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What Chassis? 1:27 On Road

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What Chassis? 1:27 On Road

Old 02-03-2019, 03:29 PM
  #31  
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You are a couple of years away from having true tunability in a 130 sized brushless motor. There isn't enough market yet to support the development that we see in the 540 sized VE motors. If you want to pay 540 prices for a 130 motor then you may be able to speed development. I have seen turn ratings on the 380 size range as well as some of the 540's. Example: Traxxas Velenion 380 is rated at 4000KV and 8T. Granted it is not a sensored motor but it suggests that the math is available for an equivalency formula. It would be a whole lot simpler to just group by voltage and leave it at that. Box stock, improved stock including LM at 4.8 and 7.4 modified.

EMU, talk to Tommy. He and I did the testing in prep for a Carolina Cup event.

I don't have nor do I want a dog in this fight but I refuse to watch the 4.8V cars(brushed or VE) pushed out by their higher voltage cousins.
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Old 02-03-2019, 03:33 PM
  #32  
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Originally Posted by EMU
A brushed motor to be used vs LiPo 3500kv, my best choice for a small track would be PN 43t or PN 39t. These will be able to get great torque off
While you may wish that the brushed motors are rated in KV, I wish that the brushless motors were rated in turns. With options to replace rotors, and different variables that come into play with designing a motor for a certain KV... it creates a difficult understanding of what the motors true rating is. A "3500kv" motor with a larger or smaller rotor will have a different true KV rating, as the change in magnetic field will change the RPM/V. In order to have uniformity among the motors, turn ratings are more accurate, and then you can tune with rotors. Some motors might have more winds, but a weaker magnet and make 3500kv, others may have fewer winds and a very strong magnet and make the same KV, but loads more torque. Swap out the rotor for the same weaker one from the first motor, and you could get 1000kv more (theoretical explaination).

Brushless motors are very linear with their voltage scaling, brushed motors are not. This creates an issue when trying to give a brushed motor a KV rating.
I always hear this from guys that are racers first and foremost, while airplane and helicopter guys prefer the kv rating. Thanks for the Info though, very helpful as always!
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Old 02-03-2019, 04:23 PM
  #33  
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Fliers are somewhat limited in prop options, while racers have more gearing options and torque is usually more indicative of speed on small to medium sized layouts which use slower corners. High speed, flowing layouts are more rpm reliant.

in my real world testing, I find that the 2S 3500kv has very similar feel to a 39t motor, but with the lower mass of the GLR chassis, it comes off the corner like a rocket.

I tend to prefer the higher turn modified motors to the lower turn ones. Earlier application of torque, with a little less on top. It also allows use of larger pinions, which wear slower and provide better mesh. More motor rpm=heat, and I like to use as much motor is required to do the job, I find that this approach yields more consistent lap times, and better runtime. Motoring up too much is often not the best solution. More motor = more problems...
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Old 02-03-2019, 05:01 PM
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$50 WLTOYS might surprise your mini-z's
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Old 02-03-2019, 05:06 PM
  #35  
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Originally Posted by EMU
Fliers are somewhat limited in prop options...
you might think that but the truth is there are so many variables, section profiles, tip shape, blade shape. it all has effects. That said I think surface vehicle competition does have more variables. I am fairly new to racing, most of my car experience is just bashing around the yard with my son and our Emaxx's.
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Old 02-03-2019, 06:12 PM
  #36  
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Originally Posted by Buzzsaw46
you might think that but the truth is there are so many variables, section profiles, tip shape, blade shape. it all has effects. That said I think surface vehicle competition does have more variables. I am fairly new to racing, most of my car experience is just bashing around the yard with my son and our Emaxx's.
I meant that on road RC, generally we use a wider range of the RPM in the motor, and earlier peak torque usually benefits more than a flatter torque curve. Where in flying, the peak torque is wanted higher in the rpm range as there is more resistance on the prop as the rpm increases. High early torque is less relevant flying because there is not a direct transfer of torque to speed.

I like motors with more low end grunt because I want the maximum acceleration off of the slowest corners. Ones that I am already taking at a moderate speed, don't need quite as much power to come off of.
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Old 02-04-2019, 02:32 AM
  #37  
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Originally Posted by EMU
I meant that on road RC, generally we use a wider range of the RPM in the motor, and earlier peak torque usually benefits more than a flatter torque curve. Where in flying, the peak torque is wanted higher in the rpm range as there is more resistance on the prop as the rpm increases. High early torque is less relevant flying because there is not a direct transfer of torque to speed.

I like motors with more low end grunt because I want the maximum acceleration off of the slowest corners. Ones that I am already taking at a moderate speed, don't need quite as much power to come off of.
Makes perfect sense, in helis you really only use 20% at the top of the power band. It seems I have much to learn about race motor dynamics, having never been limited by voltage constraints low end torque has never been an issue with our yard machines. With only 4 AAA cells allowed in most classes. low end grunt becomes a serious consideration.
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Old 02-04-2019, 06:34 AM
  #38  
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Oh this is not going to fun. I can’t even describe just how small some screws are.
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Old 02-04-2019, 06:46 AM
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This is a great exercise to show the importance of high quality tools as opposed to the Harbor Freight bargain bin items a lot of people use.
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Old 02-04-2019, 06:47 AM
  #40  
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Originally Posted by Billy Kelly
Oh this is not going to fun. I canít even describe just how small some screws are.
Yes 00 phillips is very small. One thing thats helped me with assembly is using a paper plate or something to hold all the hardware to keep it somewhat organized and from being lost on the floor.
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Old 02-04-2019, 06:55 AM
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Originally Posted by magnum_junior
Yes 00 phillips is very small. One thing thats helped me with assembly is using a paper plate or something to hold all the hardware to keep it somewhat organized and from being lost on the floor.
like the plate idea. Used to do that. I’ve got a heavy paper towel under to catch things. Worst thing I see going forward is there’s no listing for what bags parts are in for each step. Unfortunately I don’t have a space to just open up bags and sort things out. Plus it’s online only for guide. For me that’s an automatic F grade. At least the Serpent kit I built with online guide listed what bag to use for steps.

only some Phillips screws. Most are hex. Having to use the Allen wrenchs included in kit. Don’t own any this small
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Old 02-04-2019, 07:15 AM
  #42  
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Originally Posted by Billy Kelly

Oh this is not going to fun. I canít even describe just how small some screws are.
Billy,
Looking good. These little cars do mean little screws.....I had bought a pair of 3X readers (usually wear 1.25X) to work on some small helo's awhile back but I am serious about looking for a pair of 5X readers. This whole getting old stuff is for the birds.

Getting back to the discussion about motor. I have been flying e-powered planes for 25+ years and I was an early adopter of BL power. Just about the time I was getting pretty darn good at hucking a plane around the sky out-runner motors started to become more mainstream. The packaging was great and these motors where a heck of a lot less expensive the the US and European made in-runner bit for me they did not cut it. I had gotten use to using in-runners in gear boxes and liked the efficiency and power handeling of a high KV motors but would gear them really short to keep the amps down and flight time up. The great thing about using a gearbox was that you could switch up the gearing to match what you were trying to achieve......I went through a lot of Green Loktite back in the day. My experience with competitive RC cars is much more limited and having raced an old TA03 a bit back in the mid '90's...I did not formally race all that long just because of the commitment you had to make to be competitive, that was also right around the time I got a bit tired racing boats and spent three years campaigning a MKI Toyota MR2 in SCCA C-Stock so both time and funds were hard to come buy. With that said after getting back into RC wheels vehicles a couple years ago the technology that is put into the brushless ESC's these days is pretty impressive, you can play with a lot of parameters for sure and they can significantly change how the car reacts. It is funny reading about these motors, I keep forgetting just how small they are. I use to run these US built in-runners in my sub 20oz planes which at the time were pretty darn small, the other day I got to thinking if they would be usable in this scale of car because the KV's are pretty close. The I realized that the motors I was thinking about are 20MM in diameter.....These cars are pretty darn small.

Cheers,
Jim
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Old 02-04-2019, 04:51 PM
  #43  
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Jim, our back ground in e-power is very similar. I have a few 20mm Hackers, 28mm Mega, and Aveox. I had the same issue with outrunners I was used to high kv inrunners in a gearbox
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Old 02-04-2019, 05:35 PM
  #44  
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Originally Posted by Billy Kelly

Oh this is not going to fun. I canít even describe just how small some screws are.
Looks awesome! Keep going, I bought a lighted magnifying glass for working on tiny models.
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Old 02-04-2019, 07:46 PM
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Looks awesome! Keep going, I bought a lighted magnifying glass for working on tiny models.
When I built my Atomic AMZ most of the build was done under my lighted magnifying glass. To be honest it was a fun build, but it was really nice going back to a 1/10th scale build afterwards!
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