Build Thread D3MON's D-28 Drift

[HPIguy]

really appreciate it!
i do have about 3.5mm of total adjustment to slide the servo forwards and back. right now its mostly far back, i have it as close to what i can see most drift builds that are running and not just flexing steering angle are doing.
i do need to redesign the front shock tower as the servo horn is really close to it so i dont have much room to slide it forward as the slider adjustment allows. may be asking for tips on drifting here before long lol
was able to run it a bit on my lunch break, starting more and more to get the hang of it, though i believe i am having either servo issues, or possibly RX or gyro issues. going to take the servo out of my scx24 to compare, but it gets really twitchy randomly. mostly leaning on servo because i know the wires are a pulled some from bending them back to mount the servo however many times i have designing it.

I'm just learning myself, but I'm more than happy to answer anything that I can. If by twitchy you mean the front tires shaking back and forth while running it, your gyro gain is too high. And, I've learned that while I didn't have the twitchy issues, I was running way to much also. It should honestly feel like a real car, to the point you can spin out with too much throttle. Otherwise, you won't be able to hold long drifts, and transitions won't be fast enough. The gyro is there for an aid, but not a crutch. You still have to learn to drive the car with throttle and small steering inputs. I thought my setup was great, until I drove a friends well-tuned car on his private track, and I proceeded to just spin out endlessly for a good five minutes, until he added a small amount of gyro gain, and I slowly started getting the hang of it. It's a completely different world from anything RC that I've ever done for sure.

 

[D3MON]

I'm just learning myself, but I'm more than happy to answer anything that I can. If by twitchy you mean the front tires shaking back and forth while running it, your gyro gain is too high. And, I've learned that while I didn't have the twitchy issues, I was running way to much also. It should honestly feel like a real car, to the point you can spin out with too much throttle. Otherwise, you won't be able to hold long drifts, and transitions won't be fast enough. The gyro is there for an aid, but not a crutch. You still have to learn to drive the car with throttle and small steering inputs. I thought my setup was great, until I drove a friends well-tuned car on his private track, and I proceeded to just spin out endlessly for a good five minutes, until he added a small amount of gyro gain, and I slowly started getting the hang of it. It's a completely different world from anything RC that I've ever done for sure.

OK good to know! from the testing i have done so far i did not see any of the "jitter" effect when quickly moving the back end back and forth. it was more like it would just completely cut out, or in the same semi-steady drift, randomly full lock the same direction of the drift, or opposite, would also do it when going more or less straight, would turn sharp on its own a random direction then go back as if nothing happened.
it hadn't done that the first few times driving the car that i noticed.


Another thing i realized is i ended up getting the wrong servo anyways. i ended up getting the Emax ES08M"A" II which is the analog version, not the ES08M"D" II which is the digital version, and so far from what i am reading/have read is sometimes the Hackslider mini can have problems with analog.
though the first few tests i didnt notice any issues. i am running about 50 of 100 gain currently.
The servo i had in the SCX24 is quite a bit taller both on the motor/back side, but also about 2.5mm taller from end of spline to top of mounts and the spline count and size is different. i can make it work by adding spacers or making taller servo mounts and a new servo horn with a larger hole if the re-soldered emax servo has the issue persisting.

 

[HPIguy]

Ok, so here you go. Man these things are teeny tiny, and also 1/24 scale in my case. The threaded stub in my case is around 2.1mm long, hope that helps.

 

[D3MON]

Ok, so here you go. Man these things are teeny tiny, and also 1/24 scale in my case. The threaded stub in my case is around 2.1mm long, hope that helps.

thank you very very much! really appreciate all the pics and help with this so far! going to keep that in my back pocket for v2 of the chassis, along with the adjustable driveshafts.

 

[HPIguy]

OK good to know! from the testing i have done so far i did not see any of the "jitter" effect when quickly moving the back end back and forth. it was more like it would just completely cut out, or in the same semi-steady drift, randomly full lock the same direction of the drift, or opposite, would also do it when going more or less straight, would turn sharp on its own a random direction then go back as if nothing happened.
it hadn't done that the first few times driving the car that i noticed.


Another thing i realized is i ended up getting the wrong servo anyways. i ended up getting the Emax ES08M"A" II which is the analog version, not the ES08M"D" II which is the digital version, and so far from what i am reading/have read is sometimes the Hackslider mini can have problems with analog.
though the first few tests i didnt notice any issues. i am running about 50 of 100 gain currently.
The servo i had in the SCX24 is quite a bit taller both on the motor/back side, but also about 2.5mm taller from end of spline to top of mounts and the spline count and size is different. i can make it work by adding spacers or making taller servo mounts and a new servo horn with a larger hole if the re-soldered emax servo has the issue persisting.

Yeah, something's definitely not right then. Did you set endpoints in the radio before setting endpoints in the gyro? I've heard that can cause issues if not. Also, I think I paid almost as much for my servo (pre-tuned drift specific) as I did for my whole first cheap drift car. But, I haven't had a single issue from it or my gyro either one. If you keep having issues, the Dasmikro gyro is really good from what I hear, but probably has to come from across the pond. Stateside, I bought an AGF RC V3.5 and it was great in my 1/18 car.

 

[HPIguy]

thank you very very much! really appreciate all the pics and help with this so far! going to keep that in my back pocket for v2 of the chassis, along with the adjustable driveshafts.

More than happy to help anytime. I'm thoroughly enjoying watching this thing come together!

 

[D3MON]

Yeah, something's definitely not right then. Did you set endpoints in the radio before setting endpoints in the gyro? I've heard that can cause issues if not. Also, I think I paid almost as much for my servo (pre-tuned drift specific) as I did for my whole first cheap drift car. But, I haven't had a single issue from it or my gyro either one. If you keep having issues, the Dasmikro gyro is really good from what I hear, but probably has to come from across the pond. Stateside, I bought an AGF RC V3.5 and it was great in my 1/18 car.

if i eventually get good enough and enjoy it enough, i probably will spring for a good solid servo and one of those gyros for this guy, that said, after i re soldered the servo directly to the board i had no issues at all, got a good 15 minutes or so practicing figure 8s and such, and started getting the hang of it. still quite a few spin outs, but would get a few fig 8s in before that would happen. No doubt the actual tune is probably needing some serious love, but at this point i think i need to just get more wheel time in to understand what needs to be adjusted.

there is also the consideration that i am practicing on on a garage floor with most of the paint chipped/flaked off and pretty dusty, so not as consistent as optimal.

 

[HPIguy]

if i eventually get good enough and enjoy it enough, i probably will spring for a good solid servo and one of those gyros for this guy, that said, after i re soldered the servo directly to the board i had no issues at all, got a good 15 minutes or so practicing figure 8s and such, and started getting the hang of it. still quite a few spin outs, but would get a few fig 8s in before that would happen. No doubt the actual tune is probably needing some serious love, but at this point i think i need to just get more wheel time in to understand what needs to be adjusted.

there is also the consideration that i am practicing on on a garage floor with most of the paint chipped/flaked off and pretty dusty, so not as consistent as optimal.

Heck yeah! The biggest thing for me was ackerman, making sure my trailing wheel had less angle than my leading wheel, all while keeping my toe and camber, and caster where I wanted them. Something else to focus on once you get ackerman dialed is getting down at eye level, and make sure your front wheels have a good contact patch through their sweep range. If not, adjust camber and caster until they do. These mini cars are different from a 1:10 rig, and you usually don't want a ton of toe out and camber up front. Ironically, a lot of camber and toe out up front make the car really stable and forgiving, but really hard to transition, and on a p tile track, you'll just plow the front and barely get the car to turn. I'd imagine slick concrete would behave similar.

Surface makes a big difference for sure. I'm usually on kitchen linoleum, occasionally at my buddies p tile track, and haven't tried this one in the garage yet. But when I do, I'll make sure to blow it out and sweep it really good first. These small cars are dust and dirt magnets.

 

[D3MON]

reworked the front shock tower:

installed:

how it was previously the servo horn as it swung would get really close to the "back" of the tower.
previously i had talked about modifying the front to allow caster adjustment. it has been re-worked to adjust for this by shrinking the front arms down ~0.5m both front and back so that m2 washers could be added to adjust caster. this allows for approximately 6, 6.5, and 7 deg caster.
i am debating trying to change it to a slide system to get more adjustment, but at this time i dont know that it would be worth it, might be part of v2...

next up is the front battery locator.
right now the locator is static in place to hold a larger SCX24 (1100mah) sized battery. (57mm X 30mm x 16mm) eventually i probably will be updating to a more "standard" mini drift battery (45mm x 20/25mm x 12mm), but i also want to change it so if/when i do decide to share the files or to print the chassis for others they will be secured.

new lower chassis with slide for battery adjustment:

installed:

also the rear a-arm mounts have been extended by about 1mm forward and back. there is some play already so figured making a wider leverage point would help.

that is all for now, thanks again for following the build and Merry Christmas!!

 

[CertifiedMike]

Merry Cristmas!
This whole project is on a 'too tiny for me' scale but its always fun to watch you 3D wizards working thru these builds.

 

[HPIguy]

I'm still envious of y'alls CAD skills. "Hey this dont' work right," "it's OK, I'll design a new one." LOL

 

[Doom!]

Seriously, this has been a great build, and quite enjoyable to watch. hope we get to see some video of it in action when it's ready.

 

[D3MON]

I'm still envious of y'alls CAD skills. "Hey this dont' work right," "it's OK, I'll design a new one." LOL

lol its kind of funny you say that, i have been saving all the parts as i went that weren't straight up miss-prints, and thought it would be kinda cool to show all the rejected/superseded/prototype parts it took to get there.

not going to lie really expected a larger pile of parts!

 

[Doom!]

Looks like a pile of Lego when it's spread out like that.

 

[D3MON]

not wrong lmao

 

[D3MON]

Status update:
Christmas Eve was running the car and found a design flaw, well a few.... and a few "quality of life" tweaks i wanted to change.

Design flaw #1: this one was expected, and honestly surprised it still worked as long as it did, until it didn't.
the jack shaft uses a screw that the idler gear threads onto, and so does the spur gear. (Eventually when i go for metal gears this will be revised to just use a shaft and either a set screw or indexing pin, or both), under acceleration the idler gear can only tighten into a bushing so not an issue, but the spur gear also tightens, but tightens into an plastic spacer/bushing that presses into the bearing. Normally this would not be too much of an issue but it came to be for primarily two reasons, the spur gear needs a bushing before it goes on as locate it to the motor spur, and to give clearance to the motor mount. so to give the bushing enough material as to not just collapse it was pretty tight clearance to the motor mount. Second, it can and will keep itself tightened against a bearing in the trans half so it starts to generate heat.
Both of these lead to heat generation and melting the spacer to the motor mount and locked the car up solid.

decided to fix this by adding a set screw to the spur gear and adding a metal spacer to no close proximity plastic to plastic.

Design flaw #2:
I was getting pretty good bump steer, now i have no idea if it actually ever mattered for driving, but it bugged me.
it was pretty easy to identify the reason... the tie rod was definitely not parallel to the front a-arms. the hub mounts were as low as possible and still probably too low, and moving the servo horn up was not going to be possible as designed as they were already rubbing the front upper bulkhead.

ended up "flipping" the front bulkhead so the sliders actually attach to the top of it instead of the bottom. Now parallel components:

A few more major "QOL" issues:
moved the upper rear links outward, reducing length of the rear hub carriers.
revised the trans assembly to be fully contained as a unit. going to play with spool gear size, and will make it easier to quick swap gearing.
revised battery hold down components.

came to an understanding/realization that you CANNOT get SCX24 ball studs separately, ordered some Losi Micro B/T ones to test.

Also was able to come up with a way to use scx24 shocks in the front, at least the stock ones. Will be more expensive for someone to build as unless you find some used, new shocks are like 20$. good news is that buying a set will provide 6 studs (2 will be used).
biggest hope for this to succeed is that getting a variety of spring rates is possible. i removed the stock springs and am using the medium rate Hot Racing springs from the internal spring style.
unfortunately i can't figure out a way to make it possible in the rear.

almost everything got at least a minor tweak so... the car multiplied. 1.0 and 2.0 versions:
dont have electronics for the 1.0 so mocked up an esc/rx combo lol.

All the updates so far, back to needing to drive it lol.
think i like the design more than driving but TBD.

 

[D3MON]

Had some pretty good drive time with the car today, playing with adjustments to front camber and toe and seems to be getting easier to drive. one thing though is that i believe that my garage floor kind of constitutes as "high grip", i tried driving it inside a bit on the faux "hardwood" flooring and it slid a lot easier and i didn't need as much speed to hold angles and drifts and was a lot more controllable.
The "new" front shocks and design seems to have also really helped, both because they are a little lighter of a spring and aren't as "sticky/crunchy", kind of amazing that the metal is bad enough the aluminum body has marred the steel shaft....

anyone know how long batteries typically last in these? so far gotten about 30-40 minutes from this one pack and just hit 3.7v per cell
i am not sure if the ESC i have has LVC so been checking quite alot.

 

[HPIguy]

Good to hear you're getting on with it better. Batteries typically last a while because it's never really under load per say. My tiny 350mah packs will last for about 20 minutes or so before hitting LVC. My ESC gives no warning whatsoever, the car just dies mid drift. LOL

 

[D3MON]

Good to hear you're getting on with it better. Batteries typically last a while because it's never really under load per say. My tiny 350mah packs will last for about 20 minutes or so before hitting LVC. My ESC gives no warning whatsoever, the car just dies mid drift. LOL

ok thanks! I'm just worried that this cheaper esc has nothing and will drain my battery to 0v

 

[HPIguy]

ok thanks! I'm just worried that this cheaper esc has nothing and will drain my battery to 0v

Buy you a couple of these for now. Then, if you really love drifting, you can always upgrade your electronics.

https://a.co/d/6aRoA5l