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Post by dave632 on Mar 28, 2017 13:46:13 GMT -7
How much difference is there between 3G & 4G chassis, also how much difference does dropping from 18-20 V make? Mike I thought that was a great question and I went to work on it. I took my 2 fastest Street Outlaw 4G cars and my #4 & #5 PSO cars, from my in house top 10 list, all these are similarly prepared. I have my own in house top 10 PSO list now, more on that at a later date. I used my #4 & #5 cars because I have a much larger selection of PSO type cars. A side note the Summit Camaro smoked it's arm at the Winter Nats, it has a new arm in it making it run quicker than before. Here are the results: The 3G #4 car, white and blue 67 firebird, against the 4G Jungle Jim Camaro running at 20 V. 3G has about .1 ET and 4 mph advantage  3G vs 4G 20V
Here the #5 car, yellow 55 Chevy, against the silver Summit 4GCamaro. The 55 has about a .07 advantage + about 3.5 mph.
 3G vs 4G 20V
Dropped the voltage down to 18V with the same cars:
Again the 55 has about .07 and 3+ mph.
 3G vs 4G 18V
The Firebird shows a similar difference at 18V over Jungle Jim and his 4G Camaro. About .09 and 4 mph.
 3G vs 4G 18V
ET difference between 18 & 20V was about .04-.05 for all the cars, mph was down about 1.5 for all the cars.
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Post by bluesguy on Mar 28, 2017 18:35:05 GMT -7
Hey Dave,
Thanks man, I see that the 4gs jump out and lead in et at the 60ft mark, then start to fall behind before the 330, and then the pso is pulling away the rest of the way. Good info, appreciate your help.
Mike
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Post by dave632 on Mar 28, 2017 18:44:35 GMT -7
I did not use my fastest 3G cars since my selection of 4Gs is so slim. The margin would have been bigger if I used my fastest. The 57 Nomad has recorded times as low as .550 on my track when it is in a good mood.
It was a good comparison as we all knew there was a difference but I have never saw a direct comparison.
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Post by ecbill on Mar 29, 2017 18:23:41 GMT -7
Hey Dave, Thanks man, I see that the 4gs jump out and lead in et at the 60ft mark, then start to fall behind before the 330, and then the pso is pulling away the rest of the way. Good info, appreciate your help. Mike Good observation. Sounds like gearing itself may be the biggest difference. Do you think the little arm gear maybe the main problem? |
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Post by bluesguy on Mar 29, 2017 19:27:53 GMT -7
Hey ecbill,
Yeah definetly, the 4g has the 9t arm pinion, the t-jet, afx & mag trac all use 14t. I'm not sure what the tooth counts are on the top plate of the 4g.
With that info we could figure the actual 4g gear ratio. If any one knows and wants to share that info that would be cool.
I'm really trying not to have to count the gear teeth.
mike
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Post by dave632 on Mar 29, 2017 19:49:33 GMT -7
I have never figured out the actual final ratio but the 4G were originally made for the large dragster tires which would have made the final distance traveled by one revolution of the rear wheel, with the dragster tire, probably longer than a typical 3G.
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Post by SKR on Mar 30, 2017 5:47:38 GMT -7
good topic fellas. I think its the motor pinion followed by the big cluster gear as the main cause for a high gear ratio. Similar to riding a mountain bike when you switch to the smaller front gear and bigger rear gear when going up hills. How the rest of the idlers come in to play is beyond me so I took on the daunting task of gear count to see what you math wizards can come up with.
9T Motor pinion, First gear 26T Second gear, big idler 20T 3rd gear, Idler 20T 4th gear, Idler 12T attached under 4th idler 18T Axel crown gear |
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Post by Eagle Racing on Mar 30, 2017 8:46:43 GMT -7
Yep, counted each and ever one of them gear teeth myself to Sam. Here is a link I use maybe it will help. virtualgarage.net/Automobilia/Miniatures/SlotCars/Tips/ModelMath.jhtmlUse the Aurora Step Down and the Distance Traveled calculator. The way I use it is the two 20T gears cancell each other, so I input the larger 26T gear as the cluster. However if it makes you happy to input the 20T knock yourself out. |
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Post by dave632 on Mar 30, 2017 12:58:38 GMT -7
Here is what I calculated.
On the 3 gear the armature drive gear divided into the idler = 1.714, the idler and the top of the cluster gear are the same so they cancel each other out. The 12 tooth pinion divided into the crown = 1.25. 1.714 x 1.25 = 2.14 as the final drive ratio.
The 4 gears are tougher since they have an extra idler gear of a different size. 26 idler divided by the 9 tooth armature gear = 2.88, the 26 tooth idler is then connected down to a smaller 20 tooth idler which drops the ratio dividing by 1.3 to a 2.21. Then the cluster gear cancels out the 2nd idler as the have the same 20 tooth count. This is then multiplied by the final pinion crown gear ratio of 18 divided by 12 or 1.5 which gives us 1.5 x 2.21 or 3.32.
So the final ratios between the 2 are 2.14 for the 3 gear and 3.32 for the 4 gear. Now you have to add tire diameter into the mess. If you are running a basic .474 3 gear tire vs a dragster tire of about .610. 3.14 x .610 = 1.91. 3.14 x .474 = 1.48. This indicates that the smaller tire will travel about 23 percent less than the .610 in one revolution. Taking 23 % off the 3.32 ratio will bring it down to about 2.55 which would make it only slightly lower in ratio to the 3 gear. If you start using smaller tires on the 4 gear this will make the ratio a lot lower for the 4 gear. If anybody can figure this out better please go ahead and do so.
Now that my head hurts a much simpler way to do this is to mark the tire, turn the tire one full revolution and count the times the armature pinion spins. This is what I used to do with full size cars when we did not know the ratio and you can get pretty close to actual gear ratio.
I got 1.75 on the 3 gear and 2.75 on the 4 gear. Not exact but close enough, there is also some slop that you cannot account for when using this method but I cannot figure why it is about 20% off from the calculated method unless my calcs are off.
Thanks for the brain buster Eagle & SKR.
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Post by bluesguy on Mar 30, 2017 13:59:55 GMT -7
Thanks guys,
Appreciate the help.
m
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