW
Exactly.

1spunspur you made the exact opposite claim from what I've shown. And you were so confident that you even told other people that their math was wrong and they'd need a new calculator, etc. over your claims... So please do not pretend now that you said it differently all along. The least you can do is either admit that you were wrong all along or provide an example where your claim works that you can maintain the same ratio with either spur or pinion getting smaller while the other gets bigger.

Remember, this is the part you claimed would keep the same ratio:

Go ahead and use your own numbers to show us - or admit you were wrong.
could you guys delete wrong info? In the hopes that someone new get wrong info and possible make their learning process more difficult. Can't even count the amount of times I seen people get discouraged because they listen to the wrong info.
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Old 05-24-2024, 08:37 AM
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The original question was answered in the second post, and the OP thanked him for his answer in the third post. Everything after that post should be deleted.
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Old 05-24-2024, 08:49 AM
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Originally Posted by Mac The Knife
The original question was answered in the second post, and the OP thanked him for his answer in the third post. Everything after that post should be deleted.
Thread is originally from 2005 and was revived a while ago by someone who at least tried to search for the topic. Had that not been done, he'd simply have started a new thread instead and some people would still insist on putting wrong information in it.
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Old 05-24-2024, 08:51 AM
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We can keep the correct math, delete the misinformation and close this thread. Any more replies will likely be just more bickering.
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Old 05-24-2024, 03:37 PM
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people are talking about stuff i don't like, we should lock the thread
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Old 05-24-2024, 04:08 PM
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Originally Posted by skypilot
people are talking about stuff i don't like, we should lock the thread
2/2=1
3/3=1
4/4=1
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Old 05-27-2024, 06:41 PM
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Larger Spur with larger pinion to get more overall torque,
while maintaining the same gear ratio.
​​​​​​​

https://www.amainhobbies.com/xray-64...83022?v=978898
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Old 05-27-2024, 06:47 PM
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Whoever wrote that is wrong, you do not get more torque by making both gears bigger while maintaining the same ratio.
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Old 05-27-2024, 07:24 PM
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Originally Posted by gigaplex
Whoever wrote that is wrong
I thought it was a strange claim. Wonder if it's an Xray or AMain chart.

I guess it could be said the smoother mesh would give more torque.

And there was a time when heavier pinions made more torque.
People would even make a flywheel to fit on the pinion.
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