Jet Engine - Part 7

This morning I painted and cured the exhaust scroll after grinding off a few spatters and bumps, and filing the flange flat. It turned out reasonably well considering how pitted the original part was.

Then it was assembly time. There's really no secret to this: all the parts go together one way only, except for the shield under the turbine. At first I thought it should cup away from the base of the turbine, since that seemed to match the existing curve better. But after assembling the core I heard the shield rattling around. A quick Internet search showed it should be mounted the other way, curving towards the turbine. This made for a snug fit. The photo shows the correct orientation.

I should mention that it is a good idea to replace the retainer ring on the shaft under the turbine. Since the old one was a pain to remove it was tempting to avoid this step, but under was some coked oil that needed to be carefully scraped out with a dental pick. Cleaning up little details like this can make the different between having the seals last (because of lower friction and the ability for cooling oil to get in there), or blowing them out fast.

A few drops of oil on the shaft and it all slid together beautifully. There were two circle clips in the rebuild kit and I'm not entirely sure what they're for. One could be a replacement for the expansion ring at the bottom of the core, to prevent the brass journal bearing from falling out the bottom. Since there are two replacement journal bearings, it's probably a new clip for each. I just left the original clip in place since it seemed fine. It is unlikely to fail and would be really hard to remove anyway since it's a coil-style and not a circle-clip with ears for a tool.

Admittedly, the washers to hold on the turbine scroll look a little hokey. The originals are too corroded to reuse and are an unusually thick material. I'll have to look for some decent replacements. The seal on the turbine scroll is my main concern with this turbo. I'm not sure how gas-tight it'll be. It wouldn't be good for hot combustor gases to blow out around the perimeter.

The shaft spins nicely and nothing seems to be interfering, so I think things are good to go to the next step: designing and fabricating the combustor. Before I can start that, I need to finish my thermo calculations and come up with a design spec. There are some online tools to help locate the air holes for optimal flow of shield air and combustion air. However, some experimentation will be required before I'm confident to attach the combustor to the turbo.

As you can see, I've rotated the compressor outlet so it's pointing the same way as the turbine inlet. The combustor will mount to the flange I welded to the turbine inlet, and a U-shaped hose will connect the combustor inlet to the compressor. It's looking pretty industrial already and I need to start thinking about how to make this look steampunk with appropriate details for the overall assembly. Lots of brass and stained oak, I think.

Update (April 4, 2014): Work and the need for a MIG welder have delayed my progress. But I promise: more to come!

Jet Engine - Part 6

Welded the flange this morning. Well, actually, Chris Branje (John Branje's son) stick-welded it for me. He earned a case of Bud for his mighty fine job. Check it out:

The procedure was to pre-heat the parts to 800F in the kiln, giving them a good soak before welding. Chris used a nickel flux rod for filler, laying down a remarkably nice fillet. Penetration looked good all around except deep in the scroll crevice where it was hard to reach. We decided to flip the scroll over and just fill that entire area with rod to ensure a gas-tight fit for the flange. The inside of the flange was perfectly aligned and no cleanup there is needed. 

Thanks to the preheating, Chris said the welding was like butter. He's successfully welded cast iron before, but this was the easiest he's seen yet. 

After welding he peened the welds lightly to knock off the dross and I stuck the whole shebang back into the kiln. After re-heating to 800F, I let it cool slowly to about 160F over 6 hours. No cracking observed in the finished product. Oxidation is mild and cleans up easily with a wire wheel on the Dremel. After a thorough cleaning, I'll paint it with the black VHT paint and fire it again in the kiln. 

After Chris finished he let me have a go welding some scrap steel. I had a hard time sparking it up and not getting the rod to stick, never mind dragging a puddle and actually welding. This was my first time trying stick welding. Gives me all the more respect for skilled welders! Hopefully I have better luck with a MIG. 

Jet Engine - Part 5

Time to test that Very High Temperature paint. It's actually a ceramic material, although you need a microscope to read that detail on the label. Prep was pretty straightforward: thorough cleaning with degreaser and water to rinse out all the sandblasting dust, then quick shot of WD40 to displace the water, then another degrease with acetone and then a quick shot of compressed degreaser. The parts came out nice and clean after that, with no apparent oxidation even on the cast iron. You can see why it's called gray iron. Compare the appearance of these parts now with the rusted and filthy junk at the start!

Then it was time to mask and spray. I chose black for the hot turbine parts and red for the compressor. There's not much choice in this temperature range anyway, and these colors should look suitably Victorian. Two light coats and then one medium coat all done within the recommended one hour max, and then into the kiln for a three stage cure at 250, 400, and 600F with a 30 minute soak and cool down between each heat. That red sure looks bright right after painting.

I put the cast iron turbo core and the compressor cover plate under a kiln shelf so it wouldn't be exposed to direct heat from the elements and the little bit of crap that comes off the elements as they expand and contract. I was also curious to see how direct and indirect heating would affect the paint cure. The next morning showed an interesting contrast: the scroll cover which was under the shelf was a nice bright red (although not as bright before curing), whereas the scroll case left exposed to the direct heat was a dull red. Either the direct heat did what it should, or the indirect heat did what it should--but one of them isn't quite right. Thumbnail scratch tests of the three parts showed that the paint is more fragile than I anticipated. Oh well, we'll see what happens when it's really cooking. Hopefully it slows down the oxidation at least a little bit.

The turbo core also took on a blue sheen from surface oxidation due to prolonged heating. Not sure why it would've been so hot for so long: I double-checked my kiln program, but maybe my ramp-down rates were too low. Anyway, this oxidation is cosmetic and should have no impact on the turbo performance since the moving bits are supported by the bronze bearing and an oil film, and there's nothing left to flake off.

Next step was to rig a method of holding the flange to the turbine scroll for welding. I used a scrap of 1/4" plate for a base and then wired everything in place, engraving a groove around the scroll case where it contacts the flange so I can relocate it precisely in case something moves. John Branje, our local expert welder, will attempt to MIG these pieces together using a nickel filler and by peening the welds between passes. Before that I will pre-heat the parts to about 800F in the kiln so there's less risk of heat shock (which can crack the iron casting or weld), and then post-weld slowly cool the parts in the kiln for the same reason. As you can see from my set-up, it'll be easy to lift the parts out of the kiln and onto a ceramic fibre sheet using a long steel rod inserted through the scroll case. One of the benefits of working with kiln-formed glass is I have refractory materials just lying around!

If it all holds together, I'll clean up and paint the scroll case black as well.

The turbo rebuild kit arrived today. All the parts appear to be of high quality and fit perfectly. As a bonus, the replacement o-rings smell like cinnamon oil. Given the kit cost only $78 delivered from Amazon, I should've bought it long ago and just moved on with the project. It's exciting to see this crappy old turbo start to show some promise here! Fingers crossed that by the end of the weekend I can have it all back together and ready to plumb for oil pressure. Then the project really begins.

   

Almonte Riverside Trail now open to Mill of Kintail

After complaining about the dismal singletrack options in the Ottawa area in 2010, I got busy solving the problem and am happy to say that there's now 8km of new trail from Almonte to the Mill of Kintail. The main trail (flagged blue) is about 7km one way, and there's a 700m loop (flagged green) in the middle which goes down to a picturesque set of rapids on the Mississippi River. After cutting the first 4km by myself, local rider Phil Maier did a ton of work to help clear and bench the final stretch to Mill of Kintail. There's now a growing group of local hikers and bikers who use the trail every day.

What next? Well, the plan is to extend the trail all the way to Mt. Pakenham and build a trail centre there. This will require the cooperation of many additional landowners and will take at least a few more years. But having the first phase complete is a big milestone and a great local option.

We are also in discussions with the Mill of Kintail to revamp and open their existing trail network to allow (at least partially) mountain biking.

Group rides are typically Thursday nights at 7:00 pm, starting at the Strathburn St. trailhead. Yes, we ride at night, and we also ride all winter. Fat bikes strongly recommended in the shoulder season and on snow. If you walk on the trail, please use snowshoes so you don't create dangerous postholes for other trail users. Skiing is not recommended because the dense bush prevents good snow coverage over many sections.

Jet Engine - Part 4

Over the last few weeks I've done a pile of work on my jet engine project. It's been on the back burner (afterburner? haha!) for the last few months while I focused on riding, the Wilbur Mine project, and work--which pays for the fun stuff.

Unfortunately, most of the work I've been doing is math: calculating all the thermodynamic transfers from the compressor to combustor to turbine, so I could determine the design requirements for the combustor and develop a fuel injection system. This exercise proved to be quite challenging since it's been about 20 years since my last thermo class, and many important details for the parts I have and system I want to design had to be deduced from a pile of measurements, web info, and educated guesses. I'm not going to go into all the details here just now. For one thing, this blog lacks an equation editor; for another, it would be more useful if I proved out my assumptions before going to all the effort of showing my work.

For now I will say that I found an extremely useful paper from an MIT engineering student who went through the same design exercise as a 4th year project. However, that design used a different turbo than mine and adopted a propane fuel source. Since I want to use kerosene, I needed to recalculate the entire design starting from a different chemical (combustion) reaction, and using a different performance map for my turbo (a Garrett VNT-15 from a VW TDI). The operative concept is calculating the enthalpy of reactants and products through the three stages of compressor, combustor and turbine.

I've completed the calculations and come up with a preliminary design spec. The next step is to design the combustor itself, now that I know the required fuel flow, input and output temperatures, and mass air flow through for my desired operating point.

Meanwhile, I took a break from the math and got my hands dirty. Machining a new main shaft journal bearing has been a real nuisance. I successfully made most of the part to 0.0001" tolerance compared to the original, then took it to a machine shop to bore out the critical internal diameter which includes two steps (the bearing surface) and a recessed area to allow pressurized oil to reach the bearing surfaces. I was unable to make a boring tool fine enough to cut the inside to the required profile, and was reluctant to buy the required tool for about $250. Hence the machine shop. But they screwed up the diameter so now the whole part is junk. Even if I got the interior right (which I'm confident I could), there was the other problem of how to machine an offset circle in one end to accommodate the anti-rotation plug. That would've required a 9mm end mill plus a way to mount it and the part for machining. All told, I was looking at several hundred dollars of tooling.

The easy solution was to order a bearing rebuild kit, which I did for $78 from Amazon. This proved essential anyway, because when I dry-fitted the turbo with my junked new bearing, I discovered that one of the thrust bearings needs to be replaced as well. Plus there's a redesigned oil plate cover in the rebuild kit which is supposed to improve cooling. Bottom line is the kit should solve a bunch of problems and let me move on to more fun things. It arrives next week.

Today's job was sand-blasting all the cast components to remove rust and prep them for painting with Very High Temperature paint. This paint is good to about 2500F and will be applied to all the hot components to prevent further oxidation. The paint is really a ceramic material that sprays on and must be cured at high temperature. Fortunately I now have my glass kiln up and running, so I can cure the paint to 1700F if necessary, which is well above the anticipated ~1100F operating temperature I expect from the jet engine. As you can see, the clean cast iron looks quite different from the crusty lump I started with. This turbo is is in really poor condition--lots of surface corrosion which has eaten away substantial metal--but it should hold together OK. The important bits are there and it doesn't need to take further abuse from a car engine.

The next step was to fabricate a flange for turbine inlet to which I can attach the combustor. This is going to be a tricky operation and it may well fail: I need to weld the mild steel flange to the cast iron turbine housing. It is metallurgically possible to weld cast iron to steel using a nickel filler, but the challenge is keeping everything at the same temperature so the iron or weld don't crack. Cast iron contains a lot of carbon compared to mild steel, which makes it brittle. This problem is exacerbated by the grungy iron of the turbo, which has been soaking up even more carbon from the hot exhaust. The trick will be to heat everything to the same temperature in my kiln before MIG welding it, peening the weld periodically to remove stresses, then cooling the whole welded assembly slowly. This will be a task for John Branje, my local welding expert, who offered to perform the delicate operation for me in my shop.

The flange was cut from 1/4" plate using a combination of angle grinder, jigsaw, and drilling according to a template I made based on the inlet shape. Lots of filing later, it ended up looking pretty good. It'll be important to clean everything before welding, because any contaminants could reduce the ability to weld. I also bevelled the outer edge of the casting to 45 degrees to allow a bit more penetration for the weld bead. Not sure how easy it'll be to get a MIG in there.

Tomorrow I'm going to try painting the all the turbo housing components except for the turbine scroll, which I'll do after it's welded and cleaned up. Fingers crossed that I can pull this off! Otherwise I'm back to square one on this project, and will have to look for a different turbo design.

Wilbur mine update - fieldwork photos

A rare window of good weather on Sunday was all the reason I needed to get out to the Wilbur Mine and start mapping the features in more details than has previously been possible. If you haven't read my previous updates on this project, documenting the history of the Wilbur Iron Mine near Lavant Station (which faded into the bush a century ago) has been a pet research project of mine for the past few years.

Last week I went to the National Aerial Photography Library (NAPL) in Ottawa and scoured the archives for old photos of the mine site. The earliest photo they had of the site was from 1934. It shows a completely different view of the area. Although the mine closed around 1912, by 1934 some key reference points remained uncovered by vegetation or flooded by beaver dams. In Illustrator I was able to scale superimpose the photo onto a map of the mine workings that I traced from a scan of a 1901 original, to create a home-brew GIS with multiple layers of detail. It was fascinating when the two pictures finally aligned and revealed insights I hadn't expected.

Armed with this new map, on Sunday I met up with Marc, one of the property owners at the mine site, to scout through the bush and locate key mine features. Some of these I'd seen before thanks to Bud Thomas (whose mother was a housekeeper at the mine), but Marc's enthusiasm for the subject and knowledge of his property were invaluable help. Below are some of the points of interest. A century of neglect has left many of these ruins unrecognizable to the uninformed eye.

There were 8 workings at the mine site, with #3 and #7 the main points of ore extraction with permanent mechanical installations. The first sign of #7 is a large tailings dump that is clearly out of place in the local features.

On a little ridge near the dump can be seen random iron fixed into the bedrock. This eyelet was probably used to attach a rope or guy-wire to the system for lifting ore out of the working face. 

Just over the ridge is a pond. Closer inspection reveals the rails which led down to the working face of #7 where ore was extracted. These rails were likely supported by a square timber structure which has long since collapsed. Some of the longer timbers could be seen poking up out of the water. 

Past the tailings dump of workings 7 is the K&P rail spur which branched off the main K&P line at nearby Wilbur. The spur follows a long arc around the main mine site, with a second dedicated siding coming back to Workings 3, the largest of the mine operations. The rail bed has severely eroded in many places, especially where it passes near a stream, but clean rock cuts along the sides give it away.

Just past the end of the ridge at workings 7 is the remains of a stone building which the old map suggests was a smithy. Tools for drilling the rock would need to be sharpened and reforged frequently, making a nearby smithy essential. In line with the rails emerging from the flooded face were also some concrete pier bases, likely to supported a system for removing tailings to the dump and ore to cars waiting on the nearby spur.

One of the smaller workings (not numbered on the 1901 map) is this tunnel near workings 7. Bud told me a neighbour used it to store venison. The original tunnel was about 50' long and ended in a shaft which is now just a sunken pit. A series of narrow open cuts zigzag around the area, suggesting the workings were created to determine the location and orientation of the ore strike.  

A fair distance away is workings 3. this was the largest at the Wilbur mine and had extensive tailings dumps which are now completely overgrown. Only the occasional loose rock on the ground, conspicuously fractured and missing moss, hinted at what once happened here. The face of workings 3 is at the treeline and extends underground for about 300' with several tunnels and shafts. It's all flooded now, thanks to the beavers and lack of pumping. Unflooding it would be quite an undertaking. 

Here's an shaft above workings 7. Marc thinks it was a ventilation shaft and that makes sense. There was very little ruble around it, suggesting it was first drilled then blasted with waste material removed from below. 

The K&P spur off the main line passed by this weigh scale now well hidden by brush and blow-down. This was located near workings 7, across a large beaver pond. A squared timber that may have been used in the weigh scale lay nearby.

Here's where the old road to Lavant disappears into the bush. Bud used to plow this road in the winter many years ago. Now the road tends to flood in one section in the spring, and it has been made redundant by a newer road higher up.

Finally, this appears to be the foundation of an old rooming house for mine workers, located where the old Lavant Rd. heads into the bush. This may have been where Bud's mother worked; I'll have to ask him.

This is just a sample of some of the features we saw at the old site. I'll be returning soon to take more pictures and GPS points of these features. These will be overlaid on my map to see how they align with the records. Comparing notes with Marc, it's clear that not all the features are shown on my 1901 maps, suggesting that new buildings were erected and the mine workings were extended after 1901.

If you want to learn more, I'll be giving a lecture on the project in February.

Tatlock marble quarry geology

My post in 2009 about the Tatlock Quarry has garnered more page views than anything else on this blog, so I thought I'd post an addendum with some details about the unusual geology of Lanark County indicated by the quarry. While it's not exactly "dualsport" material, I figure  what the heck. Knowing what you're riding on and through can make any trip far more interesting. Besides, since there are two main geological features that distinguish the Lanark County area, we can pretend for a moment that this is the "dualrock diary". A big thanks to Dr. Paul Keddy's booklet "Earth, Water, Fire: An Ecological Profile of Lanark County" for great insights on the topic.

Geologically, Lanark County is basically distinguished by limestone bedrock in the east and south (think of the Burntlands area just east of Almonte) and Precambrian Shield in the west and north (Mt. Pakenham to Lanark Highlands to Muskoka and beyond). The line between the two regions is visible all the way from Champlain Lookout in Gatineau Park: on the horizon you can make out where the Shield rises from the limestone plain just west of Almonte and forms a ridge running up to Pakenham where the ski hill is located. Behind in the distance is the highlands region. Of course, this is only part of the boundary between the geologies but it's a pretty obvious one to see and a good place to start.

What's also interesting about this ridge is it was the far shore of the Champlain Sea that filled the Ottawa Valley after the last ice age melted around 12,000 years ago. Where previously there was some 3km of ice stacked onto the Valley, all of a sudden (geologically speaking) there was a vast inland sea connected to the Atlantic via the St. Lawrence valley. Vestiges of former beach areas, raw material created by glacial erosion and now marked by large sandy ridges areas along roads such as the Old Perth Road out of Almonte, can be seen today. Imagine seals, walruses, gulls, and other wildlife basking on these ridges the next time you're motoring down this dirt road!

What does all this have to do with the Tatlock Quarry? Well, the boundary between the shield and limestone bedrock regions is rife with protruding marble formations that resulted from ancient geological processes metamorphosing limestone beds through heat and pressure. You can see the bedding layers of the marble in cross-section at the Tatlock Quarry. Striations and darker bands clearly show how the original limestone layers were gently folded and thrust upward as they transformed into marble over time.

Much of the marble in Lanark County seems to be highly granular and poorly consolidated compared to the fine-grained white marbles from places such as Cararra in Italy. You're going to have a bad time trying to carve an old-world masterpiece from a Tatlock Quarry block. I know a few local stone carvers who've had some success with the odd bit of marble found in the area, but for the most part it seems the main value of the deposits is industrial use. For instance, Omya operates the Tatlock Quarry (and others) to obtain high quality white filler use in paints, plastics, and toothpaste.

Fortunately the marble plays a more important role in Lanark County. First, consider that in the areas of Canadian Shield, soils are thin and acidic. Pine trees love this kind of ecology and, coupled with the relatively warm climate of eastern Ontario and easy water access, it's no surprise that Lanark County was once one of (if not the) richest sources of squared pine logs in North America. In fact, Lanark and surrounding counties supplied some 12 billion squared timber logs that were floated down the Ottawa River and sent back to Great Britain and Europe since the early 1800s. (To be even geekier, it was a lumber baron dispute in Lanark County that eventually led to a law that opened up all Canadian navigable waterways to public access. Previously they were private property and you couldn't simply drop your canoe in and fish for perch.)

Second, consider that the limestone bedrock is practically the opposite of the Shield's granite and gneiss geology. Limestone soils are more alkaline and host an entirely different ecology. For instance, the Burntlands alvar just outside Almonte is host to to rare and unique species found nowhere else. That's why we don't ride our dualsports in the area--it has significant scientific value and we need to protect it.

All those marble deposits play the important role of moderator in the midst of all that hostile Shield. It provides an oasis of more fertile, alkaline soils and resistance to acid rain that together allow more diverse types of forest and healthier wetlands to exist within the Shield regions. The marble areas  provide valuable environments for different fauna to thrive where otherwise they would have a much more tenuous existence. 

The marble areas also give rise to some interesting geological footnotes that result in significant rich deposits of valuable minerals--including iron and silver-bearing ores--to form. One such boundary area gave rise to the banded iron deposits that attracted the Wilbur Mine operation near Lavant Station in the late 1800's. Just up the K&P rail bed from Wilbur, near Flower Station, was a significant deposit of silver. Many other mines and exploratory digs existed in the area. Who knew there was so much mining activity here so long ago?

In summary, Tatlock Quarry can be thought of as a highly visible signpost pointing to many other, lesser known but interesting aspects of Lanark County geology and history. It's discovering and learning about these hidden treasures that keeps me rolling on knobbies out in the bush, putting faces to all those names.

Update August 25, 2014: The quarry is closed to public access. According to the sign barricading the road, apparently some people didn't respect the fence, and trespassed into the quarry.

Update October 5, 2015: Seems like the quarry road is open again, although I haven't confirmed it myself.

  

Almonte Riverside Trail - trail work days

On Sunday I cleared and pin-flagged another hundred metres or so of single-track extension to our local trail project. We are planning some volunteer trail work days over the next few weeks (and probably on Sunday or Monday of the Labour Day weekend) to continue clearing and start hand-benching the tread.

It's hard work rewarded by the joy of mountain biking a flowy trail through beautiful forest and hidden ravines along the Mississippi River, and the prospect of a cold beer afterward.

Check out the forum on AlmonteOutdoors.ca for more info.

RotopaX rack with tail bag fabrication

Having an extra 3.8L of fuel on the rack has already proven handy, but the pack and mount preclude  using my shiny new tail bag.

The solution was fabricate a nifty swing-out rack to cover the RotopaX and provide a solid base on which to re-mount the tail bag using the original clips I made. The piggy-back rack (piggy-rack?) is made from leftover stainless steel from our old dishwasher fascia (I've gotten a lot of mileage--literally and figuratively--out of this scrap!) and the aluminum bottom plate from what was once the fastest optical networking switch in the world--a $250,000 circuit board that I can't bring myself to throw away. Poetic afterlife for both abandoned appliances.

An important design goal was to keep things really simple: no weird parts; simple construction that can be fixed anywhere with any available hardware, metal and tools; quickly openable to access the RotopaX; and quickly removable altogether without any special tools. After a few minutes of doodling I had a concept, took some measurements, and got busy.

First I made the top plate from the 1/16" circuit board aluminum. I wasn't really thinking this part through: I just traced the original rack and located where the RotopaX mount would potentially stick through. In retrospect, a plain rectangle would work better and the hole was unnecessary.

Now I needed some standoff hinges and this is where the stainless steel came in. From strips sheared by hand, I used a 3/16" steel rod as a mandrel (and future hinge pin) to bend a tab and form the main hinge body. While it looks tricky (the first one was educational), I was able to make three more in about 15 minutes each. All the bending was done in a bench vise by hand and using a ball peen hammer to tap clean edges. Note that the hinges lack cut-outs for the other half; these will be cut later. 

Holes were then drilled through to secure the flap with two aluminum pop-rivets. Although bolts would be stronger, I didn't have any in a convenient size. Pop rivets would be plenty strong enough in this application and there's no risk of something coming loose. In the unlikely event that a rivet fails, it can be dug out with a Swiss Army knife and replaced with any small bolt or even twisted wire or a zip tie.

Dry-fitting the four standoff hinges around the bottom rack and RotopaX revealed a fitment error. I'd aimed for a 1/4" clearance between the top of the pack and the underside of the top plate to allow for manufacturing variations of the packs and distortion from fuel expansion. However, I'd bent all four standoffs precisely at the wrong location. The top plate was too tight on the pack as a result. Oops. Rather than make new hinges, I was able to heat the bends red hot in a propane torch and then gently forge them flat on my anvil. Other than some minor oxidation, this removed most evidence of my blunder while relieving the metal of any work hardening stresses that would likely lead to cracking under road vibration. 

It was then easy to re-bend the hinges in the correct location to get the right standoff height. Fortunately I'd left long enough tails to make this possible! The lesson is to not trim until you're sure about the fit.

Now to make the other halves of the hinges. This was done in much the same manner as the standoffs, using the same 3/16" rod as a mandrel and trimming the final size only once the bending was complete. By this time I was getting the hang of mandrel bending and it only took a few minutes to make each piece. It's important to file the edges square or the next step won't be precise. 

A vague memory of traditional blacksmithing techniques guided the step of scribing and cutting the standoffs to accept the centre hinge pieces. First I cut slots through the barrel with a hacksaw, then I used a Dremel cut-off wheel to slice along the hinge axis and pop out the centre section. Some filework cleaned up the cut and gave a precise fit with just enough play to allow the hinge rod to slide easily. 

Next was dry fitting and drilling hole locations. Unfortunately, my intended locations for the rear hinges wouldn't work because of the large holes cut into the 6mm bottom rack (that's something to fix in v2!). I  had to move them to an inelegant location. I also debated whether or not the hinges should mount to the tops or undersides of the bottom and top rack plates for mechanical durability. For the bottom rack, I decided that having the hinge hidden away as much as possible would reduce the risk of catching it on something. This is also why I decided to mount the centre portion of each hinge permanently on the rack: it was the least intrusive component. They were attached to the 6mm plate with 6-32 machine screws tapped right into the aluminum. The tops of the standoffs were bolted to the 1/16" aluminum top plate with M4 bolts and nyloc nuts.

Eventually I'll replace all the hardware with one standard metric equivalent (probably M4), and rather than use tapped holes for the bottom hinge, opt for a countersunk bolt from above. Again, keeping it simple and standard makes it easier to fix on the trail with simple tools and common parts.

The hinge pins were cut from the 3/16" steel rod. The ends were rounded into smooth bullet shapes on the grinder to facilitate insertion through the hinges. A small hole was carefully drilled through each end to allow for  a safety-pin style retaining clip (which I may wire to the hinge so it can't get lost). This would prevent the pins from vibrating out of the hinges. Both side assemblies are identical and the rack can swing either way by simply sliding out the appropriate hinge pin.

Here's the piggy-rack mounted on the WR. It's really fast and easy to open and close--no tools required!  The whole thing weighs practically nothing. The hinge pins are the heaviest components. 

I was initially skeptical that using such light gauge material would result in a durable design. However, it's surprisingly sturdy and immovable when you consider that the RotopaX itself bears most of the load via the blue pads I made from some old closed-cell sleeping pad material. I intend to make these pads bigger to improve load distribution. Keep in mind that the rear subframe is only rated to about 15 lbs, so it's not like you need to strap a goat on there (unless it's a small one).

Here's the finished assembly. I reused the original stainless steel clips I made for the tail bag straps, bending them higher and slipping a small length of split vinyl tubing over the sharp inside edge to reduce the risk of slicing through the Velcro. This is OK for now, but a sewn buckle system would be more secure and faster to remove.

Overall I'm pretty pleased with how this turned out although getting on and off my bike now requires some acrobatics. As a test mule, the rack really needs to be flogged in the field to see how well it works in practice. Already I have a list of improvements to the base rack, standoffs, and piggy-rack that I may incorporate into a commercial version that can be adapted to different motorbikes. Would you buy such a product? How much would you pay? I'd appreciate your thoughts on that.

Update (April 4, 2014)

Update October 5, 2014

This crude top rack has proven surprisingly durable despite overloading and trail abuse. However, the sideways flip is awkward to manage when the bag is full, so it's time to think about a redesign. Next version may flip forward, so the bag is supported by the seat when accessing the RotoPax. I may also widen the rear rack to provide better access to the side slots for bungie hooks (currently covered by the RotoPax) and room to rig a mount for soft side bags. There's a TIG welder in my near future which should also help me progress my jet engine project.

Icon Variant helmet review

Few helmet options seem to be available for people whose melons are longer front-to-back, rather than the mythical spheroid shape that 5 year-olds try to draw. My Nolan 102 was aimed at the latter head shape and never really fit me right. Besides creating an uncomfortable pressure point on my forehead, it attracted the mocking of my dear children who likened me to a Playmobil figurine.

Since the Nolan was more than five years old, it was also time to replace it for safety's sake.

None of the convertible options I looked into (including the latest Nolan and Schuberth) fit me very well. Besides, a DS-oriented helmet suggested better ventilation and lower weight at the expense of convertible convenience. Attactive DS options from Arai (XD4) and Shoei (Hornet DS) fit my Nordic head shape rather well. However, they were out of my price range. Also, given the typically low speeds at which I travel and my industry knowledge of helmet testing, I couldn't see a good justification for the additional cost besides style--assuming equal fit for alternatives. 

Then I was recommended to try the Icon Variant by the folks at Ottawa Goodtime Centre. Apparently Icon is the last helmet manufacturer to cater to my head shape. This seems odd given how well the Hornet and XD4 fit my noggin. Whatever; the Variant didn't present any obvious pressure points after wearing it in the store for a while, although the cheek pads were unusually tight and putting it on and taking it off does a number on your ears because of the tight fit. Seemed OK so I ordered one. 

Materials, fit, and finish are excellent. The shell is a fiberglass/Dyneema/carbon fibre composite with dual-density foam lining. The comfort liner is covered in HydraDry material which wicks away sweat towards the ventilation holes. Online reviews suggest it works very well, and indeed I found it comfortable. And there's lots of ventilation! More on that later.  

Colour options for the Variant are pretty interesting and oriented to the Master Chief riding demographic. A gold visor can be ordered to complete the effect. (Camo helmet? Really?) I opted for boring gloss white to improve visibility. It's actually pretty sharp looking in its simplicity and should be cooler to wear at slow speeds.

Tonight's first ride with the Variant revealed some obvious differences versus the Nolan. First is the wind noise. It's not exactly quiet, but the frequency is more of a low roar of wind passing by the helmet rather than through it, which in the case of the Nolan resulted in more high-frequency noise. I find the low-frequency noise more tolerable when not wearing ear plugs, and it allows me to hear the engine and my surroundings better. 

Second is the force imparted by the visor. I'd expected some lift and torque when looking sideways, but not this much. While my WR250R doesn't have a windshield, I was surprised to find how little buffeting the bike presented compared to my KLR with the stock windscreen. I guess the WR angles the wind right up to where the Variant visor is, causing the helmet to torque back slightly. I'll have to experiment with seating position. The lift isn't uncomfortable at 100 km/hr but may become a nuisance at higher speeds, and I found myself adjusting the helmet forward while riding. 

Third, the shield has an impressive anti-fog coating. I rode right after a big evening storm, so the roads were wet and steaming and fog was forming in the little valleys. Perfect conditions for condensation, yet the shield remained clear. I did notice that after a while, headlights and other bright objects acquired a strange halo around them. Especially bright lights created a dangerous washout haze of light that obscured vision. I'm not sure why this occured - maybe some residue on the inside of the shield was the culprit. Inspection later showed an even residue on the inside of the shield, so I washed the visor (dish soap and water only is recommended) and polished it with a soft cloth. Hopefully this was just an out-of-the-box phenomenon and not a regular occurrence. 

Fourth, ventilation performance was really impressive and far exceeded that of the Nolan. Side-checks led to air coming right up to my eyes with the shield fully closed. No dead air space in this helmet! Later I realized that only half the vents were open. More playing around is needed to figure out the right venting combo for different conditions. There also wasn't a chin shield installed. Not sure if one's still in the box, but this will be essential in cold weather riding. 

Initial impressions are positive overall and I'm looking forward to seeing how the Variant performs on a longer ride. At least it doesn't look as dorky as the Nolan: one of my spawn noticed the helmet and even said something like "cool". 

Singletrack update - more to ride in Almonte area!

Last weekend we did a long day of work on the Almonte Riverside Trail, benching a further 100m or so of new section at the far end and pulling dozens of stumps. It's still pretty rough and needs a lot of hand-work to tune it for riding, but it is rideable and interesting.

This is by far the hardest section of terrain to develop on our planned route to the Mill of Kintail. However, we're almost at the end of the tricky clay ravine section and will soon turn into the next ravine which looks totally different. You go from mature hardwood forest to cedar forest that looks like it's on the West Coast. Extending the trail through this next section should be a lot easier since we won't have many stumps to pull or buckthorn to battle.

Follow along at AlmonteOutdoors.ca. We'll be organizing a trailwork day in the fall once temperatures drop a bit. The plan is to push all the way through to the Mill of Kintail this season, so we can ride our fat bikes in the snow on an exclusive 20+ km return route of single track.

In somewhat related news, my buddy Phil and I recently spent three days riding at Kingdom Trails in East Burke, Vermont. Amazing single track and well worth the trek. The Tallboy performed beautifully and we rode 100+ km and 2400m of elevation gain in the 12 hours of technical riding we did. Good food and beer too. When I have more time, I'll post some pics and vids. There's a group of us going again on September 13-15, so drop me a line if you can meet us there.