Digital.Complex: [done] RC18T2/B2 - Digital.Complex

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[done] RC18T2/B2 insane brushless

#1 User is offline   aotsukisho 

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Posted 22 July 2010 - 11:24 AM

as you may or may not know, I bought an RC18T2/B2 kit when it first came out (late April). I was very excited, up until I realized I didn't have enough funds to complete the project at the time lol. Right now it's sitting in one of my cabinets fully assembled with a CM2042 (Castle Creations 1:18 motor, 4200kv) and a slightly worse for wear C1016 servo (stock RC18). Upgrades include steel CVA's and Traxxas 1:16 Revo tires on 12mm hex adapters, but unless I figure out how to stop them rubbing I can't use them.

I made a very large Excel spreadsheet with all the batteries on Hobby King for my reference... it appears I will be using (cramming) 2200mAh 5s or 6s batteries. 5s will give it 277W, which is exactly the same as my old buggy, but this time it has a relatively huge battery and much higher voltage.

I plan on using the Mamba Max Pro to power this project. I have to do some minor chassis modifications to make it fit, but the good thing is that I'm only using 20% or so of its current handling capability, and therefore I'm confident it will run happy without the fan attached.

I do have to buy new wheel nuts, as the stock ones in the kit suck ass. They are steel and the internal threads don't start til a mm or two inside the hole, so I can't use wheel spacers. If I can space things out 2mm or so, I can use the Talons.

As I now have another receiver to put in the chassis, this project is open again.
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#2 User is offline   aotsukisho 

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Posted 07 September 2010 - 08:35 PM

Update on the project. First, the pictures.

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Replacement front gearbox came in. :D

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I learned my lesson lol. Using my reamer instead of the drill press this time... :oops:

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nice and precise.

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this is actually the stock tensioner pulley shaft taken out and screwed into the bulkhead.

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great! it works.

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side view, it clears the steering drag link.

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view of the entire drivetrain

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the pinion is still very close to the belt though...

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but it's a little bit better.

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prepping the batteries.

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I found out that the CM20 has a set of holes that is perfectly spaced to do a custom motor mount job. This mounts the motor very low in the chassis, which improves CoG (slightly...) but more importantly gets the pinion farther away from the front belt.

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side view.

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reamed the body, test fitting it.

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final layout of the guts.

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other side. cute, the GSR ESC with stubby little wires.

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pain in the ass rear-exit motor wires. Have to clamp them to the motor so it doesn't make the truck body bulge any further.

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sexy body painted with Parma Metallic Red. came out nicer than I thought it would.

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I thought I did a good job with the window masking too

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but the goddamn window stickers made masking pointless. Oh well.

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overwrote the 'AE' on the front grill. :cool:

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in hindsight I kinda regret putting the decal there, I may have to change this into a truggy so I can control it while driving lol.

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ready to go

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kind of easy to tell that the body is bulging slightly. also yeah...the alignment is out slightly. I fixed it.

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and off she goes!

Keeping the stock battery strap was a challenge, I could've just gone with tape like my first RC18 but I decided to see if I could use the newly designed strap in my setup. I replaced the stock screws with Traxxas Revo 3.3 brake caliper screws (M3xsomething, with a long smooth section) and drilled a hole straight through the strap latch. The latch is held up by an Xmods stock spring (they're so damn useful!) and the height is still adjustable since there is enough thread in the chassis to be able to raise/lower the height of the strap.

I used Deans Micro on the batteries and 3x series battery harness due to the small size, and the harness mates to the ESC with a Deans Ultra 'just in case' I decide to run the RC18-2 with a different battery (my old 2s 2200 35C fits perfectly in the battery tray). Wire management was difficult too, due to the fact that there was also three sets of balance taps to untangle while fitting the battery in.

There was severe starting issues with the MMP straight off the bat. I tried changing everything (timing, starting power, even the throttle curves and reversing the motor) but it turns out that it was the firmware. 1.27 and 1.26 both have the startup problem, where it seems to be stuck in ramp-up mode for a long time. The car had to be rolling faster than 4mph or so before the throttle worked properly. Changing the firmware to 1.25 solved that problem, and it works perfectly.

I think I will have to buy a 60t spur gear, so it will slightly help with the gearing...and maybe some 1:10 buggy tires, if I can't get the 1:16 Revo ones to work. I'll try getting better wheel locknuts that 'bite' better, and maybe with the help of some spacers it'll be good.

Differential Ratio: 2
Transmission Ratio: 1
Other Ratio: 1
Spur Tooth Count: 55
Pinion Tooth Count: 12
Total Voltage: 22.2
Motor KV: 4200
Tire Diameter (inches): 2.4
Tire Ballooning (inches): 0
Motor Current Draw: 16
Motor Coil Resistance: 0
Spur/Pinion Ratio: 4.58 : 1
Total Ratio: 9.16667 : 1
Tire Circumference (inches): 7.54 inches (191.51 mm)
Rollout: 0.82:1
Total Motor Speed: 93240 RPM
Vehicle Speed: 72.63 mph (116.66 km/h)
Effective KV Value: 4200
KT constant: 0.32 oz-in/A
Motor Torque: 0.03 ft-lbs
Final Torque: 0.25 ft-lbs
Final Power: 355.2 watts (0.5 HP)

Here's the lowdown on the motor and gearing.
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#3 User is offline   aotsukisho 

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Posted 31 October 2010 - 11:44 AM

in the meantime, this project has taken a different turn...it currently has a limited-edition Castle CM26 series motor running on 'just' 2s lipo. It just needs a proper 1/8" bore .5M pinion. Due to it not requiring 6s anymore, I swapped the Mamba Max Pro with a Sidewinder I sniped on eBay for $40 shipped.

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it actually fits better than the MMP, due to where the wires exit the ESC

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as per usual, debadged with a GSR sticker
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