Q. about gearing, and some more questions

[Aero]

e-revonut> thanks for clarifying :)

briang> thanks ditto :) i never use rollout, i know those calculator pages too, the way i see it, rollout is to maintain a rel.ship between torque and speed? i did some reading and some things look odd. like on this page:
http://www.rcuniverse.com/forum/m_3255405/tm.htm

where its written "Question 1: What size spur gear should I run? What about the pinion gear?
Well……. When selecting the spur gear and pinion gear size, you need to
understand that there is a direct ratio between the tire circumference (referred
to as roll-out) and the final drive ratio. That ratio, in most cases, should be
as should be as close to 1 to 1 as possible. 1 to 1? What? By a 1 to 1 ratio, I
am referring to one revolution of the tire to one revolution of the motor. In
doing so, we do our best to maintain the overall efficiency of the motor by
keeping it in the ‘Sweet Spot’. Here’s how..."

the bolded quoting sounds like zero gearing to me ? also, he mentions efficiency in percentages, as for rollout ratio, why is efficiency even in here, no matter the size of wheels and tires..the drivetrain is geared. i would assume that zero gearing would have the least in-efficiency. not that it matters, does it ? yes, a much-geared drivetrain would have some inefficiency, but that doesnt mean one should try to go with the least geared drivetrain does it ?

and a quote on the efficiency:

"We can check our overall efficiency by dividing the
roll-out by the final drive ratio. In this case, the 10.2101 roll-out, and the
10.44:1 final drive ratio means that we have less than a 3% total loss in
efficiency. In other words, the tire turns 0.977 times, for every 1 revolution
of the motor. Generally, it is best for your motor to gear your vehicle within a
+ or - 10% margin. ( In the case of this formula, +1 to -1 is an acceptable
margin.) "

..i dont see how that efficiency is logic. would it be 'top speed' instead of efficiency ? it may mean that 3 % of speed become 3% of torque or vice versa, as thats all a rollout is ?

where does the idea behind rollout 1:1 inherit from, i checked my esavvy for rollout and seems it IS pretty close to 1:1 (inch) rollout with the stock 20t pinion, all stock setup. so i figure rollout is good for defining a speed/torque.

but, speed/torque is 'defined' by the motor ? if one slaps a torqier motor on, gears less in drivetrain, the rollout is eventually changed. so using briang's calculator my rollout now is 1.8:1, i dont see how that can be 'inefficient'. on the post from rcu, i should take my final drive gearing (10.2) and deduct rollout (18.5") - now where on earth does that bring me..

i did check the rollout on stock stampede vxl too, rollout is pretty close to 1:1. Now, with 3s and spur/pinion changes, the rollout is then 2.2:1

i dont think there's such a think as inefficient rollout. ?

btw, i find it more useful to look at the 'axle torque' using briang's calculator. less axle torque= more top speed. and then eventually using a temp meter

thanks for replying guys i appreciate it. i will read up on the posts now ;)

[suicideneil]

..i dont see how that efficiency is logic. would it be 'top speed' instead of efficiency ? it may mean that 3 % of speed become 3% of torque or vice versa, as thats all a rollout is ?

The 1:1 rollout ratio is just a good guideline to try and prevent beginners from entering unrealistic numbers in order to create a speed machine from unsuitable components. More advanced users will know that they can use a taller overall gear ratio if their motor, esc and batteries are suitable, but some young people who are new to the hobby usually make their post something like "how do I make my truck do 100mph?"; if you dont give them guidlines to follow, then they will only end up cooking somethign expensive without ever figuring out why. 1:1 is close to what most stock trucks have, such as your esavage and the brushed emaxx for example.

but, speed/torque is 'defined' by the motor ? if one slaps a torqier motor on, gears less in drivetrain, the rollout is eventually changed. so using briang's calculator my rollout now is 1.8:1, i dont see how that can be 'inefficient'.

Bear in mind the thread on rcu is 5 years old- there are simpler equations to follow these days- or just use the gearing calculator, saves the effort.

As I mentioned before, when you use a more powerful motor, esc and batteries, you can ofcourse gear higher and this causes the roll out ratio to stray away from the 1:1 ratio which is optimum for a lower powered stock setup. Its not so much about there being an inefficient rollout ratio, its more to do with being efficient for a certain setup; a sensible 40mph setup will be much closer to 1:1 vs a speed-run setup which is geared for 70mph for example.

I wouldnt get too bogged down worrying about rollout ratios, its more important to get an understanding of which esc, motor ,battery & gearing combos are best for any given scenareo & vehcile; years of reading and research helps with that, like 'learning on the job' at your work place..

[Aero]

thanks for the explanation suicideneil. hm does yout avatar come from that game 'my lil bastard' ? well i didnt see that rcu thread was that old i do think its a bit misleading. as im more mislead than stupid of coz

I see the point in relating the 'rollout' to switching wheels, and also once i had a telemetry, to calculate speed (then i saw the interest in rollout). when thinking over it, both an esav and a pede has a stock 1:1 rollout, then that lead me to believe those trucks are designed like that. despite using imperial(inch) the 1:1 ratio seems to 'coincidentaly' ? work as a 1:1 guiding. why that is ? So it's just like that, the rc manufacturer puts on some kind of wheels (diameter) that relate to the gearing - or vice versa. well interesting. Because, the esav has brushed motors, the stampede has brushless motor.

im suspecting it has to do/inherit from standard dc motors ? take it further, relating to a standard kv-rating, or torque values..or something..? any idea why rollout 1:1 is what stock trucks have?

thanks for the pinon link, i would really like to not buy pinions there. i bought a few once, only to get the messages they're sold out, and whether i would like this and that instead. seeing how the MM XL is 'for sale' there and not in stock, instock and out of stock has its own meaning there.

the battery question was merely a theoretical question on the views of cell counts. I dont have any fancy idea of 8s on and e-savage dont even have an 8s esc to whip But I do have an idea of an alza racing savage flux chassis with 4 x 2s and a leopard/toppower motor. (8s wont fit inside)

heres a funny pic (ooh, that why iphone charge so slow!)


I had a bad cell on 3s pack once, i can imagine a bad cell in an 8s pack would be terrifying annoying. where the 4 x 2s would leave 3 x 2s, thats the more 'practical' ideas i was thinking of. (like 2 x 2s could be used in 4 rc's, and fewer cells stacked in a pack) and maybe in an 8s pack, the 6 inner cells, those would be sitting like a can of fish heating up etc.. As i mention the lipo serial wiring was another matter itself (resistance and neatness). still, i dont see why some 10awg wiring resistance (multi-strand and all) would matter THAT much. it would also give some means of relocating 'weight'/CofG on a truck. like to adjust for wheelies and no-wheelies.