Wraith trans choices for sand/dunes

[TheLetterJ]

I'm still acquiring the last few parts for my Wraith sand toy/Foff build and can't seem to make up my mind on the transmission. I've read through dozens of Foff build threads, and all of the wraith stickies, but I'm still torn. My powertrain consists of a Hobbywing 120amp sensored esc, 3400kv (3656 sized) 4pole sensored motor, 14/54 pinion/spur, standard ratio HD front R&P, HD UD rear R&P, and 2.8 sand paws. I'm currently planning to run my existing 3s packs, but 4s isn't out of the question in the future. I have other dedicated crawlers and go-fast RC's, this one is being built with dunes/sand in mind

I'm sure I'll be playing with the spur/pinion gearing, but I want to beef up the trans before the maiden voyage. I'm kicking around a few options and would like to hear some opinions:

1) Hot Racing cases with either SSD or HR gear set (2.6:1)

2) SSD high ratio kit (1.8:1)

3) SSD 2 speed (1.8:1 and 4.9:1)

4) just throw some HD gears in the stock cases (2.6:1)

Option #1 seems to be pretty tried and true.

Would #2 be a better option given my intended use? Cost is about the same as #1 and it would give me a nice bump in wheel speed, greater than switching to 4s. Not many people seem to run this trans, but it came out after most of the builds I've been reading. This is the option I've been favoring.

I hadn't really been considering the 2 speed until recently, but it does have the same high gear as the high ratio kit, and an uber low gear (allowing me to turn it into somewhat of a "crawler" along with a quick tire change?) for not much more money than the other options. The 2 speed would allow me to gear on the tall side for open dune running without giving up anything on the low end... or is that a moot point with my sensored brushless? I'm not really a fan of adding more moving parts if #1 or #2 are BETTER options.

#4 is cheap, but I have my doubts about the plastic housing living very long so I think I should probably skip this option?

Thoughts?

[TheLetterJ]

After playing around with this calculator: R/C Calculations I think I've got a plan. With the SSD high ratio kit and my current setup, I've got a theoretical top speed between 25-29mph (UD and standard gears, so somewhere in between.) If I drop just 1 tooth on the pinion, I think it will be plenty fast enough, and not be totally useless on more technical climbs. That would be closer to the speed of stock tranny gearing on 4s, but without the added drivetrain stress, and I won't have to buy more batteries.

[TheLetterJ]

Anyone here run the SSD high ratio transmission in their Foff rig? Is the drive pin on the output shaft (the one that the gear rides on) going to cause headaches? That is really the only potential negative I'm seeing, but I'd like to know if it's even an issue?

[TheLetterJ]

Well being that this has been a one way conversation, I might as well keep talking to myself! I'm almost ready for the maiden voyage, I just need to finalize my esc mounting and tidy up the wiring. I did run the car on my lawn last night and I was a bit underwhelmed by the acceleration, hopefully it grabs and goes better in the sand. I'd estimate actual top speed at just over 20mph, so I'll bring some bigger pinions with me when I take it to the beach... I can see 4s in this car's future.

Purdy transmission:




Getting closer:

[TheLetterJ]

I'm thinking it's pretty safe to say that the Axial 1.04lb springs are too soft for my setup. It sits at more than 50% compressed at ride height (2 1/4" under the skid.)

I think that I'd also like to go with Dlux's U4 truss that mounts the servo behind the front axle, both for housing strength, and better bump clearance. I already have SS beeftubes in the front, but I threw the rear axle truss on the bottom of the front housing just for kicks, I think it looks good, but I'm sure it will be a plow.



I love the way the SSD centered D60HD looks under here:



Profile view showing the ever so slightly stink bug stance, which I think is appropriate here:



I'm in no hurry, but I think that a K5 body would look good on here if I could get it mounted low without having to chop it up too badly. My 1:1 crawler is a K5, but this car is closer to my friend Andy's sand dragster K5... here's his maiden run on his freshly built 1400+hp 604ci bbc, I suspect that a change of underpants was in order!:

https://www.google.com/url?sa=t&sour...VoDNSf2uPtngJw

^^^SERIOUSLY, WATCH THAT VIDEO^^^

[TheLetterJ]

I threw the stock rtr Ripsaws on for a little test and tune. 14/54 is too slow. I thought I had more 32p pinions, but the only other 5mm shaft one I had was a 19 so I gave that a go. I had to shave a little more off the right/rear link mount, and even a little bit from one of the lugs that the skid plate bolts thread into.

19/54 is the tallest gearing that is going to physically fit, and I'd say that top speed is about what I had in mind, maybe even a touch too fast... but the acceleration is pretty weak. The way I see it, I either need to go 4s and gear back down, or I need a bigger motor.

I know that a 3660 will fit if I space the trans up, but I wouldn't be gaining all that much wattage. 1/8 scale 4074 or similar would certainly gitrdun, but that sounds like it's going to come with its own set of headaches. I guess more voltage is my easiest option.

What to do. What to do. Hmmm.

[valheru]

Looking good.

[Growler]

Originally Posted by TheLetterJ

I'm sure I'll be playing with the spur/pinion gearing, but I want to beef up the trans before the maiden voyage. I'm kicking around a few options and would like to hear some opinions:
...
4) just throw some HD gears in the stock cases (2.6:1)
...
#4 is cheap, but I have my doubts about the plastic housing living very long so I think I should probably skip this option?

Thoughts?

I am actually thinking of using the plastic housing. I got a GPM alu transmission case for my FOFF build but all holes meant for holding bearings and middle gear shaft seem horribly large. There is considerable play in assembled gearbox, stock plastic one seems a lot more solid in that respect. Maybe not a big deal for crawling or not a big deal at all but my inner feeling tells me not to even try it on a FOFF rig. Only problem is that the plastic case is out of stock in shops from where I usually order my stuff. The one I have is already used as a trail crawling gearbox and I don`t want to wreck it and be left with a metal case that could cause excessive wear on related parts.

[TheLetterJ]

My stock trans housing had only been used for 800mah of 3s before I tore the whole rtr apart only to turn it back into a kit, so it was still in new condition. I did bench test my brushless motor while attached to the stock plastic transmission and I could feel the case halves wobble separately from each other. That is what started my search for better cases and internals. I have seen someone put bushings in the stock case halves for the idler gear shaft to ride on, and that, along with lots of grease, would probably hold up for quite a while with steel gears and a sensible power system.

While I know that the Hot Racing cases are a popular and proven option, the rest of my setup would have left me disappointed with the lack of speed... had I been using a 5000kv+ motor it would have still been a good choice, but that high kv would have ruled out 4s so I'd be stuck with 3s power. If for no other reason than that, I'm glad I went with the 1.8:1 trans vs everybody else's 2.6:1

The SSD high ratio transmission kit reuses the top shaft, top gear, clutch, gear cover, and idler shaft from the stock Wraith trans. After assembling it and running it on the bench (not bolted to the skid) it had none of the wobble that the stock output shaft/cases had, it felt very solid. The bottom gear uses a pin through the output shaft, much like a wheel hex pin through a stub axle. I put a few drops of thread locker into the recess of the bottom gear/surrounding the pin, in hopes that it will eliminate any shock loading. Time will tell if it is even an issue. I'm not at all concerned about the cases at this point, and it sure does look nice! One of the most "scale" looking transmissions out there for the Wraith if you're concerned with that.

My goal with this car was to try to build things ONLY ONCE so I believe the rest of the car should be up to the power of 4s. I'm already kind of wishing that I had just started with a 3660 sized motor, but I don't think it will be worth the $$$ to get another 200 peak watts of power output at this point. My ESC can handle more motor and voltage. We'll see what 4s does with the rest of the car as-is, hopefully that does the trick, because my Baja Rey is demanding more money now!

[TheLetterJ]

I made a few last minute tweeks yesterday in preparation for today's beach run. I swapped out some revo rod ends for jato rod ends which pushed the rear axle back another 9mm so I'm pretty well maxed out for wheelbase at ~365mm. I also moved the front shocks to the center hole of the upper mount. During my trial front yard pass, my last spare servo (coincidentally the original axial/futaba? from this car) died, luckily my buddy gave me a cheap JR from an old airplane to get me by for today's run.

We headed out to the Pismo dunes nice & early with the goal of being out before the holiday crowds took over. I've got to say, the Wraith performed better than expected. While it was no powerhouse, it was able to go up everything I pointed it at, starting from a dead stop at the base of the dune. I was a little concerned that I may have gone a little overboard with the forward weight bias, but it really shined on the steeper dunes where my buddy's erevo (4x 3.8 paddles and 4s) would wheelie/backflip, or dig in if he didn't hit with some speed. Speaking of speed, I'd say it was just right. Fast enough to be fun in more open sections, and carry enough speed to catch a little air off the top of the bigger dunes I tried.

Now I've got a short list of things I want to do before taking it out again, but overall, I'm pretty happy with the way this car came together. The SSD hi-ratio transmission was the right choice for this car.

Sorry I didn't get any action shots of the Wraith, but here's proof that it left my workbench!:

[TheLetterJ]

I took the wraith to the riverbed (dry 99.99% of the time) last Sunday and killed the borrowed servo on the second backflip, so I borrowed a towerpro mg958 off my Redcat. That $11 servo has held up to the abuse thus far.

I took my family out again on Memorial day and met up with a few other local rc enthusiasts. I already knew my battery was insufficient, but it got to be downright frustrating on bigger dunes. I'd be doing great and then 10 seconds later the car would "stall", wait a few seconds and it would go again... a sure sign that the c rating was too low. We still had a good time!



My buddy with the erevo asked me to go to the dunes again this morning and I didn't have anything else going on, so why not? Since the last outing all I did was install a Hot Racing rear swaybar using the stiffest of the 3 bars, with the links on the closest (stiffest) hole. The swaybar effectively locked out the rear suspension articulation, so it pretty much only goes straight up and down. It definitely goes where you point it now, but I might try the medium stiffness bar to keep the rear wheels from bouncing around over sand ripples.

After about 10 minutes, the car just stopped and the battery had puffed enough to split the hard case. Meh. I saw that one coming. I ran a borrowed pack with 150amp constant discharge and the Wraith did fine with no stalling. Now that I have no choice but to buy batteries, the question is: do I go with 2) 2s's in series, or 1) 4s?

Proof that it moves under its own power!:

[TheLetterJ]

I got my 5500mah 40c 4s GensAce battery yesterday. Perfect fit. It ripped up my front lawn (sorry honey!) on takeoff, so I think I'm getting close. I know I need a few more things to get this car "reliable" and I really shouldn't take it out again until I get:

A new tx/rx (still using the Axial branded one which seems to glitch a lot and has pretty weak range) Will I be happy with a FlySky GT3B, or should I hold off until I can afford a Spektrum DX4_?

Servo (so I can put this one back in my crawler) The $11 TowerPro mg958 has enough speed and power for this application, and it hasn't died yet, so maybe it's not so bad? The only other 2 I'm currently considering are the Savox 1283sg, or Promodeler 470. I don't really need more power here, but those 2 have proven to be just about as bomb-proof as they come.

BEC to help reduce heat/load on the esc. The 6v/3a built in bec seems to be adequate for the current servo, but the esc is pushing pretty hard as the motor is regularly pulling over 100amps. An external bec could only help reduce heat.

Dlux U4 truss to allow more front compression clearance, make the front housing bomb proof, and it just plain looks cool.

Extend the motor leads and reroute them (currently running OVER the battery.)

I'm kinda eyeballing the Dinky RC "wedge" cowl induction hood since it would make an air gap above the esc's fan and a much more open path for heat to escape, but I wouldn't say that's a "must have" item just yet.

I might have to shelf this until I can finish it up right (but I'll probably just continue running it, and complaining about its known shortcomings!) or sell/trade off some stuff to fund this car. We'll see. The crazy wheels in my head keep turning and the thought of selling one of my motorcycles to buy rc stuff keeps entering my mind. Must. Resist. Like I said, crazy.

[bongsten]

My buddy used to run the GT3C in the dunes and it had weird range issues esp if the truck was below us. I had an older DX4 and it worked fine and im futaba now also with no issues. Is there a crawler scene in Santa Maria? im in SLO and its dead here.

[TheLetterJ]

My dx2e has more range than I'm comfortable putting to use, which is why I was thinking I'd buy a better Spektrum radio... until I started pricing DSMR receivers. Nope. My usual rc partner in crime runs a dx4s with his race buggies/ sct's, but runs the gt3b for everything else. The gt3b has much better range than my crappy rtr axial radio, but like you said, it still loses signal when the car drops below grade, my dx2e maintained signal when I drove my Baja Rey into a 20'+ deep sand bowl about 3-400' away.

I'm 99% sure I'm going to buy a Radiolink RC3S (4ch) as it's supposedly nearly the same functionally as a Futaba 4pl and it also uses FHSS like Futaba. I know it's still a cheap radio, but it seems like a better option than the FlySky, for about the same price. Receivers are around $11, or $16 with a gyro, so it will be more affordable for me to use with more cars.

There's not much (any?) of a crawler scene here either. There's definitely a few die hard rc guys, but with no hobby shops nearby, it's kind of hard to rally the troops. I always stop by Hobby Headquarters if we're in the Atascadero area as they seem to have a pretty good selection of crawler stuff, but it's still unrealistic for us to keep most of our purchases local or encourage newcomer's to join in when "local" is almost an hour away. I've tried to get a few of my friends interested in crawling, but that was very short lived.

Oh well, there's a few guys that always seem to be up for running some sort of rc, and my kid's are interested, so that's good enough for me! A few of the guys that I run with are on the FB group "805 SLO RC" and arrange semi-frequent meetups, but rarely any crawling. I'm not on FB, so apparently I don't exist.

[bongsten]

Yea i tried to meet up with them at the dunes once but couldn't find them and i don't pay enough attention to fb these days. I used to run the 2 speed setup when i had a wraith it was cool but the shift servo was too close to my sensor cable and i always seemed to have issues but it may have been the harness for my bec not being grounded properly

[TheLetterJ]

Photobucket can suck it, so I've got nothing to show, but I did order eveything on my to-do list.

For the radio, I went with a Radiolink RC3S. I'll pick up one of their gyro receivers next time, it might actually be usefull on a 30+mph Wraith.

I bought (2) Towerpro MG958 servos, cheap enough to keep a spare on hand, especially since it will fit any of my 1/10 cars. I really wanted to step it up on the servo, but I was able to get a lot more done on the car by cheaping out here... it has the speed and power this car needs, and has held up well so far, so no regrets here.

Dlux U4 black anodized, remachined, front axle truss.

Castle BEC, will set at 6.6v.

12g silicone wire and 4mm bullets for my motor leads.

I won't have it done this weekend, but hopefully she'll be all set for some dune action by next weekend. I can't wait to see how it does on 4s! With my Baja Rey being 4wd again and having a new set of panther paddles, the Wraith needs to step it up!

[TheLetterJ]

Not that I've finished up this round of projects, but assuming that it will all go together okay, I've already got the wheels in my head turning for the next project...

With the Dlux truss allowing more uptravel without interference, I can see that suspension should probably be my next step. I know it will never keep up with even most sct's in the suspension department, but I think it could be worth switching to a rear trailing arm setup to milk a little more travel out of this thing without gaining ride height. Remember, sand toy, not competition foff or crawler.

If I go with a bomber skid/trailing arms, do I even need to relocate the upper shock mount? It almost looks like the shock could still mount outboard on the flipped stock upper mount (instead of inboard like when running trailing arms with a wraith skid) with the wider spread of the lower links when using a bomber skid? If not, maybe with the help of a "droop kit" to get the shock up/forward a bit more all would be well?

I know that the stock bomber skid is cheap, and will physically bolt in the wraith chassis, but then I'd have to adapt my tranny to it (which is easy enough) and I'd have the big dip in the belly. But... I like how the Circle City RC bomber skid is flush with the sides of the chassis, has Wraith transmission mounting holes, and should cleanly fit a 3663/550 motor (maybe bigger?) should I decide to switch motors later. The only downside I'm seeing is that my interior may not fit without chopping it up. Either bomber skid would also have the benefit of raising my upper links at the skid end for supposedly improved anti-squat characteristics.

Anyone care to shoot a hole in this idea, or am I on a good track?

[TheLetterJ]

I got sidetracked while installing the Dlux U4 truss... the VP "zero ackerman" steering arms were prematurely contacting the ends of the truss, severely limiting my steering angle.

At first, I tried spacing the arms up, but I would have had to space them up about 3/16" to get the clearance needed to hit the steering stops, even with the tierod mounted on top of the arms.

I figured that different steering arms would likely be the fix, so I started looking to see what was available. Although a few options looked like they would get me close, they looked like they would only be true ackerman with a 20" ish wheelbase. The longer arms would have cleared up my tierod interference, but would not help to correct my ackerman, so I decided to make my own.

I drew a 1:1 diagram of my Wraith's wheelbase, front axle king pins (knuckle bolts), steering arm mounting holes, and rear axle's centerline, and drew lines from each kingpin intersecting at the center of the rear axle. I knew the VP arms weren't on the money (which is understandable considering that every different wheelbase/front axle kingpin-kingpin width would need a different offset arm) but I was surprised to see how far off they really were. Their "racing ackerman" arms would have just been even further off in the same direction. My new arms have the tierod holes nearly 5mm further outboard (per side) vs the VP arms, and are perfectly in line at 0° ackerman, and 20mm from the kingpin which gives me a 1:1 ratio of the steering arms to my servo horn.

I transfered my drawing onto 1/8 aluminum plate and drilled the 3 holes. I drilled the 2 knuckle side holes to 1/8" and then counter sunk them. I drilled the outer/tierod hole to 3/32 and will tap it to 3mm once I replace my broken tap. After the holes were drilled, I cut the plate with a thin cutoff wheel and smoothed the edges with a drum sander.

With the new arms bolted down I unthreaded the revo rod ends on my tierod until I had a tiny bit of toe out. I'll switch to cut-down jato rod ends after I make sure I'm happy with the toe. After that, I cycled the steering and had a little interference when the tierod was mounted below the arms, so I counter sunk the outermost screws on the truss and that cleared it up. This setup fits inside of a 2.2" wheel with the tierod under the arms, but will need wider hubs for the top mounted draglink to fit... no problems fitting inside of my 2.8"s.

I ended up with 59° of steering at the inside tire (obviously the outer tire now turns less) and proper ackerman geometry, so I'm pretty happy with the outcome even considering that it took me a couple hours to get it there.

Slowly picking away at this!

[TheLetterJ]

I've got a couple runs on 4s, and it just doesn't work like I'd expected it to. I've had problems with this ESC (and maybe the motor too?) from the get go, it never ran with the sensor wire hooked up (even when I tried it with a borrowed, known good sensored motor) cogs like crazy at anything much less than full throttle, and it just never could deliver the kind of power that I anticipated. I would say that it has about 2/3 the power that I'd expect, which likely explains the problem.

Either way, the ESC took a dump tonight, it just would not go. No overheating, no burnt electronics smell, fan still running, steering still working. Motor still works when plugged into another (non sensored SC ESC, so I think I'll take my chances with buying a new ESC and still running this motor. So my question is:

Which ESC?

I've been researching for some time now (knowing it will probably be a few months before I can squeeze it in the budget) and have pretty much narrowed it down to two choices, Castle Mamba Monster X, and Hobbywing XR8. The MMX has one clear advantage of being able to toggle settings with the aux wire, and from what I've been able to find, it has a 120 amp rating (which is why I'm considering the MMX and not the smaller Mamba X.) The XR8 also has a strong BEC with adjustable voltage and a 140 amp rating which would better accomodate the larger 3668 size motors (2000+ watts, or about 135 amps on 4s) that are a strong possibility if I end up replacing the motor too. I've run with a few guys that happily run the XR8 in their 1/8 buggies, but we're not tight enough for me to ask to borrow their speed controller for a test run.

I've had really good luck with all of my other Hobbywing stuff (most of my brushed and brushless systems are Hobbywing) which is why I'm still considering their products. Should I just take the uber high powered motors off the table and enjoy the wider range of use that the MMX's aux wire could give me, or go bigger and choose the XR8? What do you guys think?

[TheLetterJ]

So there I was...

Digging through my rc stuff to see if I had anything worth selling to fund my new ESC. I still had my nearly new AE2 ESC and 20t brushed motor. I figured that combo was probably worth $25 to somebody... and then it hit me. I'd rather have this car up and running, even on a brushed setup, than getting just 10% the price of a new power system out of it. I grabbed a spare receiver and plugged the esc in, then plugged in a, wait for it, 4S! To my surprise, it did not light on fire!

Knowing that even if the AE2 lives a reasonable lifespan on 4s, the little 540 would die an early death pushing 4 big paddles. I asked a couple buddies if they still had their old Titan 550's laying around, so I now have a 12t in my possession. I was hoping to find a 21t, but the 12t sounds perfectly happy at full throttle. I'm gonna run it.

I have no idea where to start on gearing, but I think I'm going to start at 15/54 and see if it has enough power to pull it... or if it can survive a full pack.

Weather permitting, I hope to take it out to the dunes next weekend. If it lasts the day, it will have been worth it. If nothing else it should be a spectacular show of sparks!