Build Thread Kaladeth's Mecatech FW01

[kaladeth]

Intro

This is my first 1/5th scale on-road gas car. Will post build details as well as pre-race and post-race notes.

Table of Contents

Shopping List
Battery + Charger
Receiver
Servos
Radio Setup
Body
Rear Wing
Fuel
Ride Height
Engine
Tires
Setup
Corner Weight

 

[kaladeth]

Shopping List

Amazon

• Ratio Rite Cup
• Motul Kart Grand-Prix 23000 RPM synthetic oil
• Mobil transmission fluid
• Wera 4 5 and 6 mm hex T drivers
• Uni foam filter cleaner and oil

Lowe’s

• VP 4 stroke fuel 1 gallon (*ethanol free)
• 1/2” 12 point 17 mm socket
• 3/4” melamine board, 2’x4’, precut hobby section

Rcmodelsport

• PMT Treaded Tires (supersoft rear, soft front)
• Futaba 10PX LE

Fgsupply

• Kit + Diff + Airbox + Clutch + Pipe
• Clutch tools
• Engine
• Rear wing
• Tire warmers
• Toe blocks
• Exhaust deflector
• 34 pinion
• Clutch bell

Napa

• DOT5 brake fluid
• https://www.napaonline.com/en/p/NBF45032

Jersey Modeler

• 2.5 gallon fuel pump RHP
• https://jerseymodeler.com/index.html

DDM

• Carburetor
• https://www.ddmracing.com/

Amainhobbies

• Shorty 2S Battery Pack
• 2S Charge Cable

Ogio

• Travel Bag
• https://www.ogio.com/travel-nav/travel/ogio-bags-travel-2017-rig-9800.html

 

[kaladeth]

Battery

2S 6400 mAh LiHV

Charge Cable

2S Charging Cable, 5 mm bullets with 2 mm balance pin. I have a cable on order, but couldn’t wait so I made my own to tide me over.

 

[kaladeth]

Receiver and Servos

Managed to fit a Radiolink R8FG in there, along with the MyLaps transponder.

From Car Left to Right	Wire Label	Function	Radio Channel
Servo A	“2”	Throttle / Rear Brake	Ch 2
Servo B	“1”	Left Steering	Ch 1
Servo C	“3”	Right Steering	Ch 3
Servo D	“4”	Front Brake	Ch 4

The servos are Futaba CB701, max 8.4V.

• 0.075 sec/60° at 7.4V
• 680.5 ozf/in at 7.4V

Radio Setup

Two servos are used for steering. Two ways to hook them up: (a) use a Y cable and only use Channel 1, or (b) put one on Channel 1 and the other on Channel 3.

I went with (b) so that it’s easier to zero the servo with the radio's subtrim function. I used steering mixing to achieve this, but do not plan to adjust steering endpoints on the fly at this time, to keep it simple.

For brakes, Channel 2 is both throttle and brake (brake1/rear brakes). Channel 4 is brake2 (front brake).

To adjust brake bias while driving, I assigned DT3 to adjust the front brake endpoint, and DT4 to adjust the rear brake endpoint.

 

[kaladeth]

Body

Alfa Romeo body with front bumper. It's good to put gorilla tape along the wheel wells to protect the paint from the tires, as well as reinforcing the body to minimize tearing (e.g. tape on the mounting post areas, etc.). Additionally adding a cf plate along the side mounts helps as well.

Rear Wing

Had to drill four holes in the body, and two holes on the carbon fiber mount plate.

Ideally should be set the most vertical for maximum downforce. Still learning if this current setting achieves that.

 

[kaladeth]

Fuel

Need to get (VP Racing) ethanol-free 4-cycle gas, and mix with 25:1 Motul 2-stroke kart oil.

Fuel Can with Pump

You will need something to transfer the fuel to and from the car's tank.

I considered buying the pre-made one from Jersey Modeler, but they no longer sell the 1.3 gallon one, and the 2.5 gallon one seems too big, so I decided to build my own.

Will base it on this how-to video:

Raw materials:

Fuel Nozzle

It was tricky for me topping up and transferring fuel to the can. This blue fuel nozzle from Lowe’s is a god-send.

 

[kaladeth]

Ride Height

To set ride height it's helpful to have a rigid and flat setup board. Tempered glass is best, but is heavy. I went to Lowe's and got a 2’ x 4’ melamine board, and cut it down to 24” x 30”.

Entirely optional but you can also apply melamine edge tape to the edges to make it look nice. I went with white but next time will go with black.

Starting with 9 mm front and 10 mm rear:

Need to mount the tires of course. The nuts require a 12 point 17 mm socket. Once it’s tight, the set screws need to be screwed in until flush with the outside of the nut.

04.03.2025

Upgraded my melamine setup board to plate glass!

 

[kaladeth]

Engine

The second hand car I bought had a modified engine for expert class, so in order to drive in the beginner class, I needed to swap in a stock motor.

> Zenoah G230RC 2.8 HP Engine

For break-in, run it on the ground for about 15-20 minutes at idle and every so often open it up to clean out the exhaust.

 

[kaladeth]

Tires

I will start off with treaded PMT, with super soft in the rear and soft in the front.

As the season progresses, will probably switch to PMT slicks, and eventually to harder compounds, e.g. medium all around with maybe a hard in the front left.

<space reserved for tire history and takeaways>

 

[kaladeth]

Setup

Shocks: Front - 6000wt, yellow spring. Rear - 4000wt, red spring.

Ride height: 10.0mm rear, 9.0mm front

Droop: 50.0mm front, 46.0mm rear

Toe: front - 1.0 toe out both sides, rear - 3.0 toe in

Front camber: 0.5 degree positive left, 0.0 degree right

Sway bar: 2.75mm front on 3 dot, 1.75mm rear in 2 dot

Front caster: 6.0mm spacing front of arm, 3.0mm spacing rear of car

<space reserved for setup>

 

[kaladeth]

Corner Weight

TBD

Weight with no fuel: 22 lb 5 oz

 

[332_RC]

Wow! Awesome machine!

 

[Tunedfrog]

In my opinion, 1/5 scale gas rigs is as cool as it gets.
Looks great @kaladeth

 

[332_RC]

Man this build is amazing. What's the target speed of a RC like this?

 

[kaladeth]

Man this build is amazing. What's the target speed of a RC like this?

On the track it should be pretty similar to an Arrma Limitless. I haven’t timed it yet but on the straight I expect it to hit 50-60 mph.

That said I heard the record lap time on this car is 15 seconds. I can only do 18 on my Limitless right now (maybe inch to 17 this year!).

 

[332_RC]

That's really amazing. A big 1/5 scale over 60! I guess the weight can actually help 'set' the car in the corners like a 1:1.

 

[kaladeth]

<Reserved for Practice Weekend / No Points Race>

 

[kaladeth]

Race Day #1

Got to race with the big boys today.

The race day started off with a mad rush to install two new steering servos.

I messed up Q1 because a small crash (side-to-side entanglement with another car) tore up the body, and last minute tuning turned out to be bad (too lean?). Idle was too low also - so when the crash happened the engine died. Not to mention I did not fix the battery connection properly so the (+) got pulled out. All noob errors.

Both were fixed before Q2. The car ran mostly fine but I noticed braking hard started to pull the car to the left. Cleaned the rear disc brakes and hoped for the best. Apparently these are usually replaced after a day of racing.

Here’s how they look New / Clean:

This is after about a day of racing. After cleaning already. It’s toast.

The car was not running as nice as it did during the no-points race two weeks ago. A lot to learn.

Mains went as expected. I managed to stay out of the way of the fast cars, not crash, and finish.

Right at the end, the car lost power (giving throttle would spin the motor but would not engage the clutch). Got some wrenching to do to figure out what’s going on!

And just like with the Arrmas a year ago… I need to work on improving that consistency too.

Fast Lap: 19.873 s

 

[kaladeth]

Race Day #2

Practice was crucial yesterday. Determined the clutch had to be rebuilt. The clutch bell also had some grooves in it, so it got replaced too. Massive lap time improvement, from 25 sec to 20-21 sec.

Worn out clutch:

Replaced springs and shoes:

Practically new! Hopefully lasts for several race days:

In the qualifying rounds, the car was feeling really good (finally!), but I didn’t really push especially with the old tires. Also in Q2 the + terminal of the battery got unplugged again - adjusted the bullet to make it tighter, will be upgrading to the new 1Up bullets soon. Ended up in P5 at the start of the mains.

The Mains was super fun. Stuck in fresh GRP slicks. It was a close race with many exciting moments. It wasn’t the main objective today, but I finished in 2nd place!

Fast lap: 18.667

 

[kaladeth]

Pretty easy brake maintenance. Just need to be careful with the two small springs.

The left rear axle quit on me while doing a simple turn at Turn 10 leading up to the straightaway; was a pretty easy fix. Replaced the brake disks (both left and right rear) because the left got dragged on the ground when the wheel fell off.

Had some trouble starting the engine. Checked the spark plug. Mix might be too rich.