Felony Back to back speed runs ... Mmx8s 1717 1650kv... what sort of gearing?

Sir Marz

Member
Messages
31
Reaction score
12
Hey guys so I'm building a felony that I'm hoping to have some reliable speed with back to back speed runs

What sort of gearing is ideal for the Mmx8s 1717 1650kv. Stock wheels and diffs .

I'm not looking to break any records obviously but just have some fun going fast .

Stock motor is relatively smaller ... so does that mean the same load the motor is moving is relatively easier to move along side the lower kv motor.
 

real_name_hidden

Bash/Break/Fix/REPEAT 🤣
Premium Member
ArrmaForum Fan
Hospitality Award
Build Thread Contributor
Messages
3,604
Reaction score
6,780
Location
Missouri/Illinois
Arrma RC's
  1. Limitless
  2. Kraton 6s
From your post it seems very vague…
What cell? 6 or 8?
But speedrunning draws a lot of amp. So back to back on extreme gearing you’re not going to be able to go back to back. It will get too hot
 

Fishtank

work the hardest when no one is watching
Premium Member
ArrmaForum Fan
Build Thread Contributor
Messages
849
Reaction score
2,219
Location
Arizona
Arrma RC's
  1. Infraction
  2. Kraton EXB
I'm running a 23t in one and and a 25t in the other. 46t center diff with 500k. Both infractions.
EECFBED3-6BC3-42CE-9BD3-5EAC25434A22.jpeg
 

Sir Marz

Member
Messages
31
Reaction score
12
I'm running a 23t in one and and a 25t in the other. 46t center diff with 500k. Both infractions. View attachment 258823
What sort of speeds are you getting and how are the Temps bashing if you do that ?
From your post it seems very vague…
What cell? 6 or 8?
But speedrunning draws a lot of amp. So back to back on extreme gearing you’re not going to be able to go back to back. It will get too hot
8s

I get that it will get hot altho ...
The stock system does relatively ok with a 16t

Castle 1717 1650kv is bigger with a slightly lower kv and the Mmx8s is a better esc than stock .
So how much more can it handle consistently.
 

Diem Turner

Yes...I have a Premium Member
Premium Member
Rig of the Month Winner
Build Thread Contributor
Messages
5,419
Reaction score
13,638
Location
Wienerslider, Germany
Arrma RC's
  1. Infraction
  2. Kraton EXB
FWIW, speed running and "back to back" are contradictions in terms in my view. What you're talking about is high speed bashing. Sorry if I'm being a bit pedantic about this, but I think we should be clear with our terms so as to avoid confusion.

With 25/46T gearing you're not going to be able to bash around for more than a few minutes before reaching thermal limits. Temperatures will be dependent on a number of factors, the primary ones being ambient temperature and what your cooling setup looks like. Other factors like parasitic drag, driveline binding, drive shaft oscillations and several others will also come into play so this will make it difficult to transplant one user's experience to another car under different conditions.

All that being said, I'd start from a 20T pinion and monitor your temps and then gear up or down from there. It's will also depend on your driving style of course, so that's another factor that's difficult to account for. Best practice for speed bashing would be to get two really powerful 12V 40x40x28mm fans and run them off a 3S lipo.
 

Fishtank

work the hardest when no one is watching
Premium Member
ArrmaForum Fan
Build Thread Contributor
Messages
849
Reaction score
2,219
Location
Arizona
Arrma RC's
  1. Infraction
  2. Kraton EXB
FWIW, speed running and "back to back" are contradictions in terms in my view. What you're talking about is high speed bashing. Sorry if I'm being a bit pedantic about this, but I think we should be clear with our terms so as to avoid confusion.

With 25/46T gearing you're not going to be able to bash around for more than a few minutes before reaching thermal limits. Temperatures will be dependent on a number of factors, the primary ones being ambient temperature and what your cooling setup looks like. Other factors like parasitic drag, driveline binding, drive shaft oscillations and several others will also come into play so this will make it difficult to transplant one user's experience to another car under different conditions.

All that being said, I'd start from a 20T pinion and monitor your temps and then gear up or down from there. It's will also depend on your driving style of course, so that's another factor that's difficult to account for. Best practice for speed bashing would be to get two really powerful 12V 40x40x28mm fans and run them off a 3S lipo.
I'm an old dirt basher that has taken to the road in the last year so I am still learning myself. but I do have a lot of time on task.
I can only speak for myself but I'm running 23T and 25T (sometimes 26t) with a 50t center diff. I run 60k,500k,30K diff fluids with a max6/1650Kv I run fans on motor/ESC. My temps run 110f-130’s. I’ve run both cars into the low 90’s but most of my driving is parking lot, street driving so 60’s-80’s MPH mostly. I’m not looking to set speed records just having fun. I run one car on 8S the other on 6S. I would definitely listen to @Diem Turner he’s WAY more “street” wise then I. I feel like I’m painting by number when I look at his rides!😂😂😂😂
DEFDB961-7609-46F8-9DA3-D2CB30666997.png
6E76A16D-CF5E-45D3-846E-9945334D07AB.png
B0B32FA0-1BC1-4A02-B832-B49AE5138009.png
F6D373C0-51D2-4C7F-BE15-39F5B1767422.png
 

dk10438

Well-Known Member
Messages
513
Reaction score
671
Arrma RC's
  1. Limitless
Hey guys so I'm building a felony that I'm hoping to have some reliable speed with back to back speed runs

What sort of gearing is ideal for the Mmx8s 1717 1650kv. Stock wheels and diffs .

I'm not looking to break any records obviously but just have some fun going fast .

Stock motor is relatively smaller ... so does that mean the same load the motor is moving is relatively easier to move along side the lower kv motor.
as previously noted you need to be more specific with your goal and setup. However, on a V1 Limitless 34T spool/35T pinion I'm getting 110 MPH on 6S MMX8S/1717-1650
 

Sir Marz

Member
Messages
31
Reaction score
12
T
FWIW, speed running and "back to back" are contradictions in terms in my view. What you're talking about is high speed bashing. Sorry if I'm being a bit pedantic about this, but I think we should be clear with our terms so as to avoid confusion.

With 25/46T gearing you're not going to be able to bash around for more than a few minutes before reaching thermal limits. Temperatures will be dependent on a number of factors, the primary ones being ambient temperature and what your cooling setup looks like. Other factors like parasitic drag, driveline binding, drive shaft oscillations and several others will also come into play so this will make it difficult to transplant one user's experience to another car under different conditions.

All that being said, I'd start from a 20T pinion and monitor your temps and then gear up or down from there. It's will also depend on your driving style of course, so that's another factor that's difficult to account for. Best practice for speed bashing would be to get two really powerful 12V 40x40x28mm fans and run them off a 3S lipo.
Thank you kindly for all the information presented... speed bashing would be a better term yes ... I understand what your saying about all the contributing factors with regards temps .

A solid base line is a stock felony .

poop fan on the esc and motor.

But you can get through a pack of 5000mah batteries without reaching thermal cut off on a 16t .

If it reached thermal that quick they wouldn't sell it as an rtr with that setup .

So I get your 20t gearing as that is basically stock gearing ... but then I might aswell just get better cooling for the stock set up .

Is there like some sort of threshold of temp and speed

The 1717 is equivalent to the 49 series which is what's in the kraton 8s, bigger in all directions.

That extra size should accommodate for something.theres no replacement for displacement ...At the end of the day it's just what's on paper .... taking out all the unnecessary factors ....

Realistically what should the 1717 be capable of with 2× 40mm fans at 21k rpm .

If the 2050 spectrum is good at 16t

"On paper"
 
Top