Mini/Micro - MOA - Scratch Build

[sweli]

Got sidetracked and started to waste time on attempting an RC18 beadlock wheel. One is 60%.
Might have pics tomorrow.

[sweli]

Originally Posted by soundcolor

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

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

BTW, what are you building Soundcolor?

[OutlawCrawler]

Man I love to see the talents of so many of our members here, this build is just unreal. Wow just doesn't even cover it .

[MAXXMASHER]

I think I'm doing cool stuff with various builds and I find a thread like this and realize I may as well be playing with legos or something. Your skills are top-notch! This build is just incredible! Nice work. Can't wait to see the finished product!

[sweli]

Wow, thx for the feedback!
I just hope she runs. I'm still concerned about these little gearmotors holding up without bearings, as she is getting to be more like a super version of a micro build (without 4ws).
The pcs are easier to build because of a 10" vertical mill I have on permanent loan to me from my brother-in-law. It is a 30yr old Sherline that runs great.

Batts come today. Going to run dual batts and dual ESCs if I can make it all fit.
Kids have swim class and reports due, so time may be more sparse.

[King of Beers]

Awsome! Love the build! Subscribed!

[5p3ktrum]

Great work

[BEELZEBOB]

Scribed buddy!

keep up the good work

[hitman46mod]

Nice job man.

[dickwart]

interesting... I like it

[sweli]

Thx again for the posts!

Lots of family stuff tonight, but got the links going.
Should have a roller by tomorrow night to show pics of.

Links are 4-40 allthread covered by aircraft guide tubing.
Using Dubro endlinks with brass balls and chamfered spacers. About half of them come out of the package and are stiff. Lube doesn't cut it. the brass has an edge somewhere and needs rubbed with a Scotchpad.
Man I hate stiff balls LOL

[sweli]

Picture is worth 1000 words - she's a roller

• Wheelbase came in at 6-5/8" (little longer then I was hoping for, less and it would not articulate well with these links)
• 4-40 Allthread bent lower links
• 4-40 straight upper links
• Duratrax Cliff Climber Shocks with internal hardware store springs (0.020 dia)
• 2-56 end links on the shock rods
• 70% droop in front, 30% in rear
• Temp wheels/tires (Propulse, ripped when trying to seperate bead to remove foams)

I was shooting for mounting the shocks inward on the chassis, but noooooo room.
Front lower links have good triangulation. Almost too much. I twisted the bend in the link a little outward to compensate and make the end link on the axle pivot better.
Uppers have just enough triangulation to keep it rigid.
Front has fair articulation, rear has great.
Shock springs seem about right for the weight of this.


I think I might need a new motor already. The mounting hole stripped on the one I kept trial fitting during machining of the gearboxes. Drilled an alternate hole next to it and tapped for 2mm. But its location allows the front gearbox to twist on its mount under load.
Might try and removing the brass end plate and tapping the original hole to 3mm. You have to remove it to do this because the little steel gears are right up against the inside of the plate.

[Aussie Nerd]

It has turned out great Can't wait to see some pictures on the rocks. Did you even get anything done on the beadlocks?

Kieren

[sweli]

Sorry, I forgot to lay a ruler in the pics for reference. Next pic will have one in it.
What started as a micro grew to a 'super'(sized) micro, or what I like to call a "Sorta Super Micro".

With the use of a gear motor driving a pinion and spur setup, a lot of the torque is on the gear motor mounts, which happen to be little 2mm screws through thin delrin, into a thin brass plate.
Besides dual ESCs and Batts, I was overdriving the front with a 17T versus 16T pinion.

Hooking up the front motor only and putting some resistance on the rear axle (simulating DIG), I watched the front motor twist on its mount.
It was not enough to unmesh the pinion/spur, but is def something to fix.
These motors have LITTLE solder tabs on them, and after a few torques, my wire lead came unsoldered on it where it rubbed the wall under load.

Twisting, and the front overdriven motor was not fully up to the challenge of dragging locked rear axle on carpet.

I am considering a thin plate (steel or alum) that screws to the brass motor plate, and then offers wider/larger mouting points to the delrin gearbox.
I could try going back to an equal 16T but that only changes it some.

[sweli]

Here are some theoretical calculations for current and possible fixes.

Front Axle - Current:
Transmission Ratio: 100
Spur Tooth Count: 24
Pinion Tooth Count: 17
Total Voltage: 7.4
Motor KV: 5300
Tire Diameter (inches): 2.375
Spur/Pinion Ratio: 1.41 : 1
Total Ratio: 141.17647 : 1
Tire Circumference (inches): 7.46 inches (189.52 mm)
Total Motor Speed: 39220 RPM
Vehicle Speed: 1.96 mph (3.15 km/h)

Rear Axle – Current:
Transmission Ratio: 100
Spur Tooth Count: 24
Pinion Tooth Count: 16
Total Voltage: 7.4
Motor KV: 5300
Tire Diameter (inches): 2.375
Spur/Pinion Ratio: 1.5 : 1
Total Ratio: 150 : 1
Tire Circumference (inches): 7.46 inches (189.52 mm)
Total Motor Speed: 39220 RPM
Vehicle Speed: 1.85 mph (2.97 km/h)


Proposal 1: (new Gearmotors and Pinions)
Transmission Ratio: 150
Spur Tooth Count: 24
Pinion Tooth Count: 19
Total Voltage: 7.4
Motor KV: 5300
Tire Diameter (inches): 2.375
Spur/Pinion Ratio: 1.26 : 1
Total Ratio: 189.47368 : 1
Tire Circumference (inches): 7.46 inches (189.52 mm)
Total Motor Speed: 39220 RPM
Vehicle Speed: 1.46 mph (2.35 km/h)

Proposal 2: (change both spurs & frt pinion)[Not sure how much space I have in the gearbox to go beyond 25T]
Transmission Ratio: 100
Spur Tooth Count: 26
Pinion Tooth Count: 16
Total Voltage: 7.4
Motor KV: 5300
Tire Diameter (inches): 2.375
Spur/Pinion Ratio: 1.63 : 1
Total Ratio: 162.5 : 1
Tire Circumference (inches): 7.46 inches (189.52 mm)
Total Motor Speed: 39220 RPM
Vehicle Speed: 1.71 mph (2.74 km/h)



Pololu gearmotor specs:
Ratio V Rot.Spd Torque
100:1 6v 320rpm 25 in-oz
150:1 6v 200rpm 45 in-oz
Difference: +33% 0 -38% +45%

So is torque a linear relationship with gear ratio?

[BEELZEBOB]

freffin schweet duder!

is that your final chassis, or just a chuck for you to work with?

i bet the lighter you can get that rig, the more badass it will perform!

[sweli]

At work, lunchtime, no rig to tinker with, but cannot stop thinking about it.
So a new level of 'Geek Time' arrives.

Not exactly linear relationships. I think the blip (bumps in the road) are the two points caused by the 150:1 ration gearmotor.

I like the wheel speed this thing might have, but am leaning towards the 150:1 gearmotors + current pinions. See where that lands after electronics are installed and then change pinions up in tooth count for speed.



Torque shown is in inch-oz and is relative to 6v, not 7.4V.

[sweli]

Originally Posted by BEELZEBOB

freffin schweet duder!

is that your final chassis, or just a chuck for you to work with?

i bet the lighter you can get that rig, the more badass it will perform!

Thx!

Electronics are not in it yet. Two RC18 ESCs, two 250mah batts, full size Novak Syth Rx.
She's a-lookin like a top heavy freakshow! LOL

Chassis is pretty lightweight PC blend with the heavier delrin skid down low.

[sweli]

Two beadlocks started.
Functional, but beauty shouldn't be judged.

• RC18 Chrome (almost) flat face
• 1-1/2 PVC drain pipe (schedule30?, thin)
• adhesive backed lead strips
• JB weld
• 1-1/2 (1-15/16) dia nylon washers (thick!)
• 3mm x 16mm panheads

Started by cutting the front face outermost bead rings off. On these wheels with semi-flush fronts, this cut continued to the center hub area.


Then cut the back of the wheel entirely off to a width of 1/2".


Cut the lead strips in half, so they were approx 5/16 wide and wrapped around the wheel. These had to be pulled off a few times and pounded flatter (thinner) with a hammer.
Cut the PVC pipe to just over 1/2" wide and slipped over the lead wrap.
Set them face down on some plastic on the bench, and filled three of the five spoke openings with JB Weld.


When dry, surface sanded the faces back flat.
Pic below, I filled the other three spoke openings half full for weight.
This shows the PVC rings slid back to expose the lead for the pic.
PVC pipe in background.


Three holes in each nylon washer in triangular pattern.
Spokes full of JB Weld are wide enough that two holes can be drilled in each and tapped to 3mm. Three holes for front ring, three for rear.
I used each washer as a template to locate the holes. The are lettered and have a location mark on them.


Front Bead in between wheel and PVC ring.


Rear bead.


Front ring on.

Rear ring on.


The pair.


Not pretty, but functional.
The nylon makes for a durable, slippery face.

[sweli]

Narrowing the wheel width + narrow foam + sipping the edge tread, I thought would make these tires stand taller.

I think the width of the PVC rings versus the wheel width, made the tire bead get pulled around the edge of the rings tightly, keeping a wider stance.

Might pull them apart and try narrowing one of the rings to see the result.

Might only do two of these for now, for the fronts. It will allow weight adjustment.
Rears will get narrowed, one wrap of lead weight (half wide), and glued.