My Latest RC Addiction: Speed (Infraction)

[morrisey0]

I traded my built DR-10 for an Infraction. TBH, $$$ wise it was a pretty square deal; both having close to about the same in each, but I feel like I got the much better end of the deal! These big Arrmas are just impressive!

I have decided this is just going to be a straight up speed rig. No bashing, no drifting, just speed times. I am also currently only interested in keeping it 6S max. So the ultimate goal is how fast can I get it on 6S.

I finally got a small opening today of not having too much to do and it not raining. Prior, I have only run it up and down my street, which is just not enough room to get it going. I found a pretty straight and rarely used road (on weekends), and went testing for a baseline. Unfortunately, I made quite a few runs in the parking lot prior to getting it out on the road, and it kept knocking out after about 100' or so once I had the space to open it up. I am pretty sure the ESC was cutting out on temp. I saw 69mph in the parking lot, and it was noticeably faster on the road, but my SkyRC had fallen out by then (just had it shoved in there). The interwebs is filled with 85-95mph first runs on speed gears, so I am just going to run with something in that range as a baseline. If I get another chance to run with the current setup prior to the new ESC coming in, I will try again.

Future plans: CC MMX8S ESC, dual fans on stock motor, Limitless spool, design and print ESC and SkyRC mount(s), print temperature monitoring station, and start saving for tires because OMG they go quick.

As she sits all pretty:

Next to my 10L for size comparison:

My only time slip for the day:

First mock up of the temperature monitoring station. Hope to have a probe directly on motor and ESC, but haven't figured out that part out yet.

[shodog]

An Arrma Felony is on my short list of vehicles to get. I like that the infraction has the center diff brake. I’ll probably put that on the Felony

[morrisey0]

Had a little time this evening, so got a couple of things started.

New motor heat sink with twin fans mounted. Temp probe squeezed in there nicely. Need to finish the wiring. Found one of the motor mount screws stripped and no set screw installed on the pinion gear. POs are the worst!!

Found an easy GPS mount stl online and got it in. It seems a little weak at the mounting tabs, but maybe it is good enough.

But the biggest change of the day is the shoes! The guys at the LHS are all about the GRPs, and I got to thinking that maybe the yellow/green would work with the silver, and dog gone it, I think it looks BA!!

[R6cowboy]

Dig the new wheels, they look good. I haven't done anything to my Typhon except for Proline badlands. Got 56mph on the Skyrc with the stock small pinion and two 5400mah 3s batteries. Would like to see what it can do with the speed gear but need on-road tires first and add thicker diff fluid.

[XLR8]

I agree, the new wheels look great.
Yellow wheels just seem to work with just about any color scheme - not sure why but they do.
Anyway, I had my 6s animal out last evening - what a hoot!!

[morrisey0]

Todays updates:

Got the MMX 8S ESC in, and made a mount for it. I 'lifted" it out of the cavity the stock one fit into, maybe thinking it would allow a little more airflow / cooling. Might to nothing, but might.

I had gathered all the parts I thought I needed to quickly slap in a "limitless" spool, but after pulling the stock Infraction diff, there are obvious differences. Apparently the entire gear range is different between the two as the Infraction comes stock with a 46t spur, and the limitless comes with something in the 28-34t range. I have put in the order for a 46t 8mm bore mod1 gear, which from what I can find, one company makes. Also found out that the "handbrake" disc is driven off the rear drive cup, so that needs to be ground down to keep the brake.

I am in the process of printing what I hope will be my main switch box for the whole rig. I am planning on running a mini 3P switch to control: 1) esc power, 2) power to motor fans off one battery, 3) power to temp monitors off one battery. That way I don't need to remember (and probably forget) to plug things in all the time. The batteries are either plugged in their chargers and balance plugs, or they are plugged into the esc and accessories. On run day, one switch is on or off.

[Frankentruck]

I just imagine how much carnage there would be to the vehicle and whatever it might hit if something goes wrong at those speeds. I wouldn't have the good sense to have the appropriate when & where to go that fast and stay in control. I think I need to look up some videos of things gone wrong. It would probably look just like a NASCAR with everything flying apart on impact. It is a sweet looking runner though.

[morrisey0]

I just imagine how much carnage there would be to the vehicle and whatever it might hit if something goes wrong at those speeds. I wouldn't have the good sense to have the appropriate when & where to go that fast and stay in control. I think I need to look up some videos of things gone wrong. It would probably look just like a NASCAR with everything flying apart on impact. It is a sweet looking runner though.

Completely legit concern, and one I am working with. My honest fear when driving this wide open is, what is a cat or dog jumps out in the road? This is 13lbs at 80+mph! It is like a 1 in 1mil chance, but I think about it.

The amount of room needed to run a rig like this is long, and much longer than I anticipated. I have found a 1500' (.28 mile) stretch of 2-lane road usually not used on the weekends, and to be honest, I use every bit of it and could use more. To speed run these things and not destroy the tires is like running Bonneville. A bit of time to spool up, make the run, and A LOT of time to spool down. You don't realize that the the 90-to-0 line is much longer than the 0-to-90 line. My Infraction has a "handbrake" which is a rear driveshaft brake, but right now it is on or off, and right now it is rear tires roll or rear tires lock. My spool will neutralize this a bit, and hopefully I can get it adjusted so that it just produces enough friction to slow the vehicle down without locking up tires, bit it is a little 1.5" rotor trying to slow down a 13lb car going very fast. I would love to find a parking lot of such length, but lots are surrounded by curbs, and yea, curbs scare me. I have gone into the ditch on a few occasions at speeds that a curb would have destroyed the rig.

As far as control, the stock Spektrum AVC has been spectacular so far. Point and shoot. You aren't making constant corrections; the RX is doing it for you. I am planning on swapping this over to my RadioLink set up soon to keep all my cars standard, and the RL does have its version of AVC on the RX, and I really hope it works as well. Time will tell on that one. If I can't get it adjusted to perform as well as the Spektrum, I will swap back.

I was hoping to complete my "Phase 1" mods this weekend and get a couple of runs in, but two different bad gear shipments have made it so that I shouldn't be able to get my spool installed, and if I stick with my stock diff, I won't have any taller gear ratio to run beyond stock "speed" gear (25/46). Also, the road that I use to run on, that I stated isn't usually used on the weekends, is actually the main road to the county fair ............ and guess what starts this weekend?

[Frankentruck]

I remember seeing a baseball pitcher hit a bird with a fastball. Poof went the bird.

I know it's in the category of 'bad ideas', but if that thing had deployable glider wings, if would easily take flight at top speed.

Do they make drag chutes for them?

[morrisey0]

Well, I am on hold waiting on gears at this point!

I did go through and get 90% of the wiring done, and it came out pretty clean. One single loom along the spine keeps it all in check. The only part left is the temp monitor on the bed, but that will just plug in. Single switch in the front turns on fans, temp monitors, and esc.

At some point in my life, before I die, the lesson that "cheap parts cost you more in the end" is going to sink in, I don't don't know when! As shown in a pic above, I am changing over from a traditional differential to a straight spool, as this rig is being built to just go straight. The spool set up is built from several individual parts, of which of course Arrma makes, and "others" like HR make. I made a mistake by saving about 25% by going with HR shaft and input cups. At this point, I think the shaft is the issue, but I am not 100%. I have an Arrma shaft on order.

I just happened to throw the setup on the mount and spin it over, and noticed the obvious issue. It kept stopping at the same point, as if there was an out-of-balance issue, or a bent issue. I could have easily just put this thing together, and ran this spool at 10K+ RPM. I really can't imagine what would have happened at that point.

How do you make something this crappy?

Note how one side of the cup collar is flush, and the other is 1+mm out!

[juicedcoupe]

Do they make drag chutes for them?

[morrisey0]

Just updating this really just for my own good. This thing continues to intrigue me and frighten me at the same time, which I why I think I continue to move forward with it.

Have a set of 25/42 gears in there with the stock 2050kv motor, and could finally record a 90+mph run on 6s. My motor temp sensor never went higher than 141*F. It will do more than this, but my main issue is finding the real estate to let it loose on.

I thought I found a great road this weekend, until I found "the hump" on the second run. After that, the truck was like a moth to the flame and couldn't avoid it!

Quick vid. 1st pass, okay. 2nd pass, hello hump. 3rd pass, why am I on this road? 4th pass, I should have just hit the hump. 5th pass, I thought the other way would work, but then hit the hump MUCH more violently off camera (listen for it).


But ultimately, a recorded 91mph is a recorded 91mph. Next phase is more gear and less drag.

[R6cowboy]

Off camera background noise on the 5th run sounded gnarly. Any damage report? Congrats on the 90+ run.

[morrisey0]

The last roll was bad, maybe 6-7 flips for 30'+, but no real damage. These things really are built like tanks. Weight was not a concern when designing these, as Arrma felt you can power up through weight, and it shows because these things are heavy and built solid. I actually wasn't shocked when I picked this up with no real damage. The body had actually flexed enough to push down on my main power switch and shut the whole thing down ................... which of course was a safety device built into my design.

I do love and hate the body. But my goal right now is to build speed, so form can't be a concern, so the block like body must go. I found something a little more aerodynamic. I don't hate this form either.

Problem is that I am probably going to paint it more functional than fashionable, which I haven't figured out yet. It is going to be bright and obvious, but not blend into the road 300' away on a sunny day. I need a paint job that says, "I am here and pointed this direction!" Who knows.

[morrisey0]

I have made some changes over the past couple of weeks.

The most drastic is the body, but that isn't complete at this point, and the next three weeks are going to be "no rc time" so it isn't going to change for now.

BUT, because of the body change, all of the custom parts that I built to fit the truck are a no-go, so a complete re-wiring of the ESC, motor fans, and temp sensors had to be done. I am happy with it overall. What is nice is the power switch is on-off-on, which I just had as double-throw previously, but now one on is fans and sensors, and the other on is fans, sensors, and ESC. Keeps me from having to power up the whole rig to run motor fans for cooling down.

I did put a new CC 2200kv sensored motor in it. The jump from 2050 to 2200 is only 7% (and I shouldn't sell that short), but sensored helps a lot with tuning. Matching the ESC to the Sensored motor is an added bene. I am also going to start bringing along a separate tablet to BluTooth to the CC system, and I can keep my phone BluTooth on the SkyRC.

New P/S ratio is 27:42. This, with the change in motor, should be over 100mph. I was seeing about 10-12*F temp rise during every run previously, so there is room for upping speed there. I am also currently designing a pit / cooling box, that will throw ice-cooled air under the body during cool down times to lower "under-body / ambient" temps. I am seeing under body temps in the 110-115*F range, so if I can drop that closer to actual ambient temps, that will greatly help with reducing motor / ESC temps. But seeing in that it may be November+ before really getting running again, I may not prioritize this.

New chassis overall:

The new body overall. Honestly, just 2sexy! I wish the front was a little more aero, but when compared to the Infraction truck body, it is night and day!

New rear sensor mount and power switch:

The temp sensors are now mounted so they can be viewed through the "mid engine" clear opening of the body: