Mini/Micro - MOA - Scratch Build

[MAXXMASHER]

Man, those wheels/tires are great! You do some awesome work!!

[danielk]

to get some rear squat for better climbs you could move your rear uppers down at the chassis side.

your rims look really good. You should first try putting a chamfer on the inside edge of the PVC ring. Also, a taller narrow foam should help make the tire profile taller and skinnier.

[sweli]

Originally Posted by danielk

to get some rear squat for better climbs you could move your rear uppers down at the chassis side.

your rims look really good. You should first try putting a chamfer on the inside edge of the PVC ring. Also, a taller narrow foam should help make the tire profile taller and skinnier.

Thanks for the link info. This is really only the second 4link I have built.
First was a 1.9 Mog scaler. My main rig is a BMV torsion.

You are right on the chamfer on the PVC. Playing around with them, looks like the washer sat down so tight, the PVC edge bit through the bead in a couple spots.

[sweli]

Originally Posted by MAXXMASHER

Man, those wheels/tires are great! You do some awesome work!!

Thx Maxxmasher!

They are actually pretty soft and sticky. I wonder if they are Losi 'blue' material or other. They almost feel vinyl??

I took the wheels back apart. I think I need to take a little off the width of the PVC pipe. And try the chamfer like danielk suggested.
The nylon rings pulled the tire in hard enough to cut through the bead in a couple spots. Glue is drying now.


Ordered two more gearmotors. Went for the 150:1 with 45oz of torque.
Prob here on Tuesday.
I need to fab a thin steel or alum plate to mount them to with the 2mm screws, then I can mount the plate into the gearboxes spaced wider apart with 3mm screws.

Busy weekend, not sure how much time I'll get before Sunday.
More to come...........

[Stormin2u]

Crazy wild and just down right awesome work.

[xSavage25x]

I like what your building. I'll be following along.

[Aussie Nerd]

This build is getting more incredible with each update This is a 'Build' in its truest form. Those beadlocks are a brilliant idea, are they quite heavy with all that lead and putty though?

Kieren

[sweli]

Originally Posted by Aussie Nerd

This build is getting more incredible with each update This is a 'Build' in its truest form. Those beadlocks are a brilliant idea, are they quite heavy with all that lead and putty though?

Kieren

Hey Kieren,
Thx for the comments!
Wheels: 1-3/8 oz
Wheels+rings+6screws: 1-7/8 oz
Wheels+rings+screws+foam+tires: 2-3/8 oz

Sorry, if you wanted grams.

Waiting on new gearmotors, then I need to fab some thin motor plates.
I stripped one mounting hole on the front brass plate (tiny). Drilled and tapped a new hole slightly off-center, but the motor twists under load now.

[sweli]

Got some more pics to show some progress.

• Not a lot of room actually "IN" the chassis, so I fabbed an electronics tray on top. Not good for the COG, I know.
• Full size Novak Synth Rx up front standing on end
• RC18 ESC behind that in the chassis, under the tray
• (2) 250mah 2s 20c Lipos
• Associated/LRP micro ESC (same as RC1

The tray has mitered edges that sit partially in the chassis rails for locating. A single pocketed screw holes it on.
Dual batts and ESCs for no clod stall. Prob is that the mixing actually seems to introduce a little. I think it can be adjusted out.
COG is not the best with the E-tray, but really isn't too bad.

[Duuuuuuuude]

Thats awesome man...looks like fun!

[sweli]

I do not have video to show, but she does crawl.
Up about a 70deg incline on some grippy wood.

With the smaller rear track and front CVD's, steering is pretty good.
Steering servo is plenty strong, even getting fed from one of the ESCs internal BEC.

Speed is great for this scale!

DIG was working, but not well. Front alone seems to be on the weak side pulling the whole rig.
The retapped gearmotor mount on the front motor gave loose during the 3rd dig try. I think this screw had started to strip and went in a little crooked.

New, 150:1 gearmotors came today. Hello torque, but goodbye wheelspeed.
Considering running 18T pinions on frt and Rr versus the 17/16 that is there now. This along with the 150:1 should gain me 20% increase in torque and 20% loss in speed.

Need to mount the gearmotor to an alum plate then into the gearbox to reduce flex under load. The 2mm screws in the delrin slots were giving too much. Thinking of fixed mount to the plate, then 3mm screws in slots in the gearbox to the plate.
The gearbox is getting the swiss-cheese look though.

[myrna]

If I would have these axles I would build a stick crawler. Is easier in construction and climbs often better than most of others.
Wondering why nobody is producing MOAs in this size - but hopefully they will be available one day.

myrna

[sweli]

I thought about doing a stick or torsion rig with this. Would have been easier from a design and fab standpoint, and cost would have been lower. Challenge is finding a stick that would flex yest be a strong enough backbone on this size and weight rig.
Could have gone stick with large endlinks and a shock on each end.

So far the trouble is not the chassis, but the motor mounts. I was impressed with the power it had on a about a 70deg climb up plywood, but then the screws gave.
The delrin front gearbox got a little sloppy. Spur gear axle bearings could have been tighter. And the motor mount mesh slots were a little oversized.

Started cutting a new gearbox tonight. Tried alum at first, but found my 40yr old Sherline Mill and high speed steel end cutters did not like that and chattered.
Back to delrin, but possibly with a thin alum motor plate over the brass gearmotor plate.


Front Gearbox #2 in vise on Mill. Flycutter was throwing shavings everywhere! Alum trial block in front.


Empty/sad front axle.

[sweli]

• Cutting a new front gearbox
• New motor mount idea
  • Alum/Delrin vertical section in place of milled in delrin wall
  • Thicker then normal wall stock
  • Shifted towards pinion gear to bring pinion closer to gearmotor to reduce twist around the mount
  • Wider foot on vertical section to assure it sits flat
  • (2-3) 3mm screws holding vertical section inside of gearbox.
  • Screws will pass through slots in gearbox allowing mesh adjustment from front of gearbox (behind steering servo)

Do not like cutting alum, but may do it in this case be be sure this structure is rigid.
Pass through holes for gearmotor shaft and mounting scews.
Blue dashed openings are 3mm tapped holes.



I forgot I retapped the gearbox mounting holes from 1.6mm to 2mm.
1.6mm!!!??? Into brass!!?!?!

[danielk]

I want one but slightly bigger...I want a 130 powered MOA mini. Whatcha think?

[sweli]

Originally Posted by danielk

I want one but slightly bigger...I want a 130 powered MOA mini. Whatcha think?

Sounds fun and really doable.
Scratch or from various parts?

Losi's 18th scale Dessert truck and buggy uses a 280 size motor.

• Another month or so, there will be parts on Ebay. Grab up a couple of transmissions and CVD sets.
• Lock up the difs.
• Use a 130 or 280 gearmotor to power the transmission.
• Use some RC18 front knuckles.
• Cut 1-2" out of each CVD and weld or joint them back together.
• Fab up a delrin axle to pass under the gearboxes and out to the knucles and rear axle carriers.

Trick would be steering servo mount and how high the upper links would triangulate over the gearbox and motor.
Could spin the front gearbox around, so motor is tucked in between links. Would give more room for a servo on the front.

[sweli]

Milled a new front gearbox.

• Alum "L" machined as I previously posted a sketch of, to hold gearmotor.
• Almost same as old gearbox. Same outter shape.
• Wall removed that gearmotor mounted on.
• Wall remains where spur axle bearing resides.
• Pocket milled for alum motor bracket to sit in.
• Outside dim front to rear increased.
• Slots milled in front face for 3mm panheads to hold alum gear box mount.

....and a comparison to the first gearbox.....



Not sure what I will do in the rear gearbox. I may try to forgo the alum bracket and mount the new 150:1 gearmotor and 18T pinion with the current holes through delrin.
Trick will be getting around the 18T diameter to tighten the screws.

[danielk]

Well, the Losi mini-t has been out for years, so the parts are out there. I could just look around for a couple of them. I think a couple of low-reduction 130 motor gearboxes would be perfect.

[sweli]

Ah...... Micro T tranny would great!
Made to hold a 280.
Get rid of the rear guard and pop a 130 or 12mm gearmotor in there.
Shape is decent too, to mount to a cross-axle.

[danielk]

I don't think a micro-t trans would be big enough to handle a 130...We are talking 140g/cm+ startup torque...