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jdh6fan

New guy here looking for advice

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Hi my name is Jeff.  I recently decided I wanted to build an RC car to play around the yard with.  I have a slash that I have had for years but was looking for something different.  I ended up buying a TRF201 of the Tamiya site because it looked like a fun build and I felt the price was right.  My questions are what kind of electronics would you use just to play around with.  Nothing real expensive but not junk either.  I have read on here that there might be some clearance issues with the esc with the body the car comes with, so Im guessing that using an esc with a fan is out.  What is a good servo for a buggy.  I seem them priced anywhere from less than five bucks plum up to more than I have given for real cars.  Just looking for your opinions on this stuff.  Thanks for your time.

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If you are building it purely for fun with no racing aspirations, a cheap brushless combo from Hobbyking ought to be fine, along with one of their budget metal geared servos.

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You're lucky because RC electronics are now cheap and have many, many options to choose from. You can buy an brushed ESC/motor combo for as low as $25 and brushless combo for as low as $50. I would recommend the Hobbywing (as mentioned by TurnipJF) Quicrun series (brushed and brushless). They are waterproof so getting them wet is no problem. With regards to servo, I would recommend PowerHD or JX servos. They are cheap, reliable and many are also available in waterproof. Get at least a digital servo with metal gears, bearings and speed of at least 0.11secs (or faster).

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Welcome.

TRF201 is a good choice. $175 is a steal.  For ESC, a lot depends on what kind of a motor you want to run. 

[1] If you want to run brushed motors, Hobbywing Quicrun 1060 can run any motor down to 12turn.  About $20 for this ESC.  Tamiya Sport Tuned is usually the first step in motor upgrade, and it's about $17.    

[2] If you want to run brushless, there are cheap sensorless combos.  They are simple, rugged, waterproof, but ESCs often have fans.  They sell all kinds of combos.  As for ESC, don't go for anything less than 60A ESC.  And 60A can handle about 3000kv.  So a "healthy combo" would have 60A ESC, and around 3000KV motor.  (They even sell 45A ESC with 5000KV 3660-size motor, but the ESC could burn out in a second)  60A with 4000kv would be pushing it.  It all depends on how you drive and the temperature.  If you are driving in arctic circle, you may be fine to us 60A with 5000kv.  If you slowly raise the RPM, 3500kv would be fine in hot summers too.  You can experiment.  I have a 60A 3300kv combo.  It's fine, I don't drive in hottest days anyway.  These combos can be found for about $45.  

The most common size is "3650."  36mm x 50mm.  3660 is a much bigger motor, you need bigger ESC, and you may need different pinions too.  Don't get motors with fins either.  Fins take up the space, so those are actually smaller motors. (That's fine for light on-road cars, but for buggies, you'd want some torque)  These come with connectors soldered on.   

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[3] If you want to bash with controlled driving style (meaning without amazing power), you might go with Tamiya TBLE02S.  It's a moderate ESC.  It has no fan.  It's also a 60A ESC.  It cannot handle anything faster than 13.5t (about 3000kv).  It would be a good starting point.  But many Sensored motors don't come soldered.  If you don't have it already, you might have to spend $15, and get yourself 60w soldering iron.  Anything less (like 45w iron I had before), would make you doubt your soldering skills.  A lot of people use TBLE02S + 13.5t.  Simply because TBLE02S is supplied with kits and 13.5t is fast enough for bashing.   TBLE02S can be found for about $25, 13.5t motors are about $45.   

[4] Or you can get Hobbywing Quickrun 10BL120 ESC.  TBLE02S has no fan.  So maybe 10BL120 could run 11.5t without a fan too. (I have no idea if that's possible)  With the fan attached, you could run 8.5t which would give you 5000kv = 37000 RPM at 7.4v.  That's too fast for small spaces around my place.  But if you want to set a speed record in an empty runway or something, that's possible with 10BL120.  Even if you have 120A ESC, I still think 13.5t motor would be a good starting point.  You can get faster ones as you get used to it.  Amazon sells 10BL120 for $42.  Sensored brushless motors start from $45.  

[5]  There are literally hundreds of servos.  Metal gears is good.  You really don't need to spend more than $20.  Even $3 Hobbyking servos are faster and stronger than Futaba S3003 servo that used to be the industry standard for 20 years.  

[6]  For radio, I replaced 2 dozen old Futabas with Flysky GT3B (GT3C is better).  For my bashing needs, it's fine.  If you want more function, you could get a Radiolink RC6GS.  It comes with a gyro receiver (though, if you are just bashing, spinning out of control is part of the fun--you can freely adjust the degree of gyro).  If you are race-oriented, Futaba 3PV is basic in its functions, but it should give you the fastest response time.   

 

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Hey, I really appreciate the info.  If I'm understanding all this right for my basic playing around one of the lets say second or third tier brands would be great for my needs.  This is good news, I guess I can always buy better and more suited items as time goes on and I learn more.  I'm really thinking brushless because my slash is brushed and Im just looking at doing something new.  I find that it runs great with a 6 cell pack and if I want to go a little faster I just use a 7 cell pack.  Bad news is all my packs have went bad since they have just been setting for 3 to 4 years.  Ive tried charging and discharging them but I don't think they are coming back.  This might be a good chance to get a lipo charger and try some 2s packs.  I was looking at the Flysky gt3 due to the receivers being somewhat inexpensive and what looks to be available fairly easily.  Also I might have already bought and snuck in a new Sand Scorcher that will also need a radio and receiver and thought the GT3 might be nice for it too.  Also could you direct me to some sort of easy to use chart to figure gearing.  The TRF doesn't come with a gear for the motor so I need to do some research and figure that out.   Anyways thanks for taking the time to answer some of my questions.  

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You might also want to check out Radiolink RC4GS TX/RX. I chose this over FlySky. Works great, feels great and very nice features for its price. The RX even came with a Gyro.

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7 hours ago, jdh6fan said:

Also could you direct me to some sort of easy to use chart to figure gearing.  The TRF doesn't come with a gear for the motor so I need to do some research and figure that out. 

This final drive ratio (FDR) chart from a Hobbywing 3650 motor datasheet should be a good starting point. An FDR of 7.0:1 means that 7 rotations of the motor results in 1 rotation of the wheels.
YWChC7C.png

The formula to calculate FDR for a TRF201 is:
FDR = (spur_teeth/pinion_teeth)*2.6

So for example a 25t pinion and the standard 79t spur gear would get you FDR = (79/25)*2.6 = 8.22, which is safe for motors down to 10.5turns in a buggy, but might have a lower than desirable top speed for motors >13.5turns.

The FDR suggestions above are based on circuit racing, so if you run on smooth surfaces (on-road) at high speed you can probably afford to run a lower FDR, and if you run on slower rough terrain like grass you might need to go to a higher FDR. If in doubt, start with a higher FDR and see how hot the motor gets. If the motor is running too hot (can't hold your finger on the can for more than a few seconds), you need to go to a higher FDR - a pinion with fewer teeth, or spur with more teeth. If the motor is running cool, you can afford to go to a lower FDR (more pinion teeth or spur with fewer teeth) which will achieve a higher top speed, but slower acceleration. There may be a limit to how small or large of a pinion and/or spur gear will physically fit in the car, so if you're making a big alteration to FDR you may need to change both gears to come up with a combination that physically fits.

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In my TRF201 i simply took thr fan off the 10BL120 ESC and it was fine. For a 13.5 motor i bought a Team Associated B4 72t spur (direct replacement for the tamiya spur) and ran a 27t pinion for gearing around 7FDR. It was perfect. 

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I have a Zahhak which is pretty much upgraded to a TRF201 (and a little beyond).  Here's what I'm using for electronics:

 

  • Savox SC-1258TG Servo
  • Tekin RS Gen2 ESC
  • Trinity 24K 17.5

 

I'll have to check for sure, but I'm either using a 27T or 28T pinion right now.  The motor is not a current top tier motor, but it does really good.

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Okay,  I just purchased a motor and ESC.  Motor shows to be a 3650 4300kv with a shaft that is just over 3mm and the esc says it is a 60amp that is 2s and 3s compatible.  I really only plan on using 2s.  I found a 23t gear that is an option gear that came with my Traxxas Slash.  The big gear is a 79 tooth on the Tamiya.  Will this gear work or should I maybe order a set of other 48p gears to try?  I appreciate all your information.  I have been studying it over and over again getting what I can from it.

Thanks for your time

Jeff

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23t pinion will give you a 8.9FDR which is oretty much spot on for that motor. I would get involved and run it. If the motor is too hot to touch after a few mins running, get a smaller pinion, if it's completely cool then you could go higher. If it's warm/hot thrn it's about right. 

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Okay, I picked up a Flysky gt3c which seems easy enough.  I received my cheap esc, motor, programing card eBay combo.  The motor fit great with no problems but the esc has a fan which I thought would be removable.  I can take it off but the wires are soldered to the board.  If it becomes necessary due to clearance can the wires from the esc to the fan be cut to use the esc without the fan?  I really appreciate all of the help and information all of you have shared with me.  

Thanks

Jeff

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Yes, you can cut the wires, just be sure to insulate the ends so that they don't short as that might fry the ESC. Alternatively, if you have a small enough soldering iron and steady hands, you can unsolder them from the board.

Another approach is to get a very small JST male and female plug and put these on the fan power wires so that the fan can be removed and added at will.

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1 hour ago, jdh6fan said:

If it becomes necessary due to clearance can the wires from the esc to the fan be cut to use the esc without the fan?

Physically, you can cut.  But would it function well? 

If the motor is not demanding (low KV), and outside temperature isn't hot, it could function.  But if KV is high, the ESC will get hot, so you need the fan. Especially in hot weather.  Before cutting, I would try to keep the fan somewhere near.  Blowing air from the side, maybe? 

Even if you cut it, I'd do what @TurnipJF said.  Leave some wire, so you can solder.  If the ESC cuts out occasionally, you know you'll need a fan.  But if the ESC is completely burnt out, a fan can't help anymore.  

 

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With a 4300kv motor I wouldn't get rid of the fan. Can you mount it next to the esc so it still blows on it for cooling?

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I plan on trimming the body this weekend so I can set it on there and better tell how much room I have.  Being able to stand it up and blow on the esc is a real good idea if I can make it happen.

Thanks for the help

Jeff

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I would say that you might need an esc fan with a 4300kv motor on a cheaper 60A esc. Many higher quality 80A and 120A ESCs would have a better chance running that motor on 2S without a fan as they have lower resistance transistors so generate less heat in the ESC. 

If the ESC has overheat protection functionality, then it should be safe to try without the fan - worst case it should just stop running if it gets too hot. After cooling off and power cycling, it'll run again.

Running a higher FDR will make both the motor and ESC run cooler, so could be the ticket if absolutely cannot fit the ESC fan. You can also try mounting the ESC in an unconventional position (e.g. on its side) if it achieves a lower profile. 

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Agree with @nbTMM re FDR + track 

Track also informs ride height, droop + camber 

All of which will push the motor / pinion hard on landings / turns if it’s a fun track 

Fans are a double edged sword re battery choice / life - so again depend on track / race time / motor KV / ESC A

In short, everything above is spot on but it all depends on track / race conditions 👍

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