SCX24 Specter Build!

[noel2]

I picked up this SCX24 a month ago (Dec 2019) with plans to do some serious upgrades, and this is where those plans have brought me.

I owned a Losi Micro Trekker a couple of years ago and always wanted to pick up one of Jim's Specter chassis conversions, but he'd just gotten out of selling the full kits and I wasn't super confident in my abilities to mod mounting plates, panels, links, and other miscellaneous bits. Now I'm a bit better prepared, and using a chassis with a lot more options in terms of upgrades (at the time I owned the Losi, it'd been discontinued and there was no more on-going discussion around the platform: that's still the way it is now sadly).

So here's the build! It's freshly started.

Huge thanks Fungi for designing this great chassis, GamyRC for tips on setting up and the motor mount, and Mod19RC for the 3D printed bits!

General Specs:
- Axial SCX24 Transmission and Axles
- 1/24 Specter Chassis by Fungi for Losi Micro 1/24 Crawler/Trekker
- PN Racing 130 70T motor with neo mags, silver brushes and a capacitor
- HR 43mm Losi shocks (modded)
- RC4WD goodyear MT/Rs on stock axial wheels w/CI micro soft foams
- Milstone overweights/wideners
- Emax ES09MD servo
- Shapeways Mod19RC steering links

 

[noel2]

Here’s a couple of pictures and a mod list before the specter build:

- Milstone overweights and wideners
- HR 57t Aluminum Losi Micro SCT Spur
- Losi micro T slipper set (used the two pads, one reversed, and the oring to mount the HR sct spur)
- Emax ES09MD servo
- Emax ES08MAII 3D printed servo mount (not needed)
- Mod19RC Steering Links
- RC4WD Goodyear MTRs on stock axial wheels (glued)
- CI Lil Nova Micro Soft Foams
- Relocated shocks w/pre-load and grease

It actually performed really well at this stage with only a slight lack of torque and some tire rubbing to be unwanted.






Some pictures of most of the parts I'm going to use:

 

[noel2]

Got the PN Motor mounted. Here are the parts I used:

-PN Racing 70t motor:
these are optional upgrades for the motor
• Neodymium Magnets *

• Silver Brushes *

• Capacitor *

- Aliexpress pinions 0.3mod 10t 2mm diameter (10 pack)

- Gamy RC 130 Motor mount V2

- Hot Racing 57t Losi Micro SCT aluminum spur

- Losi Micro-t Slipper (only the pads): used to mount the HR spur

- M2 Hot Racing Spacers: used to get the right spacing on the spur so it clears the transmission screws. Also used to properly space the motor onto the mount

- 2 14mm long m2 screws: used to mount the motor. these are course thread screws from mcmaster-carr

- Stock Wiring: soldered onto the PN Motor

I had to shave down one of the slipper pads, how I mounted the spur is shown. I used the m2 spacers to get the right spacing on the spur to prevent rubbing with the motor mount screws. I also used them to space the motor properly. Soldered up the motor and all is good.The aliexpress pinion has an inner diameter that's too small, so I had to drill it out to 2mm and glue it to the motor shaft. I'll see how well it works out.

All the parts used


The HR 2m spacers


Mount installed


1 of the biggest spacers and 1 of the smallest spacers used to set the spur spacing:


Flipped the Losi slipper pad (this one flipped holds the 57t spur in place, the other pad doesn't hold it into place in either orientation, it's easy to tell which one is which)


HR Spur on


Shaved down the other Losi pad so I could have enough thread on the transmission shaft to screw the nut onto. Left is shaved, right is unshaved.


2nd losi pad installed with shaved side up


Nut installed


I used some more of the HR m2 spacers and some washers from the losi micro-t slipper kit to mount the motor


I had to shave down the front driveshaft so it would clear the spur.


If I find any stripped screw hole thread I use these 0-80' thread size and 5/16 inch long socket head cap screws (from mcmaster-carr) to replace the stock screws. They're slightly larger in diameter and so they screw in really snug. I used them on the transmission but they are not needed for anything here. I'll use them for mounting the body panels I'm going to make later on, but I did find that the stock screws actually screw into the holes on the Specter chassis just fine and are close to the recommended screws in length.


A demo of how the tranny will mount onto the specter chassis

 

[noel2]

What's left:
- Using the DXF files for the sub-chassis and body panels to cut and make and my own out of 1/32 aluminum sheet (body panels) and 1/16 delrin for the sub-chassis. My plan is to print the files onto paper, cut out the designs, draw them onto the aluminum/delrin sheet and then make some changes for the SCX24 parts.
- Make custom links: I have some 2-56 brass threaded rod and a set of extra stock scx24 links that I'll use. My plan is to four link the front and use the stock rod-ends (cut and drilled to fit the threaded rod)
- 43mm shock mounts: I bought these used so I don't have any mounting hardware. I'll have to figure these out. I'll most likely moun them off of the sub chassis.
- Sand and paint
- Still need RC4WD beadlocks for the scramblers
- Electronics: I'm not sure if the stock ESC will be able to handle the scramblers, overweights and PN motor. It does good with the stock motor, overweights and the MTRs. Only testing will dictate if it'll hold up. I also have to figure out where to mount the RX/ESC and LiPo on this tight chassis.

 

[Brake Weight]

Awesome project.

 

[MrSquiggles]

Subbed!!!!

 

[noel2]

Subbed!!!!

Awesome project.

Thanks! it'll be a lot of work but it should be entertaining.

 

[1tuffmj]

Cant wait to see your progress

 

[distress]

Awesome project! Fungi has some good stuff as does GamyRC on Shapeways.

 

[noel2]

Awesome project! Fungi has some good stuff as does GamyRC on Shapeways.

Thanks man!

Cant wait to see your progress

I got some work on the specter done yesterday. Sorry about the mess in the background, I got carried away and forgot to clean up before taking pictures.

I used the available DXF files provided by Fungi. They're on the facebook Micro Rock Crawlers group. There's a 1x1" reference square on the files. I used adobe illustrator to scale them to size. Just printed them and cut out the sub chassis to use as a stencil:


I used the stencil and etched the outline onto the 1/16" delrin sheet using an exacto knife. You definitely need 1/16" material as it fits perfectly between holders in the front and rear.


Then I cut two out using a dremel, clamped them together and finished them off so they'd be equal in size.


I taped the stencil onto the sub-chassis and drilled the mounting holes only.


Screwed them in using the required 0-80 thread 5-16" long socket head cap screws (from mcmaster carr). You have to clean the holes on the chassis first using a 1mm drill bit as there's powder left in them from the printing process. If not, there's a risk of cracking the chassis.



The SCX24 transmission fits perfectly! Just need to make custom mounting holes.


Made the mounting holes by just eyeballing and marking the spots where the holes go. I would mark with an exacto-knife the horizontal and vertical location of the screw and wherever the lines met is where I drilled. You can see the lines here:


I also mounted up the axles using the stock links. The front is definitely too long, I'm gonna make shorter links later.


I did a quick flex test. Probably 60-70 degrees of flex, which is pretty solid. I don't think I can switch out the stock link ends since the lower links mount into cutouts in the transmission. Wish axial would have designed them like the losi to mount off of ballstuds. Ballstuds just have way more potential for flex and performance.


Also dry fit the HR shocks. I'll need to figure out a proper way to mount these but they look great, I think I'll end up de-anodizing the ends though. They're a little stiff but that's nothing a spring trim can't fix.


Four stock axial tires and a little bit more of flex.


Next up are custom links using stock link ends and 2-56 threaded rod. Then shock mounts, electronics, making the chassis panels and then painting them up.

 

[Brake Weight]

Nice.

 

[noel2]

Nice.

Thanks! I know it doesn't look great right now, but there's still tons of work left to do. With body panels and the right length high clearance links (shorter up front), it's gonna be perfect. Scramblers should also be a nice touch. Just waiting on RC4WD to get their stock in order.

 

[Thompson311]

I love the way it is coming so far. cant wait to see it all finished

 

[1tuffmj]

Looking great.i did my sub chassis same way.

 

[jimbo74]

Does your servo get warm? Like really warm?

 

[noel2]

Does your servo get warm? Like really warm?

It did for a couple of runs till I set my dual rates properly. It runs good now, super strong, no issues.

 

[noel2]

Looking great.i did my sub chassis same way.

Thanks! It's pretty easy to make the sub-chassis, just need a dremel and the right bits.

I love the way it is coming so far. cant wait to see it all finished

Thank you, I got the links finished today:


I didn't take many pics but here's a quick summary:
I used 2-56 threaded brass rod. About a foot of it. I used stock link ends, just cut the ends off and drilled them with a 1.9mm drill bit. The front upper link ends needed to be shaved down in thickness and I had to drill out the link mounts on the servo plate. I shortened the front lengths about 3/8" and four linked front as well.I used two M2 screws to hold the front upper links in. All the links are bent for high clearance


I did some flex tests and have around 75 degrees of flex with no shocks on:




Now I need to figure out shock mounts and shock mods, which will probably be the hardest thing to do next to cutting out the chassis panels. I also need to work out electronics entails finding smaller batteries. Then sanding and painting. I'm also going to heatshrink the bare threaded rod or else it's going to hang up a lot on obstacles.

BTW the small white blemishes on the top center bar and two hood bars on the chassis are from sanding. I filled in two small holes that weren't meant to be there with super glue as filler.

 

[noel2]

It's been a week since the last update, I got a lot of work done on the SCX24 Specter:

Finished making body panels. I used a sheet of 1/32" thick aluminum. The DXF files are available on the Micro Rock Crawlers Facebook group using the search bar. I had to design my own hood and roof. I used 3/8" long 0-80" threaded screws to mount all of the body panels.

I used heatshrink all of the links since the last update. I need to shorten the front lowers to angle the axle downwards as the servo is hitting the chassis really early. Doing this will allow for more articulation. I dry fit the HR shocks and had no articulation because of this.



There is a 1"x1" reference block which makes it super easy to print the whole file to scale. I did, and then I cut out the panels. The files were shown in an earlier post on this thread.
Here are the cut out side panels and rear panel templates:


Since there are no designs on the DXF files for the hood and roof I instead made my own templates:


Then I drew everything onto the sheet of 1/32" aluminum:


I used metal snips, or tin snips, to cut out all of the panels and then I finished them off with a dremel. I laid the templates on top and drilled out the holes using a 1.6mm drill. They weren't perfectly lined up so I had to open upsome of the holes as you can tell in the pictures if you look closely. It kind of bothers me but it's not too bad and aluminum at this size and thickness is not fun working with when you only have basic hand tools, so I really do not feel inclined to make any new side panels. Here are some pictures of everything fit onto the chassis. The panels are all somewhat sanded by the way. The hood also looks scuffed, but that's because I used some glue as filler since it was really scratched up. I need finish filling and sanding it.







I also picked up these small 300 mAh 45-90c nanotech 2s LiPos that fit perfectly in between the transmission and the SCX24 frame rails.


Some comparison pictures next to the stock 350 mAh, 30C 2s LiPo that has a much larger footprint:




I also de-cased and heatshrink wrapped the ESC, shortened the servo wire and made a proper battery adapter from JST PH2.0 to regular JST connectors. Previously I just had the regular JST plugged into the ESC board without a connector and the pins are not the same size between the two. So I replaced the connector on the board and made an adapter:


Everything fit tightly. ESC is taped to the underside of the roof, upside down. It just barely clears the motor this way. The battery gets pushed in from the side or the rear and can be removed for charging.





Next is sanding, lots of it. I need to get the chassis nice and smooth as well as the panels for some Tamiya primer, then a black base coat and a flat clear coat. It should look great once it's all done.
I also need to figure out shock mounts. I'm going to tilt the servo forward which should hopefully solve the articulation issue. If that doesn't work, I'll need to make a new sub-chassis to mount the shocks from because the mounts on the bars of the specter chassis are centered, and the SCX24 axles aren't meant to have shocks mounted at such a steep angle: articulation is limited. I'll get it worked out though.

 

[bolo79]

I really like raw aluminum look and way is sitting so low.Mean little thing.How much ride hight will change after you install stocks?

 

[noel2]

Up for grabs on eBay:

https://www.ebay.com/itm/233569658317

It's not running and it still needs some work. I never got around to finishing in, just lost interest.