Build Thread D3MON's D-28 Drift

[D3MON]

updates after printing and some revisions!!
believe i got my adjustable chassis hammered out.
printed and fitted lower chassis adjustment:

underside:

Upper adjustment:

Printed:

this allows for adjustment from 98mm through 108mm in intervals of 2mm, with the slotted holes on the bottom of the chassis for the adjustment there.
so far this seems to work really well and easy to adjust. will make revisions if i dont like how it wears, or operates later.

NEXT, is the battery hold down, which i am still on the struggle-bus with, with the size of the battery I'm trying to use.

the holes from the bottom with the posts make the entire chassis wider than i want, trying to come up with ideas for a very low profile holder that is secure and doesn't protrude down or up, though i am starting to think its just not possible.
i do have an idea, but it does require a battery tray on top of the chassis as to not have anything hanging down.

rubber band/top side hold down idea:
(also seen in picture above printed and fitted.)
the one side as seen below with the hinge will have a small rubber band on a ball end anchored to the right rear upper chassis brace/RX post.

fitted:

if this works how i want, eventually i am going to design in multiple widths for different battery sizes, which the front battery holder also opens up to be able to be adjustable, or have different sizes to be able to accommodate.
if the rubber band side does not prove to work well, i am going to repeat what the other side does so it will just pivot on one screw. current line of thinking for not doing that now is i dont have a shoulder screw that small/correct dimensions, and it will eventually get floppy/worn out.



As you can see in the underside pics showing the front chassis (god awful looking because of floating on supports)

i still haven't decided how i am going to keep a similar profile above to allow clearance of the servo horn, while moving it vertically up 1.25mm. i am sure that 3d printed PLA has enough flex that it wouldn't be a problem, but there are some future plans with materials that wont.

anyways that is all the progress so far! going to try drawing up and printing some drift tires here soon (thinking TPU 85?, or might just do PLA+), and might have access to a gyro that will fit on the chassis to give it its first test run.

thanks for reading another wall of text! but at least pictures this time.

 

[Doom!]

Sheesh, what's taking so long? Seriously, I can't believe how fast your working through this. Really enoying this build.

 

[D3MON]

Sheesh, what's taking so long? Seriously, I can't believe how fast your working through this. Really enoying this build.

at times it feels like trying to swim up a waterfall of molasses, but for the most part i am really happy with how the pieces are kind of just falling together, also really helps with the tips and encouragement from you guys!

 

[WickedFog]

at times it feels like trying to swim up a waterfall of molasses, but for the most part i am really happy with how the pieces are kind of just falling together, also really helps with the tips and encouragement from you guys!

It's looking great! And your design skills are on point.

One thing I would suggest is instead of using those screws, I have found that regular machine screws, just like the ones in our RC cars, seem to work best for screwing into PLA/PETG. The smaller threads do less damage going in, and as long as you adjust your hole sizes accordingly, they will get a helluva bite in the plastic. I typically use flatheads wherever I can, so I model the countersinks in a tad heavy so the screw heads sit below the surface.

That's one of the killer features in Fusion. You can go to McMaster and import the fasteners right into your model. It helps with putting together hardware lists, hole depths, etc.

Great thread man! It will be a featured thread in the next round.

 

[D3MON]

got it all put together and actually did a short test drive earlier today.

still trying to learn how to drift etc. i am using a Yeah Racing Hackslider mini, of which i am trying to learn how to use as well.
I have learned that negative gain is definitely not the play, was damn near undriveable. not knowing what i am doing decided to start with -100 then move up in increments, which around 50+ was getting easier to slide around and have control. unfortunately had my first issue at that point which i was troubleshooting a toe gain issue and i didnt re-tighten one of the steering links to the servo horn.

that said almost immediately it got tore back down to this:

you can kind of tell in the pictures the rear tires are wearing a-typically and also on the outer edge.
i ran out of adjustment for the camber and the holes were drilled by eye placement to locate the upper links (was a temporary fix until confirmed proof of concept).

Reprinted the rear gear box halves with the holes in consistent locations.

I am extremely pleased that as designed the gearbox module was able to be removed as a unit and minimal other teardown.

I WAS going to attempt to tackle rear wheel issue from the first page or so to get a correct rear spool shaft length.
the rear hub carriers have been re-designed alongside a-arms to reflect the correct track width, BUT and a big BUT i ran into a major issue.
My spool gear is the same size as my spur... now this doesn't sound like a major issue until the idler/jackshaft gear comes into the picture.
at the moment the idler gear is 12T, now with a .5m tooth pitch, this makes the nominal size of engagement approximately 6mm. this is smaller than the diameter of the axle shaft dogbone, and the width is such that the dogbone perfectly hits the center of the spur gear.

few fixes off the top of my head:
Option #1: put the spur gear shaft further out on the jackshaft/idler shaft, but this is going to be really wide AND it will start hitting the rear hub carriers as designed. (might have a fix for this, will have to do some testing)
Option #2: (imo most viable, but alot of re-design) increase the size/tooth of the spool gear, and possibly increase the idler gear, and rotate the idler gear location planetary to the spool shaft (up).
Option #3: add an actual idler gear between so i can gain more space. i really dont want to do this one near as much as adding another 3d printed gear to the mix and the issues that entails).

going to think on these options awhile or until i get actual (non-3d printed) wheels/tires for a more production application.
through all that was able to get the camber in the rear adjustable to have negative camber.
(teaser in the background for the body I'm going to be using oops!)

anyways its all put back together and hoping to have some time to practice in the garage soon!

thanks again for following the build!

 

[D3MON]

It's looking great! And your design skills are on point.

One thing I would suggest is instead of using those screws, I have found that regular machine screws, just like the ones in our RC cars, seem to work best for screwing into PLA/PETG. The smaller threads do less damage going in, and as long as you adjust your hole sizes accordingly, they will get a helluva bite in the plastic. I typically use flatheads wherever I can, so I model the countersinks in a tad heavy so the screw heads sit below the surface.

That's one of the killer features in Fusion. You can go to McMaster and import the fasteners right into your model. It helps with putting together hardware lists, hole depths, etc.

Great thread man! It will be a featured thread in the next round.

thanks! really appreciate it!

for the most part i am using M2 x 0.4p machine Panhead screws everywhere, except the underside where i am using flathead/recessed.
my train of thought is/was that where i dont need them fully countersunk, the panhead wont deform/spread the PLA especially when i only have 1mm of thickness to anchor to and if it spreads it, it will bind.
I was initially trying with 0.5mm chamfer to full recess the flatheads to be flush, but i am finding that that wasn't enough and probably need to go to 0.75mm or even up to 1mm chamfer.

i am using a few M1.6 screws for linkages, though M2 would probably be more than fine, but i just dont have enough long M2 screws to trim the head off to use as threadrod.

i will have to look into importing fasteners for sure!! was going to go through and hand count them, but if i can do that will be loads easier i believe. going to have to figure out how to do that in the next few days.

i am just happy to post/share my build lol

 

[WickedFog]

thanks! really appreciate it!

for the most part i am using M2 x 0.4p machine Panhead screws everywhere, except the underside where i am using flathead/recessed.
my train of thought is/was that where i dont need them fully countersunk, the panhead wont deform/spread the PLA especially when i only have 1mm of thickness to anchor to and if it spreads it, it will bind.
I was initially trying with 0.5mm chamfer to full recess the flatheads to be flush, but i am finding that that wasn't enough and probably need to go to 0.75mm or even up to 1mm chamfer.

i am using a few M1.6 screws for linkages, though M2 would probably be more than fine, but i just dont have enough long M2 screws to trim the head off to use as threadrod.

i will have to look into importing fasteners for sure!! was going to go through and hand count them, but if i can do that will be loads easier i believe. going to have to figure out how to do that in the next few days.

i am just happy to post/share my build lol

The head diameter is twice the screw diameter. M3 for example takes a countersink with a 6mm major diameter. With 3d printed countersinks, add .2 to that, but this adjustment will depend on your printer. So if you model your hole .5 bigger, that's 3.5mm. Add the .2 to the 6mm diameter, so 6.2. 6.2 - 3.5= 2.7mm ÷ 2 = 1.35mm chamfer size.

In the ribbon bar you see insert>>McMaster component. It will open a browser window. Find your component, click it's part number to select the size you want. Click the dropdown and choose STP. Make sure to choose the unthreaded option for screws and nuts.

From there you choose the joint commands and I always snap the top diameter of the screw and top diameter of the chamfer. You should see a .1mm gap between the chamfers if you look at a cross section of the center of the hole if you did it right.

 

[HPIguy]

I typically use flatheads wherever I can, so I model the countersinks in a tad heavy so the screw heads sit below the surface.

I hate flatheads with a passion that few can muster. Why on earth would you not use anything but the archaic flathead? Torx, hex, phillips, anything but flatheads IMHO.

 

[D3MON]

I hate flatheads with a passion that few can muster. Why on earth would you not use anything but the archaic flathead? Torx, hex, phillips, anything but flatheads IMHO.

lol i believe there is a difference of terminology here, Flathead is a type of countersunk screw i.e.

i believe the "flathead" you are referring to is the slang term for slotted screws which are these:

slotted (except for certain scenarios) are the worst thing to ever encounter when working on about anything lol

 

[WickedFog]

I hate flatheads with a passion that few can muster. Why on earth would you not use anything but the archaic flathead? Torx, hex, phillips, anything but flatheads IMHO.

Flatheads

 

[HPIguy]

I've always heard those referred to as beveled head, or countersunk. Never heard them called flat head. But it makes sense, as I'm familiar with button heads. My faith in both of you is restored, carry on. LOL

 

[WickedFog]

I've always heard those referred to as beveled head, or countersunk. Never heard them called flat head. But it makes sense, as I'm familiar with button heads. My faith in both of you is restored, carry on. LOL

That's because folks over the years have decided to start calling straight screwdrivers flatheads

It's like my son informed me that Antarctica is now considered to be a desert. We go round and round about that one!

 

[CertifiedMike]

I hate flatheads with a passion that few can muster. Why on earth would you not use anything but the archaic flathead? Torx, hex, phillips, anything but flatheads IMHO.

You hate flatheads? You're a flathead hater???
I have a flat head!!!

 

[D3MON]

not really an update so much as just sharing thoughts and seeking a little guidance lol

Test drove the chassis again today, very slightly starting to get the hang of how to drift.
going to try getting some videos once i get a bit better. with the chassis itself i am pretty pleased so far!
that said, i am getting pretty frustrated with the shocks.
For the record, yes i understand they are just cheap chinesium knock up upgrades for a more or less knock off cheap car, but this is the second time the shock bottom managed to un-thread itself.

Not even exactly sure how its possible! let alone same shock doing it twice!!

Really want to figure out another shock to be able to use, but it appears most small scale drift cars either use cantilever suspension (really want to incorporate this chassis to be able to use eventually), or utilize some sort of captured spring. this may be a possibility, and might try playing with it.
and even looking at general cars, i am having difficulties finding anything other than scx24 shocks, may be possible but they are approx 10mm longer.

If anyone has any ideas or insight into shocks between 18mm through 24mm id be very grateful!

Also i mange to identify the cause of the toe gain on the front left corner (i think).
the left lower ball end is sitting approximately 0.5mm further back, both reducing to almost 0 deg camber from 8 deg, but also just changes all the geometry.
I've identified it as either the arm hinge holes got misaligned when drilling them out, or the hole through the arm that gets the long 1.6m screw to the ball end became off centered.
If its the former, easy enough fix, just be more precise while drilling the hole. (test printing a few more arms currently)
I do drill the hole to 2mm which gives more precise consistent fit with the m2 screws fits that act as hinge pins.

The latter... i do not understand how it happened, but with me as an operator i wouldn't put it past me to figure out how to mess it up.

currently in the fine tuning of the design aspect. Up on the agenda is:
learn to drive XD
play with shock tower heights. I dont have a way to limit droop so relying on the shock maxing out do it for me, but also i want to have good ride height.
fix the front end nose drop.
Start to make an off-shoot/upgrade version
Figure out a way to revise the front shock tower to utilize a plate. going to do this by incorporating a bumper/lower chassis mount to connect it to on the bottom.
make the RX able to be a plate with mounts to secure the battery hold downs (ins?)
rear shock tower, revise to able to use a plate.

well thats it, hopefully more pics and a video here soon if i have time to run it more.

 

[Doom!]

The shocks performance or lack there of is quite shocking. (See what I did there, yep I'm a dork.)
IS this smaller than an scx24? Would a setup like a Kyosho Mini Z work better?

 

[D3MON]

The shocks performance or lack there of is quite shocking. (See what I did there, yep I'm a dork.)
IS this smaller than an scx24? Would a setup like a Kyosho Mini Z work better?

dont worry that comment hasn't "dampened" my spirits.
yeah unfortunately this is smaller than a SCX24, shortest I've found for SCX24 is 34mm, which is about 10mm too long. the mini-z cars from what i can tell all use a single lateral shock in the rear, or an encapsulated spring built into the a-arm. the mini-z buggy also is about the same length as the SCX24 coming in at 34mm

 

[Doom!]

Gotcha, just wasn't sure how much difference there was. I'll keep my eyes peeled. (Wait that sounds painful).

 

[WickedFog]

You looked at Orlandoo shocks? They are for 1/28-1/32, but they might work. Helidirect deals with all kinds of small scale, so I'd look there.

Or just put a dab of blue loctite on those shaft threads.

 

[Lukedavis]

Probably not, but would losi micro b front shocks work? Ill go find some measurements

 

[Lukedavis]

Yep won't work. Eye to eye is 33mm