Mini/Micro - MOA - Scratch Build

[sweli]

Almost bought a Losi Micro Crawler, but after hearing what you had to do to make it crawl well and the binding issues, I decided to build what I have thought about for a few months now.

Goal is an MOA, 1:24th scale, comp crawler (not scaler).
So far it is looking like it could be called a super version of a micro 1:24.

Some parts:

• Lots of Delrin through my vertical mill
• Sanyo 12mm gearmotors - 100:1
• RC18 MIP shafts
• RC18 wheels/tires for now
• 4-40 links
• (2) RC18 ESCs
• full size Novak Syth Rx
• Hitec HS-82MG (steering servo)
• '37 Ford Sedan body

[sweli]

Rear Axle / Gearbox

[InFlames]

This should be cool!

[Aussie Nerd]

Wow this is going to be awesome My bet they will change the rules for 1/24th comps so you can't run these because they are so good Can't wait to see some more.

Kieren

[sweli]

Thx for motivation.

The gears are steel on the Sanyo gearmotors, but they are tiiiiiiiiny
Hope they hold up, especially if I can get mixing working on the 3PM for DIG.

Rear axle assembled.
Had to fab a long shaft to move wheels outside of possible shock mounts and body.

[Aussie Nerd]

Looks fairly bulky, do you think that will be a problem? Do you have bearings or does the shaft just run through the delrin? Anyway keep the updates coming.

Kieren

[sweli]

At the end of the gearmotor is a 17T 48P gear, on the axle shaft is a 24T 49P gear.
They are the combined dia necessary to clear half the motor + axle bearing dia.
After fabbing it, I realized that the width of the block could have been narrower. It houses those two larger gears under the cover (along right side of pic), and complete gearmotor on the left.
I could leave the gearmotor hanging out like on 2.2 MOAs, but it is held in place with two, 2mm screws into brass plates. I think it needed protected.

There are 4x8x3 flange bearings holding the axle shaft. I could have gone with 3mm, but had these around from another project.


Front axle is the trick. All this but shorten the solid axle and add stubby RC18 MIP shafts for steering.
I have those shortened and started cutting the axle. Pics soon.

[sweli]

Front Gearbox:

• Front and top outer edges
• Adustable mount for gearmotor (2mm screws)
• 17T pinion, 24t spur (overdrives front, switched rear to 16t pinion)
• Steel shaft through 4mm flange bearings
• Shortened Tamiya steel CV cups (overkill, but what I had laying around)

Back and bottom of gearbox will be the walls of the axle.



Half way through the axle now.
Tricky to think ahead of what I'm cutting to hold gearbox, provide upper and lower pivots for knuckles, link mounts and servo mount.

[sweli]

Front axle:

• Frt Gearbox from post above
• RC18 MIP shafts - shortened, spliced with steel rod and 2mm setscrews into pockets
• RC18 Knuckles - Kingpins are 3mm cap screws with heads turned down. Heads turn in delrin axle parts
• Delrin upper piece acts as servo mount and upper link mouting points
• Upper kinpin mount is black polycarb that wraps around the back

I know, little bulky. Not used to playing with smaller stuff and never said I was a machinist. Wish the bottom had more contour like an axle. Have to see how it does over obstacles.
It is hard to guess how strong pcs need to be in this scale.
Back of axle provides surface for lower link and shock mounting.
Gearbox and axle fit together as a unit and close out most access for dirt into gears.



I will try and get it assembled this afternoon or evening.
3kids and housework are calling.

[badnuz]

this is gona be a interesting build lol.good job mate

[sweli]

Thanks badnuz!
Like to do scratch builds, but never enough time or money to do them 100% the way you picture them in your head.

Forgot to post the sideview of the axle (profile):

Back view (covers gearbox, provides link mounting locations)



Got it assembled now.
FRONT:


TOP/FRONT:


BOTTOM: (had to tuck an unplanned screw in there for strength)



Right-front corner:



Servo really sticks up there, but laying it down would have shifted the top links rearward rendering it not as stable/strong.
If I lay the shocks rearward then the axle could pivot up and roll under.
Body I have planned will end just behind the servo anyway.

[soundcolor]

I'm stealing Your idea, but to use in a completely different way.

One question tho, is the motor replaceable...?

[minisaba]

Wow, every losi micro owner is going to get owned by this crawler. Excellent upcoming crawler.

[madmax22]

This is SICK!

[sweli]

Thx for the comments!

Soundcolor, the gearmotors are for robots. You can get on many sites, I got these at Pololu.
LOTS of sizes and gear ratios are available. One drawback is that these are tiny steel gears on steel shafts that ride in brass endplates with no bearings. The 12mm version I am using uses two, 2mm mounting screws. I am a little afraid of wear.
http://www.pololu.com/catalog/category/51

Not sure if these from Banebots are more beefy. They are a bit longer motors and enclosed planetary or spur gearboxes.
http://banebots.com/c/MS-16XXX-050

On the axle above, the wheel/tire would rub if the motor was any longer.

I wondered about using 'crown' spur and pinion gears from a 1:24 Slot Car axle, so I could mount the motor perpendicular to the axle to give more space and mounting options.

For a real micro, you could use HO train gears and motors.

I wondered what you could do with two Micro-T gearboxes, with a 35:1 version of my gearmotor powering it. Then use full length Micro-T CVD's down to knuckles. Then you would be in the 1:32 range of scale.
Not sure the gear motor would clear the tires on that though. You can get some nice alum versions of the gearbox. I think someone could do up a losi Micro scale with Micro-T gearbox as a transfer case. I wonder if it would hold up to 1:24 scale punishment.

Always do that on the next build. Family only puts up with so much time in my shop before they complain. I am reaching the limit on this one the last few weeks. I taught my son to use the mil for his Pinewood Derby car. A bit safer then the band or scroll saws.

[Duuuuuuuude]

Very nice! Definately subscribing to this one.

[Captaincrash]

Very cool!

[sweli]

Just this summer I tried the WD40 trick on some old Rock Claws and it worked great.

I had some pre-glued Propulse (RC18 knockoff) spike tires on rims.
Heated up and got the inner bead open and removed the foam.
Wow are these cheap tires. The began to tear and peel from handling, which should have been my first clue.

I figured if WD40 on the outside softened, then why not spray them inside and out while the bead is removed and let them sit overnight.

They are a bit softer, but the loose, inside bead is not 1/8 or more, larger in diameter and does not fit the rim!?!?!
The tire material sucked up the petroleum and swelled.

I washed and let them dry. I'll see if the swelling comes down.


I have a set of soft Mini-T Pins that I might use. The are larger bead dia, so I may be jumping in to make some RC18 sized beadlocks.

Anyone know if Mini-T wheels will fit on RC18 stub axles or are they sloppy??


Losi makes some fairly soft 'Smashers' for the Mini-T that might work if narrowed.


They make a Zombie too, but I cannot find anything out on the hardness of them.

[VredenCrew]

The rear wheels from a Mini T will work fine on RC18 stubs. The front wheels from a Mini T will not work as the Mini T is 2wd. Great build by the way.

[sweli]

Knocked out a chassis today.

• Delrin Skid - notched for 4-40 monster links
• Black Polycarb side panels
• 4-40 allthread through the sides, spacers, links, bevels, skid+++

Tried alum tubing for spacers (pics) outside of the links, but proved weak.
Links only come with one bevel spacer, really needs two.
Ended up tightening two 4-40 nuts on some all thread with one hanging over the end a little. Chucked them in a hand drill and spun it slow while filing the end to a bevel.
Now there are bevel spacers on the inside of the links and bevel nuts outside.