Seeking help with gearing and battery...

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bull8042

bull8042

Active Member
Messages
73
Location
Fort Mill, SC
I have a 2-month old Savage XL Nitro..... sort of. Currently I am running Innovative-RC LCG Extended 6mm front, 1" rear TVPs, center tank mod from IRC, Axial 40-Series Beadlocks, and Proline 3.8 Trenchers, Boca ceramics, etc.
I am making the switch to the Tekin 1/8 RX8 Brushless System with 4038 Brushless 2250kV Motor and will be converting the 3 spd trans to a single speed using the Flux 44t idler gear HPI-100905.
The diffs are factory-ratio XL BP diffs. I already have a 47t steel spur gear set HPI-86806 as well as a 49t and 52t. When I run these numbers through the online calculator, the top speed is coming in around 15 - 24 MPH. So I am concerned that I am missing something, big time. Having scoured this site and a few other resources, I am not content that I have an answer that I can rely on.
I am into backyard bashing and tearing up the neighborhood for the most part. I'm looking for good performance, but don't want to push the limits to the point that I risk smoking the ESC. Soooooo....

1) I am thinking 5000 - 6000mAh 4S will be sufficient. What is the best way to get 4S, a single 4S pack or 2 x 2S packs wired in series?

2) Can anyone recommend an optimum tooth count for the pinion and spur gears considering the information detailed above?

Thanks guys,
Bull
 
bull, ive given this advice a lot and stand by it. the weight of a savage is a huge factor to consider when running brushless and selecting gearing.

i highly recommend sticking with the stock gearing 20/44/44 and stepping up the voltage (good quality packs) to 5s.

here is a decent estimate of top speed on 5s with your set up:

bull8042.jpg


the highest i would ever consider going on a flux pinion is 22t, but i run 20t and the all around speed is ballistic. over-gearing a flux just a little can very easily end your bash session with a BC fire extinguisher.

& yes, 5Amp is plenty. my 6.5A hyperion 3s doesnt fit in the battery box.
 
frddyj said:
bull, ive given this advice a lot and stand by it. the weight of a savage is a huge factor to consider when running brushless and selecting gearing.

i highly recommend sticking with the stock gearing 20/44/44 and stepping up the voltage (good quality packs) to 5s.


the highest i would ever consider going on a flux pinion is 22t, but i run 20t and the all around speed is ballistic. over-gearing a flux just a little can very easily end your bash session with a BC fire extinguisher.

& yes, 5Amp is plenty. my 6.5A hyperion 3s doesnt fit in the battery box.
Click to expand...

That was the biggest concern. Fire/smoked ESC = BAD!
I will order a 20t pinion and a 44t spur and go from there. I will also go back and run the numbers on that calculator again. For some reason my results came back with about half that speed.... Weird.
Also, you say the 5000mAh is plenty at 5S. But you didn't clarify, are you doing a 2S + 3S in series? Or a single 5S?
 
the calculation i ran was with a 47t but yeah a stock 44 would work killer.

the speed is much higher on the calculator i ran because i used 18v (should have really been 18.5) and on 4s you woulda used 14.8v.

this represents a difference of a difference of 3.2v & 7200 rpm of the different voltage scenarios.

in actuality, you will get the following rpm from that motor given the respective voltage:

4s = 14.8v x 2250 = 33,300 rpm
5s = 18.5v x 2250 = 41,625 rpm
6s = 22.2v x 2250 = 49,950 rpm

5s is the sweet spot between saying "yeah this truck is great" & "OMG" :spiderman:
 
Last edited by a moderator:
Great, that is what I needed to know. Thanks freddy, I really appreciate the clarification.
 
If I could trouble you one more time, would you have a preference between these two?
Turnigy nano-tech 5000mah 2S 25~50C LiPo Pack
ZIPPY Flightmax 5800mAh 2S1P 30C
I like the Hyperion, but I just dumped over $500 on this conversion and it hurts to think about spending $200+ more on two Hypers.
Maybe cheaping out here is stupid though.....help!
 
bull8042 said:
If I could trouble you one more time, would you have a preference between these two?
Turnigy nano-tech 5000mah 2S 25~50C LiPo Pack
ZIPPY Flightmax 5800mAh 2S1P 30C
Click to expand...

I might be wrong about this, but I think that they are the same company..... I did see a review on a few lipos and if I remember right they said Zippy is now Turnigy. Not a 100% on this.......
 
sorry bro, i don't have any experience with those packs. maybe start a separate thread with that question, I'm sure some guys who know whats up will chime in.



i had a convo with someone who said the nano were good, I'm trying to remember who that was. maybe he'll chime & help out.
 
Last edited by a moderator:
OK, thanks guys. I ordered a Turnigy nano-tech 5000mAh 3S 25~50C LiPo Pack and a Turnigy nano-tech 6000mAh 3S 25~50C LiPo Pack. (The 6000mAh 3S is out of stock at the moment. I will order it later so both packs will have the same mAh rating.)
So I will run these and see how they do. Perhaps I will be able to answer my own questions in a few weeks.
 
bull8042 said:
OK, thanks guys. I ordered a Turnigy nano-tech 5000mAh 3S 25~50C LiPo Pack and a Turnigy nano-tech 6000mAh 3S 25~50C LiPo Pack. (The 6000mAh 3S is out of stock at the moment. I will order it later so both packs will have the same mAh rating.)
So I will run these and see how they do. Perhaps I will be able to answer my own questions in a few weeks.
Click to expand...

**EDIT**
DANG! No edit button to cover my stupidity. I ordered the 5000mAh 2S and 6000mAh 3S LiPos. The 6000mAh 2S is out of stock.....
 
TripleSix said:
You are not planning to run those together for 5s are you? You need to have matching mah, and c rating.
Click to expand...

+1 six. if you run 2 different Mah you'll trick your LVC and over-discharge that 5A pack which will lead to a fireball.
 
TripleSix said:
You are not planning to run those together for 5s are you? You need to have matching mah, and c rating.
Click to expand...

bangwall.gif
rant.gif


Sorry, I can't seem to find my "kicking myself in the a$$" smilie....
I knew the different mAh rating were throwing a mental flag for something, but I glossed over it to hurry and get the order in.
 
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