Boxing is the trick

I finally finished painting the mega axle with two coats of black enamel paint, which included painting inside the cross axle square tube.  Painting inside a tube was an old trick using a sponge and a coat-hanger.  It was messy, but functional.  Now the axle is fully painted and bolted onto the trailer frame.

Moving on to torsion.  I've been disappointed at the low torsional stiffness.  Adding the side-walls was very helpful, but I can stand on the back corner of the frame and see everything flex, including the walls.  I see the main beams twist slightly  One idea was to add more parallel frames beneath the floor (which also doubles up support for the plywood floor).  The last good idea was to add a top lid of trusses.

Some previous experimentation clamping spare angle across the top seemed plausible, but didn't give enough improvement.  Today, I clamped three eight-foot 2x4's as trusses across the open top.  Those were instant magic for increasing the torsional rigidity.  I can literally stand on the back corner and the front of the frame stays stiff.  Amazing.  This finally puts a finger on the right next step.

I took a drive around the neighborhood with the three 2x4's clamped across the top (this was the first real drive with the torsion axles too).  Driving was better, though the long unsupported upper rail on the front was quite wobbly.  After stopping to inspect, one of my original frame welds had broken, which let the vertical strut start to flex.  That's fixable.  It also suggests that adding more cross-frames may help more than I realize, since not having just one weld made such a difference.  Lastly, it also means I really must weld all of the inner joints rather than just the upper flange.  For another day...

Also of note, TIG welding thick aluminum had been getting more frustrating.  At 180A, the tungsten tip was melting (green) or exploding into nodules (blue), which meant re-sharpening the tungsten literally every weld.  After watching several tutorials from the excellent Pacific Arc Tig Welding channel on Youtube, it appeared my AC balance of 30% was too much cleaning action for an air-cooled 3/32" tungsten.  My Weldpro only goes down to 30% balance, so decreasing further was not an option.  After watching several more tutorials, today I finally tried the second idea of increasing the AC frequency.  Going from 60Hz to 120Hz did seem to make a difference, and I was able to weld longer without melting the tungsten tip nearly as much.  Hopefully I can keep experimenting with this trick during finish welding.

Before driving around the neighborhood, I repaired the broken wires on the left tail light.  The road literally ground a hole the plastic, so this LED light is probably fine for a bit, but will die a slow death from corrosion.

Oh!  I'm pretty sure I found a field for a first flight.  Blackstone Army Airfield (KBKT) is uncontrolled on the weekends and has a 5,000ft x 300ft dead runway that is perfect for both driving on and doing a takeoff and landing.  Most airfields are not cool driving a car on their beautifully manicured grass runways (for good reason), or the paved runway is active for general aviation traffic.  According to the airport owner, so long as I have an air-band radio, I should be good to do the maiden flight there.  He has had other ultralights fly from the field, so there is even precedent.  Hopefully this ends the search saga.  It is a three-hour drive to get there, and will be even slower when towing a trailer I do not yet trust to go around the neighborhood.  One day at a time.  At least this is non-zero progress!

Trailer to do's are now:

• paint axle assembly with some enamel paint
• repair left tail-light wiring
  
• buy more Argon gas
  
• finish weld the vertical elements
• epoxy-coat seal the ply decking
• install and wire running lights on the sides
• add reflective tape on the sides
• create a rear door that can be quick-pinned in place
• figure out front/side/back walls
  
• dream up a top lid
• figure out how Goat parts sit in the trailer
  
• take all of Goat for its first trip around the neighborhood 
• be comfortable driving six hours at highway speeds
  

For the first-flight:

• backyard final assembly and thorough pre-flight check, including weight & balance
• re-weld the tow hitch release (I'm now doubtful it had good penetration) 
  
• buy tow rope, weak-links, and end rings
  
• buy/borrow radios (1x airborne, 1x car)
  
• find a place to fly
• travel
• fly

After the first-flight:

• add leather patch to wing tips where will rub the ground
• install leather patch guides for elevator control lines
• paint trim color
• install wing root kiss seal
• build a wing tip dolly
• build a wing wheel
• jury strut fairings
  
• main strut fairings (after flying to figure out the right angles)
• emergency parachute
  
• real variometer (LXNav with a TEK probe is my intention, if it is sensitive at low speed...)
• drogue chute

Painted axle

Just chipping away at an easy task on an unexpected weekend day off, I put a coat of paint on the new axle.  The steel had some light surface rust already starting to grow, so it was time to add protection.

I simply brushed on Rustoleum black semi-gloss enamel paint.  The axle went from looking reasonable to looking awesome.  Paint makes such a difference visually, and I really hope that it protects the metal beneath (expect three coats, and inside the open square tube also).

Trailer to do's are now:

• paint axle assembly with some enamel paint
• repair left tail-light wiring
  
• buy more Argon gas
  
• finish weld the vertical elements
• epoxy-coat seal the ply decking
• install and wire running lights on the sides
• add reflective tape on the sides
• create a rear door that can be quick-pinned in place
• figure out front/side/back walls
  
• dream up a top lid
• figure out how Goat parts sit in the trailer
  
• take all of Goat for its first trip around the neighborhood

For the first-flight:

• backyard final assembly and thorough pre-flight check, including weight & balance
• re-weld the tow hitch release (I'm now doubtful it had good penetration) 
  
• buy tow rope, weak-links, and end rings
  
• buy/borrow radios (1x airborne, 1x car)
  
• find a place to fly
• travel
• fly

After the first-flight:

• add leather patch to wing tips where will rub the ground
• install leather patch guides for elevator control lines
• paint trim color
• install wing root kiss seal
• build a wing tip dolly
• build a wing wheel
• jury strut fairings
  
• main strut fairings (after flying to figure out the right angles)
• emergency parachute
  
• real variometer (LXNav with a TEK probe is my intention, if it is sensitive at low speed...)
• dogue chute

Mega-axle!

The torsion axles are not going anywhere ever again.  The frame is going to bend before this axle dies.

Welding steel is so much more enjoyable than aluminum.  It took about three hours to work my way around all the open edges, but it wasn't that bad.  The arc is more stable and it seems like this is the way welding should be.  I must be doing something wrong with the aluminum setup.

The axle assembly is bolted back to the frame now.

I thought about going for a short drive around the neighborhood, but I've done this before.  One of the aluminum truss members has broken tack welds from yesterday's crash.  Without the ~200b of plywood being bolted back on, the trailer will ride light and bounce around.  I'll save the drive for another day.

Next up is liquid wet stuff.  Enamel paint for the axle.  Epoxy-coat for the plywood decking.  It'll be a few days in the garage, so I might not get to this for a while.

There are some repairs to do from the broken axle event last night.  The left trailer light rode on the asphalt and destroyed the wires and scraped away some plastic.  Ironically, I have a spare left light assembly if this one not repairable.  Some of the metal frame also scraped away and needs inspection.  It never ends.

Trailer to do's are now:

• weld axle assembly
• drill holes in axle assembly
• mount axle assembly
• paint axle assembly with some enamel paint
• repair left tail-light wiring
  
• figure out how Goat parts sit in the trailer
  
• take all of Goat for its first trip around the neighborhood
• buy more Argon gas
  
• finish weld the vertical elements
• add reflective tape on the sides
• install and wire running lights on the sides
• epoxy-coat seal the ply decking
  
• create a rear door that can be quick-pinned in place
• figure out front/side/back walls
  
• dream up a top lid

For the first-flight:

• backyard final assembly and thorough pre-flight check, including weight & balance
• re-weld the tow hitch release (I'm now doubtful it had good penetration) 
  
• buy tow rope, weak-links, and end rings
  
• buy/borrow radios (1x airborne, 1x car)
  
• find a place to fly
• travel
• fly

After the first-flight:

• add leather patch to wing tips where will rub the ground
• install leather patch guides for elevator control lines
• paint trim color
• install wing root kiss seal
• build a wing tip dolly
• build a wing wheel
• jury strut fairings
  
• main strut fairings (after flying to figure out the right angles)
• emergency parachute
  
• real variometer (LXNav with a TEK probe is my intention, if it is sensitive at low speed...)
• dogue chute

Axle, axle, then no axle.

Steel is significantly easier to tack weld.  The welding arc is much more stable and produces a small and stable melt pool.  I tacked together the assembly in just a couple hours.

This is what the axle assembly looks like (the bolt plates are not yet tacked in place, and I missed a picture of those in this view).  It looks similar to the original leaf spring axle assembly, but isn't red.  I'll either see if work can powder-coat, or I'll paint it with enamel paint later.  I did weigh the old axle components at 80lb toatl (30lb axle; 25lb/ea leaf spring, angle, fenders).  The new torsion axle assembly weighs 52lb (22lb as shown below and 15lb/ea for the half-axle assemblies).

Show partially bolted in place in this view, the half-axles transfer load to the bar, which transfers loads to the steel angles, which transfers loads to the main aluminum beams.  The bolts are just there to hold the assembly in place.

 

But, it turns out that the few tack welds did not survive the neighborhood drive.  I was only rolling about 10mph, but the left axle literally broke off and rolled forward while the back corner of the trailer dragged along the ground.  It was quite a noise and one neighbor came over.  Two large c-clamps were enough to hold things together enough to limp home.

What's the saying from the movie Rounders?  "If you can't spot the sucker, then you are the sucker."  Said another way, "I am the crazy neighbor." It's probably more fun to be the crazy neighbor.

Torsion bar for a torsion axle

Steel for the axle assembly arrived today and it fits together as expected.  All I have to do is drill four holes, clean it, align everything nicely, and learn to weld steel.  This may be a weekend project.  I'm hoping to not need to borrow a friend's MIG welder, but that is a backup idea.

Here's what the physical arrangement will look like.  For now, imagine the prettiest welds you've ever seen.

Our of curiosity, I weighed the individual pieces (5.1kg + 2*1.5kg + 2*369g + 2*420g) and get a total of 10kg (22lb) before welding and hardware.  Now we know.

Halfway to a torsion axle

I removed the wheel from the old leaf spring assembly and clamped the new torsion axle in place to get a rough idea of the fitment.  As a starting point, at least the same wheel fits on the new axle.  With zero mounting structure yet, the new axle height is reduced by several inches relative to old.

It took some elbow-grease to remove all of the old axle assembly parts.  Leaf springs are unbelievably heavy, and the old steel axle is itself also crazy heavy.  I've removed probably 100lbs so far, and only maybe half of that weight will go back on.  The new ride height is definitely too low, but it was nifty to see just how low the deck could be.

The torsion axles were simply clamped to an existing cross-member for the time being.  With all of my body weight, the axle appears to move roughly 1/8" in height.  That does not seem very soft yet, though the leaf spring compressed probably 0.0" height.  At this moment, I wish I bought the 550lb set.  They use the same mounting bolt pattern, so perhaps I can exchange this set for the other if it still rides too stiff.

With some scrap steel square tube, I mocked up the structure that will be welded together as an assembly.  This isn't perfectly representative, as one tube will be 2x2 square (vs 1.5x1.5 square shown) and the other will be a 2x2 angle (vs 1.5x1.5 square shown), but was enough of a mockup to feel confident in ordering materials.

Materials are on the way...

Trailer to do's are now:

• bolt the ply decking to the floor
• buy torsion axles
• uninstall leaf spring assembly
• buy torsion axle materials (and associated welding stuff)
• weld axle assembly
• drill holes in axle assembly
• paint axle assembly with some enamel paint
• mount axle assembly for keeps
  
• figure out how Goat parts sit in the trailer
  
• take all of Goat for its first trip around the neighborhood
• finish weld the vertical elements
• add reflective tape on the sides
• install and wire running lights on the sides
• epoxy-coat seal the ply decking
  
• create a rear door that can be quick-pinned in place
• figure out front/side/back walls
  
• dream up a top lid

For the first-flight:

• backyard final assembly and thorough pre-flight check, including weight & balance
• re-weld the tow hitch release (I'm now doubtful it had good penetration) 
  
• buy tow rope, weak-links, and end rings
  
• buy/borrow radios (1x airborne, 1x car)
  
• find a place to fly
• travel
• fly

After the first-flight:

• add leather patch to wing tips where will rub the ground
• install leather patch guides for elevator control lines
• paint trim color
• install wing root kiss seal
• build a wing tip dolly
• build a wing wheel
• jury strut fairings
  
• main strut fairings (after flying to figure out the right angles)
• emergency parachute
  
• real variometer (LXNav with a TEK probe is my intention, if it is sensitive at low speed...)
• dogue chute

Torsion axles arrived

They are quite stiff.  Hopefully this works!  We're going to find out...

We're also going to find out if my welder can TIG steel also.  It does do stick-welding, but that's so messy...