Speed Calculator

[skellyo]

Just out of curiousity Brian, why do you have the B4/T4 transmission ratio under the differential gear ratio and not under the transmission gear ratio section?

[BrianG]

I don't know. A mistake perhaps?

FYI: I took a look at adding a popup table to list speeds with different pinons, or spurs, whatever, and decided against it. Just adds a level of complexity I don't really want to deal with. More like tedium than complexity.

What I DO want to add is an alert of some kind which will tell the user if they are geared too high. There is a point in gearing where the motor is not spinning fast enough per mph for smooth low speed/take-off operation (around 1mph). Looking back, it seems I set my vehicles up for around 1000+ rpm per mph and everything runs fine. I'd like to know if there is a good rule of thumb regarding this, but would also depend on motor size of course.

On a similar vein, GriffinRU had provided some input on this topic a while back with regards to the minimum motor rpm needed for adequate back-EMF pulses from the motor. The idea was dropped because my simple mind could not grasp what he was talking about, but I think it would be worthwhile to have this kind of data available.

[BrianG]

I posted the following in another thread. If it IS accurate, and would be of use, I can add it to the calc:

Originally Posted by Me

BTW: I don't think speed scales like the size does. From what I gather from this page, the formula for finding scale speed is:

1:1 speed = SQRT(scale) X scale_model_speed

So, if your 8th scale RC does 60mph, that scales up to SQRT(8) X 60 = 169.2mph.
Similarly, if your 10th scale RC does 90mph, that scales up to 284mph.

If someone can verify this, I can add this to the speed calc.

Just want to make sure the formula is accurate...

While I'm at it, no one has any information about the following?

Originally Posted by Me again

What I DO want to add is an alert of some kind which will tell the user if they are geared too high. There is a point in gearing where the motor is not spinning fast enough per mph for smooth low speed/take-off operation (around 1mph). Looking back, it seems I set my vehicles up for around 1000+ rpm per mph and everything runs fine. I'd like to know if there is a good rule of thumb regarding this, but would also depend on motor size of course.

On a similar vein, GriffinRU had provided some input on this topic a while back with regards to the minimum motor rpm needed for adequate back-EMF pulses from the motor. The idea was dropped because my simple mind could not grasp what he was talking about, but I think it would be worthwhile to have this kind of data available.

[portyansky]

Is there any way you could put info on 4wd elec trucks (zx-5,xxx4 etc...)
Thanks, I love this program!

[BrianG]

Well, I would need the info you want entered. Read this (specifically the topic "How do I submit data for a transmission or differential?"). I hate dissecting parts lists and exploded diagrams for the needed values, so if you can provide the data, I will be more than happy to add it...

[RC-Monster Mike]

http://rcgearing.com/

Here is another potentialy helpful gearing site. :)

[SnoopMaxx]

Hi Brian
I really love your calculator

My E-Maxx has a top speed around 28 Mph with 2 Kyosho 550 motors
(Same as a 1750kv rating)

Would a MMM v3 2200kv be too much for my old Maxx ? (35 Mph)

[brushlessboy16]

Originally Posted by SnoopMaxx

Hi Brian
I really love your calculator

My E-Maxx has a top speed around 28 Mph with 2 Kyosho 550 motors
(Same as a 1750kv rating)

Would a MMM v3 2200kv be too much for my old Maxx ? (35 Mph)

depends on what batts you run, and what you have done to the drive train..

[SnoopMaxx]

3906 with 2.5r drive shafts all around ... snaps like twigs

2 x 6cell 4000mah batt´s
Need 3.3 drive shaft and diff ... would that be enough ?

[brushlessboy16]

i dont think the 2.5's or the 3.3's will be enough.. you might need somehybrid diffs for 6s, and definatley get steel idlers for the trans

[SnoopMaxx]

How ´bout on 4s ? or is that to low volt ?
I only have two 6cell NiMh batt´s at the moment

I´d like to get a few set of A123 cell´s
I heard they were safer compared to some LiPo´s

[brushlessboy16]

Originally Posted by SnoopMaxx

How ´bout on 4s ? or is that to low volt ?
I only have two 6cell NiMh batt´s at the moment

I´d like to get a few set of A123 cell´s
I heard they were safer compared to some LiPo´s

4s you would still need a driveline update, A123 are technically safer then lipos, but as long as you have some common sense lipo's should be fine.

[SnoopMaxx]

Thank´s

[Jabe]

How about, in "motor selector" there is vehicle weight, but is it lbs or kg or something else??

[brushlessboy16]

If your willing to add Then cen matrix Tr, the diff ratio is 2.8888888 9/26.

Spur gear is 66t stock.