Hobao/Scorched RC VTE Speed Build Thread

[Diem Turner]

If you beat me to the punch on the road test I’ll be eagerly anticipating your feedback. Pretty sure I’m staying with diffs. It’s all I know.

You can bet on it brother. I've been dying to go out for a spin but it's been wet out the past couple of days. If the weather report is to be believed, it's supposed to be dry for the rest of the week.

One minor update to report on, I wasn't happy with how the Arrma 39T spur sounded so I shimmed up the motor/diff mount and dropped in the 42T gear I initially wanted to use and a 25T pinion. That should give me a top speed of around 65mph for some initial testing. It should also give me sufficient clearing for the 1717/1721 motors (the stock mount was just a hair too low for the 1717 to fit which will go in next paired with an XLX2). So, if all goes well, tomorrow should be the maiden voyage.

 

[Phantom21]

Looking good @Diem Turner!

 

[Dan B.]

You can bet on it brother. I've been dying to go out for a spin but it's been wet out the past couple of days. If the weather report is to be believed, it's supposed to be dry for the rest of the week.

One minor update to report on, I wasn't happy with how the Arrma 39T spur sounded so I shimmed up the motor/diff mount and dropped in the 42T gear I initially wanted to use and a 25T pinion. That should give me a top speed of around 65mph for some initial testing. It should also give me sufficient clearing for the 1717/1721 motors (the stock mount was just a hair too low for the 1717 to fit which will go in next paired with an XLX2). So, if all goes well, tomorrow should be the maiden voyage.

Good approach. I’m tuning in, man….

 

[chris adams]

I'm stupid happy about YOUR car lol. Cheers to the maiden voyage

 

[Diem Turner]

Looking good @Diem Turner!

Thanks man!

Good approach. I’m tuning in, man….

I have to admit, It's really hard to resist temptation sometimes. As long as it's dry out tomorrow I'll be alright for some testing. But I made myself the promise to not make any speed passes unless it's been dry for at least two days running and I plan to stick to that plan. The day after it rains the road tends to feel a little greasy and I'm just not willing to risk a crash just for the sake of making a pass. This week is looking promising though...if the weather report is correct for once.

I'm stupid happy about YOUR car lol. Cheers to the maiden voyage

lol, cheers brother, I appreciate that

 

[Diem Turner]

So a little mini update. My Perfect Pass launch control came in today. After testing the functionality I wrapped it up in a couple of pieces of shrink tubing, cut a hole for the trim pot and mounted it on the receiver box with some Dual-Lock (I have the same spot outfitted with Dual-Lock on my Infraction so that I can swap it between cars). Why shrink wrap it you may ask...well, I've seen a case where, after a crash, the trim pot vacated the PCB rendering the module non-functional. So I wanted to ensure that, in case I total my car out, I'll still have a shrink wrapped PCB to look at. Well, not really. Just this little thing is kinda pricey and I wanted it to last as long as possible.

 

[Diem Turner]

Before getting too deep into the build, I decided to test drive the car with the F/R diff lockers in place to see how I got on with them. I'd never run them before but was curious to try them out as they were all the rage in the speed run scene a year or two ago. As they say, never know 'til you you've tasted it.

In a word: No. Totally not my bag. I can only describe the feeling of the car as "wooden". Having a poor turn radius is one thing. But you can feel the car struggling to make a turn with all four wheels turning at the same rate. Maybe they'll make sense on drag pulls? Dunno, but for speed runs I'm sticking to center spool and diffs F/R. So I broke the front and rear down and rebuilt the diffs with 10k in the front, 30k in the rear.
+

While I had the front disassembled, I set about installing the headlights. I had tested them out but the switching was a bit wonky with the Spektrum ESC. The BEC was probably still set to 7.4V and the light switch's operating range is 4.8-6V. My Spektrum field programmer is broken and I just cannot be bothered to count beeps and program it like a morse coder.
So out went the original plan of using the Spektrum 150A ESC/4074 for testing and in went an XLX2/1717 1650KV combo. I ended up taking my time with the light install and I'm happy with how it turned out. I put a little strip of aluminum tape on the foam bumper to glue the light fixture to and then got to work on hiding the wiring.

After feeding the wiring through the bumper assembly and over the shock tower, I secured a 600mAh 2S battery to the steering plate with a little Dual-Lock and from there routed it under the servo and into the electronics box. It's close enough to "wireless" lighting for my purposes.

 

[chris adams]

Lookin gooooooood brother, like really good. The light install looks primo.

 

[Diem Turner]

Chassis layout after install of all electronics.

I relocated the ESC switch to the rear bulkhead for easy access when the body is buttoned up.

I applied four layers of LiquidMask with a brush last night and let it cure overnight. I didn't really like the panel lines/windows on the Dome body, so I just put them where I thought they belonged. It definitely has some strangeness to to its physical features, but I like it.

After working out a livery and deciding on what color will go where, I settled in with some Tamiya Clear Pearl, Neon Pink, Cherry Red, Smoke, gold and white. I finished it up with some 2mm and 4mm tape to create borders between the colors and frame the windows and threw in a smattering ofd decals of real world sponsors and RC related stuff . I kept it minimal, but tried to get a little bit of that race feeling.

Traction duties are taken care of by the GRP GTK-XM7s that I had painted for my JOTA body and some blue wheel hexes.

I took her out for a test drive as soon as the body was done to see how it do. In a word: lively. lol...This car immediately put me in mind of the Lancia Stratos Group B Rallye car. Very agile with the short wheelbase with a healthy offering of oversteer. I'm going to swap the front and rear diffs, I think that should settle it down a little. I had to do a fair bit of throttle delay and expo tweaking to get it to behave a little better but all in all, I think she's going to be an awful lot of fun. Actual diffs front and rear are hands down better that diff lockers. It's not even close (for me anyways).

One last thing I thought was worth mentioning are the body posts. I'm not really sure what Hobao was thinking with their design. I can only surmise that they designed them based off the assumption that you would only have one body for the car and never have a second or third. If you are to use them as supplied by Hobao (two piece, a stalk mounted to the shock tower and "sliding top caps" for lack of a better term), you'll need to cut both the stalk and cap to lower the body. If you cut off one hole position too many on accident....well, that's one less body mount you now have (unless I'm totally misunderstand how they're supposed to be used, but I don't think I am).

So I simplified their unnecessarily overwrought design, took the foam pads and eliminated the "sliding top caps" altogether and decided to just use the stalks as a more typical, run of the mill body post.

I think my only two gripes with this car are the oddly constructed body posts and the fact that you have to remove the motor/diff mount from the chassis to service the pool which was kind of an odd choice on Hobao's part. It's not a deal breaker or anything, just feels like last century after seeing a stock Arrma 5S motor/diff mount. Oh and the screws that you tighten down the sliding motor plate with are...I think anemic is probably the kindest thing I can say. It was definitely a reminder of how much better some thing like a PPS mount is.

One pic comparing the Infraction GT setup with VTE GT. The proportions of the chassis are different enough that the VTE looks like it's noticeably wider than the Infractin..but it's just an optical illusion.

Diff swap is in progress. I hope I can try it out here in a few before the rain starts. Oh and this car is sooo much easier to pick up and carry by the body. The rear end of the Dome body is super rigid (and of course the fact that this weighs a couple of pounds less helps as well).

I think I'm also going to try the softer shock springs. These stiff spring are a bit much at this weight. I would't be averse to it being a tad more supple.

 

[chris adams]

The body came out fantastic. It's a bigger size difference between the two than I thought it would be but I guess if you only look at wheelbase it's more reasonable. I'm sure that thing is gonna be a low volt rocket by the time you get it all sorted.

 

[Diem Turner]

Thanks man. I didn't put too much effort into it. Since I'll be gathering my first experiences with this car, spending too much time on detailing a body that is sure to kiss some curbs and experience the one or other hard prang seemed like a poor use of my time. I've got a good feeling about it too.

 

[LibertyMKiii]

Great work so far.

+1 on Hobao's motor mount/center sucks! Also seems weak metal. PPS is considerably thicker.
Agreed with your assessment of the body mounts. My conversion to the 1.25" quick connect mounts was a big hole to put in a body but have found I like it.

 

[dk10438]

Very well done!

 

[Diem Turner]

Thanks fellas

Yeah, the motor/diff mount is a little unsatisfactory. But help is on the way. I put a Roto-lock in my shopping cart on Friday. Very much looking forward to trying it out. I went with the diet version of the mount as I really don't anticipate dropping a big block in here....ever.

 

[chris adams]

Man a little tp4050 or 4060 high kv cm motor would be awsome in that light thing. look into their eyes now say "tp 4060, Tp 4060, tp 4060"

Now I just have to water

 

[Dan B.]

I just went over this build again, and wow. What a beautiful build. I somehow missed the fact that you chose a Futaba CB500. I’ve heard it’s one the best out there. How are you powering it?

 

[Diem Turner]

I just went over this build again, and wow. What a beautiful build. I somehow missed the fact that you chose a Futaba CB500. I’ve heard it’s one the best out there. How are you powering it?

Not gonna lie, it's a pretty nice servo. Don't ask me why I thought this, but I felt like it was a little underpowered for the Infraction (not that I ran into any issues with it before switching to the HRC servo) and I got this thing in my head that more torque equals better directional stability at high speeds, resistance to bump steer, etc. so I decided to go with the 44kg servo. The front kick-up automatically tries to force the wheels to point straight ahead so I wanted heading holding power.

On the VTE, the steering has far less (none?) tension in the steering geometry because it has no kick-up so it requires much less force to turn the wheels and hold them at whatever angle you have them at. As for power delivery, nothing special. I'm just running it at 6V straight off the receiver. I don't have the AUX wire from the ESC connected so I'm limited to 8A max from the BEC but I'm not getting the sense that this is in any way insufficient for this application.

The programmability of the servo (neutral position, speed, dampening and some other variables) is a nice added feature that allows me to do things like center the servo before even touching parameters like sub-trim. Is it strictly necessary? No, definitely not. Is it a nice touch that allows you to dial your steering in even closer to an imagined ideal? Yes. This servo is stupid fast and being able to tailor it to any given use case is pretty sweet. Now...is it $180 sweet? That's definitely debatable and even I'd tend to lean towards saying "probably not". But once you've rolled the price of it into an entire car...you tend to forget what you spent on it and just see the net positive of the additional features.

 

[Diem Turner]

So here's a quick video from a few hours ago. It was a balmy 21°F and the misty air under the street lighting took on a surreal look on video. I wish I could order up weather like this sometimes.

 

[dk10438]

yeah the CB500 is a sweet servo and once you're used to the Futaba eco system it's hard to go back. I love being able to set the neutral point and end points and not having to mess around with the sub trim. A

 

[Dan B.]

So here's a quick video from a few hours ago. It was a balmy 21°F and the misty air under the street lighting took on a surreal look on video. I wish I could order up weather like this sometimes.

It seems like it’s tracking very well. How are the winters there? Obviously cold when you ran it. Are you going to have to shelve it for the season? If so, that must be really frustrating after all of your work!
Also, why don’t you connect your AUX wire in the receiver?