INVADER - Nitro Slash drag car

[Doom!]

That looks so different with that shorty cooling head.

 

[johnnydmd]

That looks so different with that shorty cooling head.

Yeah, it sure does, and I never liked the look of it which is why I waited so long to do it. But I needed to solve a problem, so here we are

I ran it last night some. Seemed to warm up a bit faster, and even after 10 minutes of running it didn't get too hot.

 

[johnnydmd]

More weight loss. Changed out the Vanquish OMF Outlaws for some ultra lightweight alloy wheels and these new tires that ProLine Makes. Lost another 100 grams. Car now feels very noticeably lighter in my hands.

Probably notice, maybe not, there is now a gyro in front of the receiver. I am fully aware that many events don't allow them (though I really tend to think that's a silly rule, among other silly rules that I'll not get into on this thread but maybe some other one). It's easily disabled in those instances. Reason I put it there? Why not use all available tech to get the fastest run possible? Now I'm able to turn things up a bit more.

A look at the new front wheels:

Also, I tried my hand at carbon fiber stencil painting on the front canards:

Kinda cool I think.

Sunday is our next TNT. It's going to be in the upper 70's, so should be able to get some decent hits and data.

I have a Force .38 arriving Friday that is earmarked for one of my MT's, but if I have time and get it broken in Saturday, I might do a few hits with it in this car just to see what it can do. (hopefully not blow up the entire drivetrain).

 

[Doom!]

This is still one of the coolest RC's I've ever seen. Good luck Sunday!

 

[johnnydmd]

Tested a bunch Sunday. Gyro worked very well. It was dusty (pollen everywhere) on the track). Tough conditions, no matter how much we tried to clean.

I backed off the throttle tune a good bit. Still had to drive it, and the response was a little too slow. Went back to the "hot" tune and just decided to peddle it the entire way. Had a couple of good runs, but little concerned that the tires were shaking loose even at 100ft when I tried to juice it to hold off or run down anyone. Noticed another thing - the rear wing was flopping pretty hard at high speeds.

Thinking I needed to kill two birds with one stone here. The Viper ACR Extreme Aero is the king of downforce. Most of the drag/roll Viper racers use it. So I've swapped out my custom spoiler struts and used the BittyDesign factory ones in hopes of creating more downforce so that I can open up the throttle more after 60ft.

It definitely changes the profile of the car a bit. These struts also have a lot more support, so the wing will stay stable.

Hate making a change so close to race day, but felt I had to do something there.

I also will do some wind tunnel testing with the corner weights to see the difference between the two wings since I have the other body still using the custom strut design.

 

[ahr43]

Looking good and good test session report. Little practice on throttle disciple will come in handy on those hot days when the asphalt is greasy.

Ha. Mention of pollen brings back memories. Especially in the March time frame every year there'd be a light dusting of pollen on the workshop floor. Was great for checking rear tire footprint after cutting a set of foams. Dry rolling the chassis on the shop floor it'd lay down a nice clean tire contact print.

Good luck at your first event. That's when you'll really need to see what has to change. Usually at the end of the season for me, the car looked and set-up entirely different than from when it started the season. Keep up the good work and thanks for keeping us in the loop. Cheers. 'AC'

 

[johnnydmd]

Results in

Wing was good, definitely helped on the top end traction.

Gyro was bad. It was acting weird. When I first installed it, I had to correct the steering pretty far to the left to center things. This day, it somehow flipped and had to correct in the opposite direction. At the end of a run (defeating a brushless car), I completely lost steering, and didn't have enough braking power (I set it low intentionally), or enough time/space to deploy the chute. Hit a curb, jumped over it and hit a light pole. As I walked to the car, I fully expected it to be shattered, but was very suprised, and happy, to see that there was only minor damage to the body, and the front bumper on the chassis. The splitter was damaged but still usable, so I took the gyro out, replaced the bumper, and got back to racing.

Treaded Dotek tires, bad. Granted, it was 60 deg, breezy. But I was getting next to no traction, felt like driving on ice. Decided to give the Mambo slicks a try for the first time. Huge, huge difference. I'd say it had a "violent" launch, wheels snapped up hard as I've ever seen one of the cars do it, slammed the bar, then back down really hard, and bounced back up. So that's that, sticking with the Mambos.

One more run, after racing the Mustang a couple of times (also, that car did really well, for the most part). Another brushless car, Drag Slash. Sun went back in, it was cold again, messed with my tune due to the temp dropping so fast. Got it sorted out and ran. I felt I was going to overmatch him, so I left pretty soft this time, a bit rich too. Got out on him but really had to drive it as I was losing traction again in the colder temps. It had been about 20 minutes since the last run, and I somehow didn't notice that water had seeped up through the road near the finish line in my lane. Went right through it, and instantly the car went sideways and barrel rolled and skidded on the roof about 50 feet or so. Body was definitely no virgin now, lol. Good amount of road rash on the roof, faux blower, and front fender. No chassis damage though. Ran the Mustang a few more times after that, but it was getting really chilly by now and cloudy. Rain started.

Got home, got some 400 grit sandpaper and buffed out most of the road rash, then hit it with 1000, then polishing compound. Fixed the blower and re-epoxied it. Fixed the broken splitter with some JB Weld and a brace. Not too bad considering how bad the wrecks were. Can't even tell on the roof, little bit around the left headlight where it was close to the sticker I didn't want to mess up. Good enough

Next get together is a few weeks away, team list/grudge racing. Hopefully it'll be warmer, and we can get some better passes. Both nitro and brushless cars struggled with traction. Overall, it was pretty evenly matched between the brushless and nitro cars, though the big block nitros were definitely the cars to beat.

I have a lot of work to do on my cars. Need to tear down the Nova's engine and fix what looks like a big air/fuel leak. The Mustang has something going on with the steering not re-centering. Viper just needs to be re-assembled and fine tuned. Need to turn up the braking power in that and the Mustang. Rest of the team has a lot of things to fix too.

 

[Doom!]

Good to get all the quirks taken care of early in the season. And you got your crashes out of the way too, should be good from here on.

 

[Chubaka]

Sometimes when your doing too good you need to be knocked down. Makes it fun and keeps it interesting I guess.

Glad everything's OK and still in working order. What polishing compound do you use?

 

[ahr43]

Great race report. Yeah, stuff happens when you're really racing. Relieved to read damage was not too severe.

Racing a cold track can be just as unforgiving as a hot track sometimes. Traction window b/w too hot and too cold is pretty narrow. Hard to tune to. Electric or nitro.

Agree with dialing in more radio brake. Always good having a back-up system to the chute. Couple of guys tried chutes on their electrics back in the day. Found deploying the chute tended to lift the rear clear of the track when popping open. All that weight that transferred to the RR tires on acceleration suddenly transfers back forward when shutting down. Making the rear even lighter and easier for the chute to lift the rears clear of the track.

You'll get locked in, though. Hang in there. Cheers. 'AC'

 

[johnnydmd]

Sometimes when your doing too good you need to be knocked down. Makes it fun and keeps it interesting I guess.

Glad everything's OK and still in working order. What polishing compound do you use?

I use Maguiars Ultimate Polish. The Ultimate Compound is good to use just before that.

Great race report. Yeah, stuff happens when you're really racing. Relieved to read damage was not too severe.

Racing a cold track can be just as unforgiving as a hot track sometimes. Traction window b/w too hot and too cold is pretty narrow. Hard to tune to. Electric or nitro.

Agree with dialing in more radio brake. Always good having a back-up system to the chute. Couple of guys tried chutes on their electrics back in the day. Found deploying the chute tended to lift the rear clear of the track when popping open. All that weight that transferred to the RR tires on acceleration suddenly transfers back forward when shutting down. Making the rear even lighter and easier for the chute to lift the rears clear of the track.

You'll get locked in, though. Hang in there. Cheers. 'AC'

Chutes are very tricky. Need to be level, or slightly above axle. Absolutely need to shape it like an X and cut the center out. Putting a choke on is key too, and knowing where to set it so that it deploys more slowly and doesn't jerk the car hard. I definitely had a few mishaps last year when first using them and figuring out how big to cut the hole, where to put the choke, etc.

Good points about the weight transfer! I noticed that too, one reason why I like having the CF splitter, that thing acts like a ski almost, keeps the front from digging into the pavement when slowing down.

 

[johnnydmd]

Couple of pics from race day.

Getting ready to race a brushless car. Won easily without having to push it too hard, though I really had to drive it anyway.

Edging out another brushless car that was pretty fast. This is the pass I lost steering on right after crossing the finish line. This pic really shows that the wing is putting some big downforce on, as the car is squatted down pretty low, wheelie bar nearly touching.

 

[ahr43]

Green and clean all the way. Win light in johnnydmd's lane! Nice win.

Gotta love the 'One Way' sign in the background.

Curious? How are you powering your steering and throttle servo's? Any other power draws in the circuit besides the two servo's? 'AC'

 

[johnnydmd]

Green and clean all the way. Win light in johnnydmd's lane! Nice win.

Gotta love the 'One Way' sign in the background.

Curious? How are you powering your steering and throttle servo's? Any other power draws in the circuit besides the two servo's? 'AC'

LOL, just saw that sign

I use a 7.2v NIMH hump pack. It was fully charged, and there's no other draw. I lost the steering because the servo horn came loose and was stripped. I don't know if the gyro had "flipped" back and caused the strip, or what really happened. It was one of those horns that uses a plastic insert adaptor to match up the teeth. I promptly ditched that thing for an aluminum one that was a direct fit.

 

[johnnydmd]

Ditched the foam block inside the body to try something else. Was going to run body posts from the front bumper, but really didn't want to cut into the body up there, so I figured I could use posts and some rubber tube to make supports. Yeah, this works a lot better than the foam, and the previous attempt using a 3d printed brace. I might even replace the rubber tubes with some Year Racing body supports and foam glued to them, might be a more elegant solution. I've also got some Baad Racing performance cut wheels on the way for the rear. Will re-weigh everything after.

 

[johnnydmd]

I was messing with the car Friday and I noticed something that I should have seen a long, long time ago, especially because the problem was found in my first batch of chassis (which I had to replace the part) - and that was that one of the holes for the rear suspension mounts was slightly off, causing the right rear wheel to have more toe-in that the left. Since I'd been using a prototype the whole time, I don't know why it never dawned on me that it had the problem too. I'd been kinda meaning to upgrade to one of my newer chassis versions anyway, so I tore it apart.

Put humpty-dumpty back together in a couple of hours.

Came up with a better receiver battery mount solution as well.

I also got my Baad Racing performance cut rear wheels, which save a huge 80 grams of weight from the plastic JC Starfish wheels (pretty shocking actually). I was supposed to get them black like the fronts, but they had some issues with anodizing, and it would have been a wait so I just opted for the blank ones.

Weighed the car.

2799gs. At the start of the season, the car was 3123gs. So that's now a pretty massive weight loss. It's nearly as light as my small block Mustang car.

The wheels have a different offset than the JC wheels, so I needed to use a pair of 17mm hub extenders, which somehow I already had (no idea why I had them actually). This turned out to be the most perfect size as it provided more clearance from the exhaust header which previously tended to slightly rub the tire when the suspension was compressed. It's a tight, tight fit with the Viper body though, but nothing rubs at all, so I think I'm good to go.

That's a lot of meat filling out those wheel wells

Now I have to fix the Mustang, as it's got the same glitch. However, rather than replacing the chassis, I'm 3D printing out the mounts using a new high impact resin that I found and correcting the toe-in that way.

This resin will allow me to use my own bulkheads now for my chassis design. This stuff is insanely tough, probably more so than the OEM parts actually. It will help me out a lot with production since I had to modify the OEM bulkhead and suspension mounts to deal with the Jato transmission.

 

[johnnydmd]

Finally got around to re-doing the mount on the green body, which makes my wife a lot happier because she loves that one and wants me to use it for racing. Alright then...so I really wanted to use the wing that I made myself, it's just a lot nicer and thus I printed out some struts in high impact resin. Loving that stuff Also put in all the window rivets, which took most of my evening. Need to make the "II" graphic for the hood yet.

 

[ahr43]

Looking good, johnny. Yeah, I learned listening to the lady goes a long way to ensure future funding.

Chassis looks like its packin' a lot of chute. How's that working out?

Don't know if you follow 1:1 drag racing? In the event you do here's a link I stumbled onto yesterday. It's a "run-what-you-brung" series only requirement being 80% nitro in the tank. Some old school chassis showing up there. Wondering how something like this would work out for RC no-prep? Have to adjust the nitro. 35% minimum perhaps? What percentage does your car run? What's the standard these days? 40%? Cheers. 'AC'

Nitro Chaos

 

[johnnydmd]

Looking good, johnny. Yeah, I learned listening to the lady goes a long way to ensure future funding.

Chassis looks like its packin' a lot of chute. How's that working out?

Don't know if you follow 1:1 drag racing? In the event you do here's a link I stumbled onto yesterday. It's a "run-what-you-brung" series only requirement being 80% nitro in the tank. Some old school chassis showing up there. Wondering how something like this would work out for RC no-prep? Have to adjust the nitro. 35% minimum perhaps? What percentage does your car run? What's the standard these days? 40%? Cheers. 'AC'

Nitro Chaos

Thanks!

The chute is a standard 24 inch Estes rocket chute. They have to be modified by cutting it into a cross just like the 1:1 cars, and cutting a hole in the center. Otherwise it'll lift the rear very easily. It's worked quite well. The trick is knowing when to deploy it, definitely not a great idea to do it too soon and better to wait for it to be about 30 feet past the trap and slowing down some first. It has saved my butt a couple of times though.

I haven't heard of that type of racing, not sure how well it would fly with RC nitro since you have to change some things to account for nitro percentage differences. Most guys really have their preferences. I think most racers are using 30 percent, some guys use 50 percent though.

 

[Jaydiaz1993]

More weight loss. Changed out the Vanquish OMF Outlaws for some ultra lightweight alloy wheels and these new tires that ProLine Makes. Lost another 100 grams. Car now feels very noticeably lighter in my hands.

View attachment 163489

Probably notice, maybe not, there is now a gyro in front of the receiver. I am fully aware that many events don't allow them (though I really tend to think that's a silly rule, among other silly rules that I'll not get into on this thread but maybe some other one). It's easily disabled in those instances. Reason I put it there? Why not use all available tech to get the fastest run possible? Now I'm able to turn things up a bit more.

A look at the new front wheels:
View attachment 163490

Also, I tried my hand at carbon fiber stencil painting on the front canards:
View attachment 163491

Kinda cool I think.

Sunday is our next TNT. It's going to be in the upper 70's, so should be able to get some decent hits and data.

I have a Force .38 arriving Friday that is earmarked for one of my MT's, but if I have time and get it broken in Saturday, I might do a few hits with it in this car just to see what it can do. (hopefully not blow up the entire drivetrain).

Wow man, the end result looks amazing.