did i go the wrong way?

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ksrichard

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lemoyne pa
RC Driving Style
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Ok now I'm really confused so ill ask u. Whats better for speed runs a vxl 3500kv or viper vx4r.45 4500kv. For speed runs. Vxl on 3s w 31/76, viper 25/76? I only do 1-2 hard runs and let it cool. Overheating not an issue. I never drain a full charge and motors never to hot to touch. I want faster.. Right now I'm hitn 55 on both. That seems like a $200 mistake
Please help.
 
Mathematically here's what you do. I'm on my phone so you will have to do it. If you're running 3 cells do the kv x voltage so on 3 cells for the vxl its 12.6 x 3500. That gives you your motor rpm and it works for every kV rating. Next is your gear ratio. Take the spur gear teeth and divide it by the pinion gear teeth. Thecloser to 1 you get is your faster ratio so as you can see you COULD in theory get the lower kV rating to turn faster. The lower kV rating is your best bet to get as close to a 1 to 1 ratio as possible because it makes more torque. Hope that helps
 
One quick maintinance thing, you said you never drain a full charge, do you discharge your lipo's before balancing and charging them?
 
No. Uh ohh!! I thought if i balanced them on every charge thats ok.

---------- Post added at 5:28 PM ---------- Previous post was at 5:16 PM ----------

So my trusted lhs just made a sale?. They said the viper combo would hit 80-100mph . Have i been
Hosed..? Hope not I've spent b.out 6g last year. So a highr Kv is more likely to overheat?
 
I always discharged every 3-4 uses.
 
No. Uh ohh!! I thought if i balanced them on every charge thats ok.

---------- Post added at 5:28 PM ---------- Previous post was at 5:16 PM ----------

So my trusted lhs just made a sale?. They said the viper combo would hit 80-100mph . Have i been
Hosed..? Hope not I've spent b.out 6g last year. So a highr Kv is more likely to overheat?

A higher kV will turn more rpms. As I said the rpm is kV x volts. On the same vehicle with the same gearing the higher kV motor will make it faster but if your gearing is too high it will overheat.

The higher the kV the lighter the vehicle should be. 1/8th scale is typically 2200kv or less SCT about 3500 to 7000 and then smaller scale can go higher. The lower the kV the less rpm but more torque
 
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+1. I run a 6800kV motor on a 1/18th scale truck and a 10,250 kV on a 1/24 scale. Lower kV means more torque. When all is said and done, My Revo 3.3 conversion will be running a 2650 kV motor.
 
How do i discharge a lipo battery?
Ok. Confused again... 3 cells is 11.1v where does the 12.6 come from?
Thanks for your help.....
So lhs didnt play me. I need to change gearing. Any ideas. Up pinion or lower spur?.
 
To discharge lipo, there should be a setting in your charger for it.
 
How do i discharge a lipo battery?
Ok. Confused again... 3 cells is 11.1v where does the 12.6 come from?
Thanks for your help.....
So lhs didnt play me. I need to change gearing. Any ideas. Up pinion or lower spur?.

If you have a charger that can discharge it is one way running it in a vehicle is another. 12.6 is what a 3 cell 11.1 v charges to.

I'm not sure if it matters to go up on pinion or down on spur but getting closer to 1:1 is going to make it faster. The result in dividing the spur gear teeth by the pinion gear teeth is how many times the pinion turns to make the spur turn one time. My emaxx is running 34/47 so the pinion turns 1.38 times to make the spur turn once. If you could gear 1 to 1 whatever the motor rpm is would be the transmission rpm also. So if you could gear the pinion at 30 and the spur at 15 the motor rpm would be say 60000 but the transmission would be 120000. I'm only throwing that out there as an example. To do that without burning up the motor or ESC you would probably have to have an 1/8 scale motor on a 1/16 vehicle.
 
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12.6V is what a fully charged 3S lipo will be. 4.2V per cell times 3 is 12.6 or (4.2 X 3 = 12.6). I usually use the nominal voltages for these kinds of calculations because it will give you more of an average (although you can calculate it either way as long as you use the same for all calculations). Nominal being the 3.7V per cell or the 11.1V that you're used to seeing.

So the 3S 3500kv will give you on average about 38,850 RPM (11.1 X 3800 = 38,850)
The 2S 4500kv will give you on average about 33,330 RPM. I'm assuming that you're running the 4500kv on 2S because that is the maximum recommend voltage for that motor per the Users Manual. If you are running it on 3S then you could very likely damage the motor or the ESC eventually.

31/76 gearing will give you a pinion/spur gear ratio of roughly 2.45 (76/31=2.45)
25/76 will give you roughly 3.04
As BG said above the lower your ratio the faster the kit will be. However it also requires more power to turn it as well. This either means more torque is required or it means it will generate more heat. As I pointed out in another post a 4500kv running roughly that same gearing would not get you more than 55-65MPH. i dont care what you LHS or what Traxxas box says. I've been there done that with multiple different motors. Yes if you over gear the piss out of the VXL on 3S with street tires that ballon alot, like Anacondas, you can make the Rusty go somewhere in the 60-68MPH range but you run the risk of blowing out your tires from balloning and you'll heat up that VXL motor very, very fast. The balloning basically increases whats called your "rollout" which also affects your possible top speed. If you're gonna do speed runs with 1/10 scale electronics and you wanna get over the 60+MPH mark without worrying about blowing out your tires while increasing the rollout but not really increasing rotational mass then look at the Jaco foams for the Rustler. There are other things that can come into play like transmission/diff gearing which affect whats called your "overall gear ratio" but I've probably already given you more than enough to process and most of the time transmission/diff gearing isnt soemthing you can change a whole lot anyway.

Now the VXL 3500 is only a 2 pole motor and 4Poles with the same KV rating are gonna give you more torque with the same RPMs. More toque is better for turning those lower gear ratios. However, the higher the KV rated motors will have more RPM per volt but if you have to drop a cell to use it then the advantage is lost and the higher the KV the lower the amount of torque it typically has. Additionally a 550 can will give you more torque than a 540 can so generally speaking your best bet would be a 550 can 4 pole motor thats like double win in the torque department. So when doing speed runs, it becomes this game of finding which motor have the best balance between RPM and torque. Also remember that high KV doesn't mean crap as long as the are sufficient ways of lowering your spur/pinion gear ratio. Most of the time if proper gearing options are available the higher cell count + gearing will usually defeat higher KV. Another way to think of it in terms of doing speed runs would be to find the motor that has the highest KV that will still run on the biggest lipo cell count you want to use and then try and find a 4pole 550 can version of it. For 1/10 scale thats usually gonna be 3S. Although there are a couple out there that will run on 4S. The Castle 2400kv and (supposedly, never tried it) the Tenshock sc401 4000kv. (Btw, as a side note if you go looking for Tenshock motors the 4000kv I mentioned was the older Version1 line. The newer Version 2 line claim to have a 4400kv that will handle up to 4S and a 5000kv that will handle 3S. The Amp draws on these motors are very high for 1/10 scale motors though. anywhere from 180-200A peaks.)

So in this example not only is the 3500 able to push a higher gear ratio its also pushing more RPMs = win. Now I get the impression since both motors are hitting about the same speeds you are running the Viper motor on 3S and basically whats happening is your extra KV is being nullified by the VXLs lower gear ratio. This is why, if memory serves, when you brought a semi related topic up before when you were having problems with your VXL ESC I suggested you get a Castle 1410 3800kv 4 pole or a Tenshock SC401 4000kv 4 pole. Both of these motors have higher KV ratings that the VXL, they are both 4pole and they are both 3S compatible (The Tenshock is also a 550 can motor). Actually according to specs I've seen online at multiple places the SC401 4000kv is supposed to be able to handle up to 18V which means you could theoretically run it on 4S. In order to do that though id say youd want 120A minimum ESC and probably 50+C rated lipos. These are the two best motors I've seen for doing speed runs. I have quite a bit of experience doing speed runs with Rustys using both with 1/10 scale electronics and 1/8 scale.

You should watch my Electric 101 Video series thats stickied in these forums HERE. It goes over everything thats been said here and much more.
 
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I have a castle 4600kv motor I'm trying to sell. Its brand new never run. It should work great with that vxl ESC. It will have torque and rpm on 3s which is what you're looking for. If I'm not mistaken there is no motor limit on the vxl and it has a high amp rating
 
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I would not run a Castle 1406 on 3S with the VXL ESC. The VXL ESC has similar specs as the Castle sidewinder and Castle advises against running anything higher than their 3800 on 3S with a sidewinder. :2cents:
 
If that's true then i take back what I said. But castle makes junk escs...lol the reason the motor is for sale is the mamba max pro I got with that motor in a castle combo was bad from the factory, didn't even run for a second. That's ESC number 3 replaced by castle
 
This is hard. I know the vx4r.45 is for 4x4 apps. I thought it could be used on 3s speed runs. Top speed
And done.thanks again. I love rc everything. a lot to learn about brushless motors/esc.
 
If that's true then i take back what I said. But castle makes junk escs...lol the reason the motor is for sale is the mamba max pro I got with that motor in a castle combo was bad from the factory, didn't even run for a second. That's ESC number 3 replaced by castle
I heard some complaints in the RC community a year or 2 ago about some quality control issues they were having but I havent heard anything in the last year or so. I have 2 MMMs, a sidewinder V2, Sidewinder V3, and an MMP an dall of them are still working although one of my MMM hasnt been used but once but the rest are all going strong.

I will say that I did read a would-be test of some common ESCs on another RC site that did rank the VXL ESC above Castles Sidewinder but not by much. Overall it ranked poorly for 3S usage. I say "would-be" because the manner in which they were tested in lacked a control for one and the testing methods had variables in it but i think overall it was sufficient to paint a rough comparison between the different models used.
 
This is hard. I know the vx4r.45 is for 4x4 apps. I thought it could be used on 3s speed runs. Top speed
And done.thanks again. I love rc everything. a lot to learn about brushless motors/esc.
The motor looks like a fine SCT 4X4 motor for 2S use which is what most SCT run on, at least the ones racing. Not so good for speed runs I'm afraid :(
 
I'm bummed.. I trusted my lhs. I spent a ton of money there. Why would they sell me something that wont fit my needs? They told me to gear up 2 teeth. I contacted viper I'm waiting for a return message. Thanks rc friends..
 
I heard some complaints in the RC community a year or 2 ago about some quality control issues they were having but I havent heard anything in the last year or so. I have 2 MMMs, a sidewinder V2, Sidewinder V3, and an MMP an dall of them are still working although one of my MMM hasnt been used but once but the rest are all going strong.

I will say that I did read a would-be test of some common ESCs on another RC site that did rank the VXL ESC above Castles Sidewinder but not by much. Overall it ranked poorly for 3S usage. I say "would-be" because the manner in which they were tested in lacked a control for one and the testing methods had variables in it but i think overall it was sufficient to paint a rough comparison between the different models used.
All 3 castle escs I've had have all gone back to castle and replaced under warranty. First was a mm that went up in flames, second a mm that let the smoke out and now a mamba max pro that was gone right out of the box. I wrote a little note on my return paperwork about how I try to be a returning castle customer but its getting harder to do. Spend 200 dollars on their product take the time to install on the truck which on a savage xs the motor location is not easy to change it out find out its DOA and have to take the time to remove it again. Now I've paid to ship it back...not a good experience
 
All 3 castle escs I've had have all gone back to castle and replaced under warranty. First was a mm that went up in flames, second a mm that let the smoke out and now a mamba max pro that was gone right out of the box. I wrote a little note on my return paperwork about how I try to be a returning castle customer but its getting harder to do. Spend 200 dollars on their product take the time to install on the truck which on a savage xs the motor location is not easy to change it out find out its DOA and have to take the time to remove it again. Now I've paid to ship it back...not a good experience

Yeah that sucks man. I've become more of a Tekin guy over the last 1.5 years or so but I've had pretty decent luck with the Caastle stuff i have bought. *crosses fingers*
 
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