XRay T4 2019 Review Pt3 - Build and Tips for Stock Racing

Continuing the XRay T4 2019 build and review extravaganza, this part will cover how I built the Stock runner and the option parts that I used.

Stock preparation

Preparing a stock car is a bit different to a modified car. A stock car seems to have more steering then a modified car. A good stock car needs to have enough initial steering, but also a lot of corner speed. Too much steering on a stock car would kill the corner speed.

In order to create the most efficient stock car I concentrated on the following aspects:
  • Lowest possible weight – best possible acceleration, plus possibility to add weight where you want it to be.
  • Lowest possible un-sprung mass.
  • Lowest possible rotational mass.
  • Lowest possible center of gravity - increase in corner speed
  • Least amount of friction

Lowest possible weight

The T4 is a quite lightweight car,  It is under the 1320g weight limit already in kit form. However I wanted to make the car as light as possible to give me more options on weight balance.
Titanium screws shave roughtly 30% weight of a steel kit screw

I added the Hiro Seiko aluminum screw kit (gold one this time) and Avid titanium ball studs. The aluminum screws and ball studs also help you to lower the CG, whereas the ball studs also have a beneficial influence on the un-sprung mass. Also an interesting option are the titan pivot pins (307322 and 307222).

Lowest rotational mass

It is super important to limit the rotational mass as this has a beneficial influence on the car’s acceleration. In the stock class, where the cars are evenly matched, this might give you an advantage.
These nuts save 0.15g from the kit version
The lightest possible wheel nuts I could find are the Triad M4 Light Wheel Nuts. They come in a variety of different colours and only weigh in at 1.5g for 4.
Titanium screws shave roughtly 30% weight of a steel kit screw
The Xray drivetrain is one of the lightest around, and it’s very hard to shave off weight. When paying attention to the diff, there are 2 areas where you can save weight. The standard screws only weigh 0,9g, but the titanium Hiro Seiko ones I used are slightly lighter at 0,6g.

I also opted for the Xray graphite gear diff gears (Xray 304932) which are fractionally lighter then the stock ones (1.23 vs 1.29).

The front spool is quite light as it weighs only 10.45 grams.

However we can go lighter. I replaced the kit parts with (Xray 305136)  Alu solid axle driveshaft adapters  and a 10mm alu screw (be sure to use some oil on the screw or thread a steel screw in the plastic first, otherwise you might round off the hex). I also used the (Xray 30542) Orange strong drive shaft caps. The result is an impressive 10% saving as you shave off over a gram.

Lowest possible center of gravity

This was an easy one. Florian was running the Gensace 7500 RS batteries. The extra capacity of the battery keeps the voltage more steady towards the end of the run. Most top drivers however use low center of gravity batteries. The faster corner speed is more important than the higher capacity.

We switched from Gensace RS7500 batteries to the lighter RS6000 batteries. On the fastest lap-time, there was virtually no difference, but over 5 minutes the car was easier to drive fast with the lighter batteries.

In order to compensate for the lighter weight, I used some great 7075.it product: the 8.5 gram servo mount insert, the brass battery mount system and the new 30g center weight. I omitted the weight under the electronics that is only used to balance the car with the heavier battery.

While looking at the car, I also decided to ditch the 3mm floating servo holder. This part weighs almost 5grams and I replaced it with the 2mm graphite chassis stiffener (Xray 306530). We haven’t tested the car yet, but I think it will be ok to run it.

Least amount of friction

To reduce the friction to a minimum, I also opted for the alu adjustment ball bearing hub (Xray 302063) as it ideally positions the ball bearing for the drive train.

Instead of the standard belts, I used the low friction Kevlar drive belts (Xay 305447 and Xray 305434).

Other ideas

Last time I used some shrink tube around the servo cable to shorten the cable. On the stock car, I glued the shrink tube on the servo (using Hudy body fix) so that it’s less noticeable.

Monaco RC also makes a neat air conveyer (MC-AC40) for the cooling fans. This air conveyer conducts the air around the motor to keep the temperature down. To be honest, I always messed up the cabling of the cooling fan.

With this air conveyer, you get an orange insert that allows you to rout the wires either to the top or down the bottom. I decided to go the hard way this time and routed the wires over the motor mount and then towards the Hobbywing XR10 ESC. It looks smart and hope it will keep this way :)

The Stock Xray T4 2019 is now complete.

The drivetrain feels really smooth and free and I was able balance it perfectly on the scales.

Our first test with the T4 19 will be the EWS, quickly followed by the ETS in Vienna. We will start with the setup from the 18 car and fine tune the car from there.

Impressions so far

The Xray T4 2019 has impressed me so far. The quality of the components is superb and it holds together really well, even after some hard racing.

Florian has improved on his times that he had previously set with the 2018 chassis. The chassis responds well to the different set-up changes that I have made to it, and it provides a wide range of different areas that can be tweaked and refined to accomodate specific track conditions or layouts.

There is still a lot more speed to come from this chassis, be sure to check back as I will post further findings and set-ups over the coming months.

Special thanks to:
Xray 5314432131455241013

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