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Thread: Wraith trans choices for sand/dunes

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Old 04-18-2017, 12:33 AM   #1
Quarry Creeper
 
Join Date: Feb 2016
Location: Santa Maria, CA
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Default Wraith trans choices for sand/dunes

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?
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Old 04-18-2017, 01:01 PM   #2
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Default Re: Wraith trans choices for sand/dunes

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.
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Old 04-19-2017, 12:08 PM   #3
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Default Re: Wraith trans choices for sand/dunes

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?
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Old 05-10-2017, 01:47 PM   #4
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Default Re: Wraith trans choices for sand/dunes

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:


Click the image to open in full size.

Getting closer:

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Old 05-10-2017, 02:27 PM   #5
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Default Re: Wraith trans choices for sand/dunes

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.

Click the image to open in full size.

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

Click the image to open in full size.

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

Click the image to open in full size.

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^^^
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Old 05-11-2017, 11:13 PM   #6
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Default Re: Wraith trans choices for sand/dunes

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.
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Old 05-12-2017, 04:15 AM   #7
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Default Re: Wraith trans choices for sand/dunes

Looking good.
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Old 05-13-2017, 01:01 AM   #8
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Default Re: Wraith trans choices for sand/dunes

Quote:
Originally Posted by TheLetterJ View Post
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.
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Old 05-13-2017, 01:41 AM   #9
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Default Re: Wraith trans choices for sand/dunes

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!
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Old 05-26-2017, 09:22 PM   #10
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Default Re: Wraith trans choices for sand/dunes

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!:

Click the image to open in full size.
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Old 06-04-2017, 05:47 PM   #11
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Default Re: Wraith trans choices for sand/dunes

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!

Click the image to open in full size.

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!:

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Old 06-13-2017, 06:15 PM   #12
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Default Re: Wraith trans choices for sand/dunes

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.
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Old 06-18-2017, 10:16 AM   #13
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Default Re: Wraith trans choices for sand/dunes

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.
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Old 06-18-2017, 02:53 PM   #14
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Default Re: Wraith trans choices for sand/dunes

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.
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Old 06-18-2017, 04:12 PM   #15
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Default Re: Wraith trans choices for sand/dunes

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
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