INVADER - Nitro Slash drag car

[ahr43]

Interesting wing install, johnny. How does it function? Offers more survivability? Wing depresses at speed for less drag without lateral stability sacrifice?

If nothing else, it certainly looks trick. 'AC'

 

[johnnydmd]

Interesting wing install, johnny. How does it function? Offers more survivability? Wing depresses at speed for less drag without lateral stability sacrifice?

If nothing else, it certainly looks trick. 'AC'

I got the idea after looking at some pro-stock Vipers to see what they did, and I saw a few of them that had the wing supports raked back instead of more straight up like a stock track Viper. They looked pretty adjustable, so I thought heck, make this thing adjustable so that's kinda where it started. I have both of my bodies with it in its lowest position to start with for those reasons you mention, less drag, more survivability in a crash for sure. I had visions of having the wing mounted straight up from the deck just ripping right off on a flip on the big end.

I have exactly one full pass on this body with the wing at that position, and it was the best pass my car ever made, so I have left it alone for now. I probably won't change the angle/height unless I experience issues with blowing the tires off after 60 ft (something I did experience when I was using the Vette body, but there were other factors/issues for that as well).

 

[johnnydmd]

Finished it up, other than mounting the blower and mirrors which both still have an epoxy finish curing. Love how it came out, it's not as perfect as the other one I did, so I'll run this one and keep the other as a spare and show-n-shine body. Also it's much easier to paint this scheme, so I might do another couple of them during the offseason to keep as spares.

 

[ahr43]

Outstanding finish, johnnydmd.

Epoxy finish on the blower? Is that for looks or protection? How do you apply it? Always on the lookout for new TT&P. My MT10 Rival has an exposed blower on its hood. If epoxy coating offers additional crash protection, I'd be interested in doing that too.

Anxious now to read how your build performs. Cheers. 'AC'

 

[johnnydmd]

Outstanding finish, johnnydmd.

Epoxy finish on the blower? Is that for looks or protection? How do you apply it? Always on the lookout for new TT&P. My MT10 Rival has an exposed blower on its hood. If epoxy coating offers additional crash protection, I'd be interested in doing that too.

Anxious now to read how your build performs. Cheers. 'AC'

It's for both looks and protection. Makes the surface shiny and smooth, but also protects the paint from nitro fuel. I suppose it would offer some protection for crashes too, but there's a reason I mount these with screws instead of gluing them in

 

[johnnydmd]

Done. Gonna do one more up this way, so I'll have 3 of these in total which should be plenty.

 

[ahr43]

Outfriggenstanding build, johnny. Super detailing makes it look like the real deal. Intimidating too. Set the guy in the other lane off his game from the get-go.

2.50sec Index was my fav class back in the full prep day. Fast enough for good racing, yet slow enough to still drive the car out of trouble. The rail I ran in the 2.50 class was actually built as an electric top alcohol (2S Lipo) 1.90 car. So it settled right into the 2.50 class. ~60-65mph is a good speed too. Bumping right up against the full aero envelope still allows for a fast car build with a lot of detail not to worry about aero drag.

Have fun and let 'er rip. 'AC'

 

[johnnydmd]

Outfriggenstanding build, johnny. Super detailing makes it look like the real deal. Intimidating too. Set the guy in the other lane off his game from the get-go.

2.50sec Index was my fav class back in the full prep day. Fast enough for good racing, yet slow enough to still drive the car out of trouble. The rail I ran in the 2.50 class was actually built as an electric top alcohol (2S Lipo) 1.90 car. So it settled right into the 2.50 class. ~60-65mph is a good speed too. Bumping right up against the full aero envelope still allows for a fast car build with a lot of detail not to worry about aero drag.

Have fun and let 'er rip. 'AC'

Thanks!

I'm itching to run this car. We keep having this mild winter, but the weather on the weekends has been mostly awful, or it gets cold again. I really don't know what it's capable of just yet. It ran 2.3 with the Vette body and the KE25 engine, and Hoosiers on the back, dry tire hit. I was never able to really "let 'er rip", doing that usually wound up in a cartwheel. Then I switched to the Viper body (my slightly larger, heavier homebrewed one), and the SH .28-8 and had one, untimed run that I was kind of "gingerly" on the throttle because I could tell right away there was a LOT more power. Even still, it lifted the front wheels for about 15 feet and really got out of the hole. I also wasn't using the trans-brake due to the lack of data and fearing a spin out.

Now the car is using the lighter and smaller Bitty VPR body, huge Dotek treaded tires and lighter wheels. Car is overall lighter, haven't weighed and balanced it yet, but will this week probably. I ditched the heavy AJC parachute for my own much lighter design. Trying to find the balance between weight and traction, I figure if I need to add weight back that's easier than trying to put the car on a diet. I really like the aerodynamics of the body and how the wheels tightly fit and should keep more air out of the body - that's really the biggest issue with these little cars. Also why I designed that rear window vent system to alleviate air pressure out the rear of the car.

We'll see what this thing does soon, I guess. I've been shooting for sub 2.0 and didn't quite get there last year. My 2.3 dry tire run on the Hoosiers, which aren't really the best gives me a lot of hope. That's a good dry tire time for any car really. I've seen what cars using Doteks can do, and I am thinking that will give me the boost I need to keep the car planted - and then I can really "Let 'er rip"

 

[Riboild-TRX]

@johnnydmd I find the east coast to be just miserable most the time from around octoberish to dang near april. I have been on the east coast since 2008 and I love the Cold, but in essence Nobody else does and you really can't do much short of hunting, watch TV, or for me Play drums and fix the things I broke when it was nice outside!!! Namely for me I just broke out the Traxxas Rustler Nitro that was originally a Traxxas Nitro. I had the same one in the army and stupid me sold it when I got out in 2001 when money was tight. I had a severe amount of money invested in it up to that point and still Hate that I don't have it any more. But at least I learned from that one, and as soon as some funds came around and the itch returned, oh yeah and somebody had an old not too bad shape Nitro Rustler on sale on Fleabay, I Scratched....

I started on page one of this thread that google brought me to in search of a 2 speed tranny and slipper clutch mod for my Rustler nitro. I can say this, you and I have a lot in common as far as our likes and, at least from my POV, attention to detail, and desire to do things even if we have to make it or fix it ourselves. I am stunned at how much you have done and wish I had room in the basement for an actual 4x8 CNC router as I spent a lot of my time as a CNC Machinist and fabricator. It would have gotten me in trouble a long time ago though as I would have always found a reason to use it, even if it wasn't for a customer... LOL... Keep up the great work btw and I am fully involved when you update some more!!!

 

[ahr43]

Welcome to the forum. Looking forward to a project thread on your nitro Rustler. Cheers, mate. 'AC'

 

[johnnydmd]

Warm day Sunday - figured it was time to break out the Invader II and see how the new ceramic bearings felt and get the car tweaked. As it was, I didn't have to touch a needle, or linkage, or nothin'

Also a few graphic updates on the body - printed out some new grill/vent stickers, kinda gave it a "Tron" look in the front.

Weather is supposed to be all over the place the next couple of weeks. Planning on going to Rockingham in two weeks though if the weather holds up for a test 'n tune and meet some of the big players in the nitro drag racing scene.

 

[ahr43]

Looking good. She's a-rockin and a rollin on the test stand. Locked and loaded for shake down runs.

Rockingham. Ran an RC drag race national there 2008. Liked the set-up. Had an uphill slope for shut down runout. Really helpful after a hard run. Wonder if they still use the same course layout? Anyway, have fun at "The Rock". Post up some vids if you take any. Cheers and good luck. 'AC'

 

[johnnydmd]

Looking good. She's a-rockin and a rollin on the test stand. Locked and loaded for shake down runs.

Rockingham. Ran an RC drag race national there 2008. Liked the set-up. Had an uphill slope for shut down runout. Really helpful after a hard run. Wonder if they still use the same course layout? Anyway, have fun at "The Rock". Post up some vids if you take any. Cheers and good luck. 'AC'

I believe it's the same course, and that's a real similar layout to the one we have in Annapolis with the up hill shutdown. Really love that.

 

[johnnydmd]

TnT this past Sunday as noted on another thread. It was 60, sunny, but very windy. We limited to 66 ft hits, without bodies. Nobody willing to chance a full run, or with a body with 20-25 mph winds.

The Doteks were awesome! I was amazed at how hard the car launched and stayed hooked up. We didn't set the timers up because I didn't have the right connectors to do at 66 ft length, but we did use the tree. I made 3 or 4 passes with this car. I would have made more but I need to get back into the lab beforehand. For starters, the car keeps the wheels up the entire 66 ft. Not kidding about that. Two of my passes the car started drifting and I tried to correct it but that's impossible when the front wheels aren't touching! I was also having some issues with steering alignment, which has prompted me to finally order a setup station. I was able to sort that, but it took time from my day. I also was chasing a very narrow tuning window. So more time got spent on that. My final pass though...wow. It was wheels up but stayed straight (another testament to those Doteks!). I don't have an official time on it but it was easily the fastest, hardest launch I've made, or even seen made by any nitro SE car. Even the brushless guys that were there with us jaws dropped. That pass would have been well under 2 seconds in 132 ft.

I'm sold on Doteks. I've used Reactions, Hoosiers, foams with prep on this road. Nothing even comes close to what the Doteks can do on a rough road like this. I'm also convinced that with this big block car, wide meats are the best meats. With that in mind, I did order some Mambos for running on smoother surfaces, because on a smooth track, I think the Doteks won't do as well as a slick. The dimensions are identical, and I got the blue compound, which is the all-around compound.

I was really impressed with the tackiness of the blue Mambos, even before rubbing them down with WD-40. I will test these along with the Doteks side by side to see which one works better on various surfaces.

 

[ahr43]

Good follow-up test article, Johnny. Reads like you're well on the way to gettin' her dialed.

Interesting comments on running body off in the gusty wind condition-as well as limiting the run distance. Good solution to getting runs in under adverse conditions. We ran some 66ft events back '10-'11 or so if we didn't have length enough for a full132ft course and shut-down. Don't recall any issues with timing set up. But then, I was just a racer, not involved in set up or timing.

Have experienced similar adverse weather circumstances on speed runs with the Rusty here. Did the limited distance thing, but running body-off did not occur to me. Keeping that in mind as an option for the next windy day trials. My front air dam attaches to the chassis, not the body. So will still have that to defeat lift-to-kite tendency.

Cheers and best of luck in the upcoming season. Looking forward to the first race report. 'AC'

 

[johnnydmd]

Thanks!

The timing issue was due to the cables - it's divided into 3 sections (2 50 foot and one 32 foot). We needed a 16 ft extension to make it work with one of the 50-foot pieces, because the cable is inside of flat coverings, wasn't able to ball it up or put it anywhere out of the way very easily. I guess we could run it back past the tree and looped it back though.

 

[johnnydmd]

Weather has gone back to sucksville for the foreseable future in these parts. Decided to do some upgrades, functionally and cosmetically.

First, I really wanted to paint the window bolts/rivets in the Viper body, but unlike the Vette, they don't have them molded, so it really would look kinda iffy I think. So I thought, why not just actually put some bolts in? I had a bunch of 2mm cap head bolts, and they don't weigh anything. So I marked them up, drilled, and put in a bunch. Should do it to the Vette bodies too

Now that's got more of a real race car look. Took one more beauty shot before this body gets scuffed up from action.

Under the hood, I'm doing some things. My throttle servo is a high speed AGFRC coreless that I have slowed down on my radio. I can only slow it down so much there. With the KE25 I had it as slow as I could at first and used a concave throttle curve to gradually bring the throttle up over about, 30ft or so in most runs. I decided it would be a better move to go to a slow, high torque, *programmable* servo, like this:

The servo arrived, and I hooked it up, and saw that I could take it down to a craw. The programming module hasn't yet arrived, but I can take it down even slower with that, and there's a bunch of parameters I can tweak on it, using a laptop. Now I can use the throttle curve on the radio to mess with the curve a lot more effectively over the first 60 ft or more. I can have it launch hard, and then slowly move to wide open, or launch soft, and have it open faster after it gets moving. Will be a lot of fun to try out different tunes...and be like Ryan Martin with my laptop hooked up to my race car

I also wanted to do something different for the front body support. I smashed them on both cars in last week's testing. I thought about buying the Exotek front bumper but wasn't sure if it would work to hold up the nose. I designed something similar.

Just hand cut the CF, I'll make something prettier for my router. However, it works - but here's the difference. Instead of having foam mounted on the CF plate, I filled the front of the body with foam that rests on the plate. That way I have 100% full contact and support inside the body, and can switch to different bodies if needed.

Did this for my Mustang as well. This will work very well, I think.

 

[Doom!]

Really like the window rivets! the little things can mage such a huge difference. I love little details.

 

[johnnydmd]

I've since removed the fuel line cooler, that little thing is pretty heavy and the more I think about it, it serves zero purpose for a drag car that isn't really getting that hot to begin with. In fact, I've ordered and engine heater, as it's just too hard to get the engine to temp quick enough - though I may also use a cut down head as well. Did a little weight check:

Shaved off about 100 grams of weight since end of last season. Not huge amount, but I was a little worried about it getting too heavy. Lighter chute system is a big help. Balance is still really good on this car. 6.6 lbs overall. Pretty heavy. The Mustang is 5.4, the Nova 4.8 lbs. Of course this car has nearly double the power of the Mustang, and more than double the power of the Nova.

Did a little testing Sunday, it was 54 degrees and a bit breezy. Not a good traction day. I was able to at least do some launch testing and programming of the servo to see what I could do on some very "A to B" full passes.

While the temps weren't great to see what the car could do in terms of how fast I could get it, it gave me a chance to play around with the parameters. I slowed the servo speed way down, could have gone slower, but took it down to around 1 second or so for it to fully open the throttle. Then I cranked up the damping factor to 600. What this did is slow down the top end of the throttle, so it gets to about 3/4 open, maybe less, and very gradually goes to full. I made a few passes, also with "Soft start". It was A to B, though pretty slow, I was able to mash the throttle from the get-go. But it made it on bad traction, so that's a start. I wanted to push the launch a little harder, so on the radio I changed the throttle curve from near linear to very convex at the start. That definitely made a difference on the launch. So now I have four or five factors/tuning points to work with and can pretty much fully control the throttle arc through the entire run. Throttle speed is of course going to be the one factor that can get pushed in better traction. Damping factor can be really useful for when I'm having issues at 50-60 feet of it blowing the tires off in the power band, by keeping it from going full throttle until a little later. Harder launches by disabling soft start and ramping up the throttle curve at the beginning.

Definitely building a spreadsheet.

 

[johnnydmd]

Had an extra cooling head and been meaning to do this for a while. Cut the head down to two fins. This knocks off another 61gs, and will make it a heck of a lot easier to get the engine up to temp. Lots of drag racers do this for that reason. Car now down to 6.5 lbs. Will keep the spare head for those 90+ days where I might need it.

I believe (without going back through this thread) that the car when first built weighed 6.8 lbs with the small block, Slash trans setup. So now the car is 1/3 lb lighter, and nearly double the power from it's 2019-2021 incarnation.

There are two areas where I can fool with weight without removing any functionality (such as trans brake or chute). Both front and rear suspensions, body posts, and bulkheads are alloy. I could replace portions of this to decrease weight if I wanted to, and probably get the thing down to under 6 lbs. The links look heavy, but they are lighter than stock ones (and way easier to tune).

However, I don't think I want to shave any more weight off at this time. I'm still keeping in mind the 60 ft pass I made a couple of weeks ago. I need to see what this thing will do on a full pass with this configuration.