Snap, Crackle, Pop

Soon after fixing the shear pin, we blew up the most highly loaded of the ratchet hubs. The ratchet head itself was fine, it tore out of the housing that I machined.

Several good things here:

A: No damage other than to the hub itself
B: It's easy for me to machine another more substantive hub
C: The propeller was already absorbing almost 2x the design HP before this happened.

All in all an easy fix and under field conditions we don't expect to ever load the system this high again.

Shear pleasure

Our first minor casualty was a shear pin in the prop shaft. The components in this part of the chain are under the most torque load of all. We quickly replaced the soft pin with a harder grade 8 variety and I commented that now we could well break something more expensive. Turns out I was right.

Let's show some restraint here people

Enough excess thrust was generated *after* achieving windspeed, that the dyno was dragged down the parking lot several feet. To keep it in one place, we finally tied it off to the pick truck. The dyno is not on wheels btw, but skids.

This result is completely contrary to the oft quoted theory that no thrust can be generated at windspeed

Uphill, both ways

During some of the testing we loaded up the front of the vehicle and tilted the ramp to force the vehicle to climb as it advanced to the stops. By positioning the stops to start the vehicle axle aft of the dyno axle, the rear wheels were also forced to climb.

The vehicle advances under all conditions.

Before the storm

A few pics from the setup and prep before firing up the wind.

Picture updates to come

In addition to the videos I just posted, I've got pictures as well. I'll get to that after dinner.

JB

Prop shaft break

We moved the pitch to 20 degrees and ran the ratio up to 20/65. First we sheared the grade 2 'butter bolt' that engaged the hex drive to the ratchet hub. We pretty much had the motor maxed out power wise (6.5hp) when that happened so I was hopeful when we replaced that with a grade 8 bolt that we wouldn't break anything else. However before we fired it up this time I said to my buddy Jerry "well, with that soft shear pin gone, now we can break expensive stuff".

It almost came true.You'll see in the video that I fucked up and engaged the idler on the motor drive waaay too fast and I'm sure that's where I blew the side out of the ratchet hub (carnage pics on the blog later). It only lasted a short time and I never got close to max throttle before it blew up.

High speed dyno test

At about 115 rpms and still with the AOA at 15 degrees. Design speed is in the 120 range

First dyno test

This is the first spin up of the cart on the new dyno setup. We were at 15 degrees AOA and were running our slowest gear (15/65). Design point is 20 degrees(tip at static) and 23/65.

Even with the Honda engine nearly idling the vehicle immediately pulled to the front and held against the stops. (for those who aren't up on what that means, it means that the vehicle is going ddwfttw at a very low windspeed -- a good sign of our overall system efficiency).

Pickup work

There were several bits that had been being put aside that we worked on this evening. We made the final thrust box stiffening brackets and installed them. Rick installed the RF board and wired the load cells in the hub and on the chassis. I drilled the prop shaft for a safety pin. We applied Loctite to about a thousand bolts and cap screws. On and on.

Bright and early in the morning we'll be spinning the rig up on the dyno and we'll find out how good or bad we've done both with our drive system and propeller.

DownHonda faster than the Honda

Finished up the dyno mid afternoon. We decided against setting it up outside as the remaining daylight hours just seemed too few. Instead we spent the rest of the day applying loctite and detailing odds and ends that had been put aside.

Dynomight

We fabricated the skeleton of the dyno tonight. I was supposed to pick up the pulley/shaft combo today from the machine shop where is is being lathed, but they were a bit behind and we'll have that in the morning.

All Skate!

From some old roller skates that Rick had around, we threw together a rough guide system for the chain. This will allow us to do the dyno testing this weekend and we'll figure out from that what changes we want to make to the guides.

Ten watts ??

We gave the propeller a quick spin by hand. The odd sound you hear is the ratchet hub as Rick turns back and forth on the rear of the shaft. The "ten watts" comment is an inside joke -- we're quite sure that's a darn conservative number. ;-)

I fold.

Still a lot of work to do, but overall the daylight hours were good to us today. Rick is starting to get pretty happy with the way the telemetry is working out -- he was calibrating load cells today and polishing the code.

This evening I'm going to chop up some tube and flat stock and weld the skeleton of the dyno together. I'll post a view of that in a few hours. Still on schedule to spin the vehicle on the dyno this next weekend. I'm pretty confident we'll get there.

Random shots

Mounting the hub to the stand

This was the first time the prop has been able to spin.

Mounting the blades

Several of the SJSU crew came by this morning and gave me a hand with the trial assembly of the vehicle.

It all hinges on this

Spent the better part of last evening finishing fabricating and installing the hinges and stops for the prop tower pylons. These hinges will allow the tower to fold forward for travel.

It's a long way to the top

No clouds, but the vehicle's got its head in the ceiling insulation.

This evening I'll get the hinges and pins drilled and installed on the pylons. We'll then roll it outside where there is room to put the hub back in and mount the prop. It will be very cool to see it 95% assembled.

Solve the Ridley

The first steps of the vehicle. (And no, Ridley Scott is not just off camera directing -- it actually rained).



This is the approximate pilot position. We'll have a sling seat between the chassis rails but for the pic I was just using my elbows to keep my jeans off the wet pavement.