INVADER - Nitro Slash drag car

[Doom!]

So now that you've got that chute you can launch it off the roof right? I think this is the most badass RC I've seen, inside and out. At this point I don't know how it could get any cooler but you keep surprising me.

 

[johnnydmd]

So now that you've got that chute you can launch it off the roof right? I think this is the most badass RC I've seen, inside and out. At this point I don't know how it could get any cooler but you keep surprising me.

Thanks, that's mighty high praise! There's still a chance half of these mods fall on their face when I get to testing, lol.

 

[WickedFog]

So now that you've got that chute you can launch it off the roof right? I think this is the most badass RC I've seen, inside and out. At this point I don't know how it could get any cooler but you keep surprising me.

I dunno, his Demonoid monster trucks are pretty epic. I would say Johnny has some of the coolest RC builds I have ever seen. This one is way up there, but the monster trucks and that crazy Mars Attacks martian car are just phenominal builds.

 

[johnnydmd]

I dunno, his Demonoid monster trucks are pretty epic. I would say Johnny has some of the coolest RC builds I have ever seen. This one is way up there, but the monster trucks and that crazy Mars attacks martian car are just phenominal builds.

Wow thanks man!

The Mars Attacks themed body (original Invader body) I no longer have in possession. I had given it a couple of test runs a few years ago, and the car was squirrelly, and slow. That body weighed a bit extra with the 3D printed martian and engine too. A friend was over and really liked it, so I gave it to him and he stuck it on a DR10, but we've lost touch for reasons, and I think he painted the thing black or something.

 

[johnnydmd]

Designed this during lunch today - a bracket that mounts on the front of the Slash bulkhead (where the front bumper would normally bolt up that serves as a way to mount the GNSS module as well as provide body support for Corvette bodies(and really could on other ones too). The support piece will have a piece of foam glued on for the body to rest on, and it's adjustable. This will keep the body from bending down at high speed, which is an issue for any fast car using the stock body mounts, but especially for one like mine that's got a splitter on the front.

 

[justinjustme]

So glad I found this form and your build. A friend of mine passed away and his girl gave me his rustler which I got running and ran the 25 until it was toast so I upgraded to the 33 and immediately burnt spur gear then I fried a break then I tried to clutch and then I fried the new clutch spring which led me to this because I've been looking for a way to put a two-speed training on it which led me to the jato and now a transbrake idea from you I had seen the parachute but I hadn't thought I'd be that far yet I do have it when I think is okay set a wheelie bars on but I'm tired of eating plastic parts so it's time to go metal and I really think I want the two speed jato I just spent two hours reading your hole build and everything else I had read before about Nitro drag racing with 10 years ago I really hope that there's no prep scene figures out a way to let us in with them too otherwise just be running on my phone all the time as far as I'm concerned it's they're not drag racing no tuning no smell of nitro but it seems to be the way the world is going until then no I'm running Nitro and as cheap as a rustler is I think it's a great platform to build from wish they had a slash lcg for Nitro where I wish I had the tools you got to make my own parts can't wait to see it actually launch I'll be following you good work

 

[johnnydmd]

Well this little bracket was *real* close, but no cigar. The adjustable piece simply sticks out too far, and was also a bit narrow - needs to be wide enough to stabilize the front - so I've redesigned it, so that it should fit perfectly against the raised cowl section. I removed the adjuster, since you're going to need to put foam on the end with servo tape or glue to cushion anyway, it's easy enough to cut the foam to fit.

The GNSS fits perfectly in this, very snug. There's a slot so that you can use a velcro cable tie to hold it down.

 

[Doom!]

Trial and error is what it's all about sometimes.

 

[johnnydmd]

Well, the new design worked flawlessly. The only thing missing is that it really needs a bump stop in the front of the GNSS cage to keep it from sliding forward (for this printed one I'll just put in a screw or something).

Looks like we're going to break the 50 degree barrier saturday! My steel transmissions gears arrive today, so I'll rebuild my trans and hopefully get a few test hits and finally see what all these changes bring.

 

[Doom!]

Hope you get to try her out!

 

[johnnydmd]

Hope you get to try her out!

The gears didn't arrive till Monday Saturday was nice, but I decided without the steel gears it was a better idea to forgo any RC stuff and go out on a date with the wife

I started on the transmission rebuild Sunday (teardown phase), and got it finished last night. It wasn't nearly as easy as it should have been - and now I kinda know why the transmission case wound up on eBay. Remember, when I first got it I wanted to replace the m3 bolts and found that they were red-loctited in, and had to do a lot of work to get them out. I strangely didn't really disassemble everything or really inspect it too closely other than to see that the gears were intact and they moved freely. I probably should have looked closer...more on that in a moment.

So I got started. Aside from replacing the gears to steel, I also wanted to replace all the bearings with Fast Eddy ceramics.

After pulling the gears out, I saw that this thing was in pretty bad shape. There were metal shavings everywhere, and one of the bearings was mutilated and looked almost fused to the case.

You can also see where the two-speed clutch had been grinding against the case due to the bad bearing. This was the likely source of the metal shavings. My homemade bearing removal tool got all the bearings out where there weren't access holes to push them out, except that bad one. Oh man, I struggled and struggled. Eventually the center race popped out, leaving the outer still fused to the case. Eventually I realized I had little choice but to drill out an access hole (really, no big deal, since everywhere a shaft comes out of the case they have them anyway). Given the rarity of this piece, I was pretty scared to do it, but I did, and was able to (very) forcefully get the outer race free, also after soaking the thing in WD-40 for an hour.

The clutch was scuffed, but otherwise it was ok. That's good, because I didn't have a spare, other than one that's in another, complete transmission for another (future) car. You can see where the plastic bump-stop for the clutch is compromised, and was going to fail - a common failure point for these transmissions (and most others that employ similar technique, such as Kyosho Mad series vehicles). Why any of these are ever plastic is a mystery to me!

The Hot Racing gears are well done - well, let's hope that the steel was properly hardened in China, where they are made. My experience with Chinese made gears (on a power winch) is dubious (had them explode into bits). I haven't seen anyone complain about these and many swear by them, so I'll assume they're good.

I put it all together, light coat of silicone grease on the gears (you don't fill them with oil, these 2 speeds have a one-way in them).

Here you can see my access hole in the center. The transmission is still perfectly sealed with that, as the bearing is sealed, and the shaft is in the bearing just like the shafts that go outside of the case.

So now my entire drivetrain is steel/alloy. Meaning, there's no longer a set failure point, which isn't exactly ideal either. Plastic spur is a popular choice, but I have an upgraded slipper clutch that will be utilized properly and (should) reduce any chance of something giving out.

I bought two sets of those gears. They had popped up on eBay, and I grabbed them. There were quite a bit for sale, and they are all gone, only took a day for that to happen. Lots of drag racers snapping them up - which tells you something that's going on in the no prep scene right now with nitro.

The weather is breaking here, at least for a week, so I am hopeful for actual testing soon.

 

[johnnydmd]

Finally - some TESTING

We had a 60 degree day yesterday (sadly, today it's 60, but raining). I got the car fired up, and started working on the tune. Took a while to get things right, now that it's using the tiny little 2.5 oz tank instead of the massive tank in a Mad Crusher. Once I had that running decently, I tested the trans brake. It had NO chance to hold that big block. I anticipated that though, and designed a brake adaptor that would allow me to set up a dual disc system.

Since it's a good bit longer than the stock adapter, it needs to be held in in another way besides an e-clip. The one that HR sells uses a (very, very) tiny set screw. IMO, that's no bueno. I added little tabs that use the disc itself to keep it in place.

This worked perfectly, and I had dual brakes! Wow did they have a lot more stopping power.

I have two pad types - the CF pad I put on the inside, as it worked better with those tabs. The other disc is a little sloppier and I was worried it might somehow allow the adaptor to squeeze through, though probably not, but I wanted to be sure. Nothing worse that losing brakes at 80 mph! You can also see that I have the aluminum (hard to find) brake lever. This is a *must* upgrade, as the plastic one notoriously flexes.

Gave the trans brake a test, and it was perfect. It held with a solid 12% idle bump, which seemed pretty close to the way a 1:1 drag car does - didn't see any flames coming out of the exhaust like a 1:1 though (lol). Gave it a test 60 ft run, and oh my lord. That thing shot out like a rocket, wheels up, on the bar, until I let off. Did a couple more because it was just so much fun! Then I notice my brakes weren't functioning. The bolts holding the pad had backed out (I had doused them liberally with Loctite the night before, but clearly it wasn't working well). Luckily I had thread tape in my truck toolbox, so I wrapped the bolts up, and put them in, re-adjusted, and did some more 60 ft tests. I also popped the chute out, and it worked perfectly. Didn't seem to lift the car any, so I think I have it set correctly. I'll have to work up to seeing how that works on a full test. As it was, I didn't want to run any 120 ft tests this day, I didn't fully trust a lot of stuff yet. I did notice that it was shifting into second pretty early, so at the advice of a friend, I set the shift point as far out as it could, but I might actually move it back some as that seemed a little too much, it was winding pretty high in first.

I did a few more launch tests, just mesmerized by how this thing just leaps off the line. Then the car wouldn't move. Rut row. I had visions of my previous transmission detonating the gears and snapping the shafts. Sure enough, it all seemed to be bound up. Closer inspection revealed that the brake discs were jammed against the bolts, and that the adapter I printed was trashed.

Instantly I realized that I had printed this out hollow. Doh! I really thought I had the infill at 100%, but when I got home, I saw it was 25%. Whoops. Looks like slamming on the brakes at 40 mph was enough to crush it. In reality though, with these powerful brakes, it probably saved my transmission. Bringing it to a dead stop from 20k or more rpm, I'm starting to think *that* is what demolished my transmission the last time. Phew - glad I figured that out before trashing another one. Meanwhile, I printed out a handful more of them, but solid. I also re-programmed my brake rates and curve so that it won't lock up when hitting them (I think my instinct is to always just slam them).

I went back out, tested another dozen or so 60ft launches, did a little more tuning, and tweaked some settings on the brakes, got it where it felt good to hit hard, and a more gradual slowdown without locking up. The KE25 definitely was a big power increase over the OS .21 tm, and I will work on the launches and shift point some more if the weather is good this week, and then I'll start on the full 132 foot passes. Sorry, I didn't take video - I always find that to be a chore, but I'll get some soon, and some data to post.

I also found time this weekend to make some travel cases for my cars out of old military ammo boxes.

 

[WickedFog]

Awesome man. Really looking forward to a vid of this running.

 

[Doom!]

Nice work on the brake adapter design. You really do need to work on getting the flames shooting out of the exhaust though!

 

[johnnydmd]

I really despise this time of year. Weather cannot make up it's mind. It was supposed to be mid 50's on sunday. Nope, hit about 45, and the wind was blasting 15-25. Didn't care. I was determined to test again. Good news - the brake adapter held up just fine. Bad news - I had to chase my hat, and the car body across the parking lot several times. Way to windy to run with the body on for sure. Somehow the wind sucked it right out of the box I had it laying in, lol. Luckily, no damage to the body that I couldn't buff out. More bad news - the radio was losing it's signal at 150 ft. The alloy box has a plug that can be unscrewed, I guess that is for wireless antennae, but not sure. It seemed to help a little to do that. Not enough though. There's something going on with that parking lot and causing me to lose signal there. I took it home, and sat it down on one end of a soccer field, walked to the other. Got to around 250 ft before it lost signal. Still no good. Well, off with the radio box. Kinda knew I was going to have to do that. Sure enough, without the box, I had a good signal even at the other end of the field, 300 or so feet, which is plenty for drag racing.

Meanwhile, before all that radio testing, I managed to do a couple of hits and get video. I was trying to also get some 66ft data, but lord the traction was just horrible. Was like running the car on ice. Just too cold, too dirty, and not the best surface. This video at least shows the trans brake working as intended. Noticing it shifted into 2nd gear at 10ft out, but I will have to wait to test in better conditions to even begin adjusting the shift point. I had the slipper fairly loose - 3/4 of a turn out, but it didn't help, I was knocking the tires off regardless. It was just impossible to make even a 66ft pass on this day.

 

[WickedFog]

Holy crap that trans brake works great man!

 

[Doom!]

Sucks nothing was going your way. I've got two planes that are waiting for their maiden flights but the wind is not cooperating so I understand your frustration.

 

[johnnydmd]

Holy crap that trans brake works great man!

Thanks! That was an 11% idle bump, it could surely hold more. I could also upgrade the clutch to a Buku adjustable and toy around with some really high spool ups, and maybe use the slipper to reduce traction loss.

 

[johnnydmd]

Did more testing, similar issues on a similar surface. My day got cut short because of rain. I got to run about five or six 66ft passes, a couple of them were really good, but the final one I spun out at the end and cartwheeled. No major damage, just some minor road rash on the body that buffed out fine. On the plus side, I saw a surface one parking lot away that was super good, but didn't realize it until I was leaving. Met another racer who was on that lot too.
I really dialed down the throttle, was at 30%, slow speed, but steep rate at the start. I was under 1.5 seconds on a couple of the passes at 1.5g's and over 40mph. I really wanted to play around more with this, dang rain. I got my shift point a little further out, but it could still go more. On the last pass, it was on the wheelie bar all the way through first gear, and stayed straight. When it hit second, it lifted again, then the left tire broke loose badly, causing the car to veer very hard left and cartwheel. It may have been dirt/dust on the road.

One thing for sure - the Kyosho KE25 is more than enough engine. I have way more power than I can get down. A few other racers building similar cars are telling me the same - that big block drag Slashes/Jatos are really, really hard to get A to B, lot of tuning involved. I have heard the KE25 is a top ender, so we'll see once I do a full 132 ft pass.

With the limited data I have, and poor traction at that, I have zero doubt that I can get this down 132ft in under 2s. Once I get the 66ft under 1.5 and where I can trust it to not spin out at 60 or 70 mph, I'll feel more confident in letting it rip the 132.

 

[WickedFog]

I was looking at our lot the other day and noticed little pepples, differences in height of the concrete slabs, etc, and thinking to myself that any of those little things would wreak havoc on a good run. I bet that is what happened to your run. Some tiny little thing, or like you said, dust. If your engine has a lot of top end, that may explain it too.

I am looking at getting the Maclan ESC for ours, just to try to get good launches out of it. But that is still a couple months out.