After mentioning what a great education is available at Used Honda University and other DIY training centers, Richard Pollock of Mule Motorcycles describes a recent semester where he studied hard and earned some extra credit.
I received a “Masters of Exotic Metals” at the college of hard knocks.
I recently built a very exotic Triumph based on a new Bonneville motor. The primary goal was weight reduction. Starting out with a very heavy motor, it doesn’t leave much to work with in the chassis department. I had basically 100lbs (minus motor), as a goal, while still maintaining somewhat of a traditional looking streettracker styled, street legal bike.
So how do you get a rolling chassis, with tank, seat, lights, exhaust, brakes, battery and electrics to come in at just 100lbs? Not easily and certainly not cheaply. The first thought most people have is carbon everything right? That won’t satisfy the “Traditional” looking part, but yes, perhaps there could be some carbon worked in.
The most straightforward way to lighten parts that need the strength or structural integrity close to that of steel is to make them from Titanium. Wow, Titanium. Just that one word instills a sense of awe. The most common alloy bantered about while benchracing is Ti. Have you ever worked with it? I hadn’t, even though I’m a “Spaceship” mechanic by trade, our Spaceships use very little if any at all.
So here we go, diving into the unknown and the beginning of my “Practical” education in Titanium. I’ll share some critical lessons that have all been learned the hard way, hopefully saving you from the pain and suffering of enrollment into Ti-Ed. Please note that I’m not a technical expert and the lessons continue!
Lesson One: First, Ti is light. How light? Unfortunately not quite as light as you thought. On the weight scale, steel is heaviest, with Ti at about 65% of that, aluminum at about 50%, Magnesium is at 45% and carbon is just crazy light. So when you figure in the expense and hassles of Ti, remember that it’s the absolute final thing you do to make your machine lighter. For example, I built myself an XR650R Honda flattracker. The bikes are very heavy stock, on the order of 270lbs. I needed to be in 220lb range with 50% more power to also added in! A bet for a breakfast burrito said I wouldn’t make 240lb, so at that point, no expense would be spared. One of the lessons learned was that by modifying a 76 YZ400 aluminum tank, I saved 7lbs over the original monster offroad tank. Cost? About $60.00 or so. Next, I bought every single Ti bolt I could find for the entire bike, not including the axles and swingarm pivot. I trimmed 1.5lbs at a cost of $630.00. Ok, we need to start thinking about cost per pound when embarking on a weight cutting mission. Comprendez? Do everything else first before you purchase your ticket to Titanium-city.
Lesson Two: Titanium is very expensive! Axles, nuts and other assorted parts needed to be machined up by my local neighborhood aerospace machine shop, but they suggested I supply the material. No problem right? Holy crap! I ordered a piece of 1” x 36” bar that set me back close to $400.00 with shipping. The good news is that shipping Ti stock is cheap because it’s so light! I think I ordered maybe one more piece and then turned to “Raw Material” on eBAY. Ok, now we’re talkin’. I started buying remnants in the sizes I could use for $6.00-50.00. At least it became affordable.
The downside is that machining, drilling, cutting or welding all present new challenges, which equate to higher costs. At my local machine shop, the machining costs were about 20% more, plus I had to pay for a lot of tooling. Tap a hole, as in one hole and then throw away the tap. Drill maybe 2 holes and the drill bit is toast. And Ti has an appetite for not just any old tooling, but the really expensive, exquisite stuff.
Lesson Three: If you’re gonna drill or tap this stuff yourself, don’t. Unless you have lots of high quality, sharp drill bits. Personally, I have never successfully tapped a hole in Titanium. But I have broken off several taps halfway into tapped holes, so I’m halfway there most of the time! Drilling Ti requires more pressure than drilling a hole in steel and a much slower speed. If you almost break through and then it gets really hard to drill and you don’t see any chips being created, you just smoked a drill bit. Important point here. If you continue to try and drill with the same bit and more pressure, the material around the hole hardens up like a diamond. The titanium actually starts welding itself to the bit and common sense will tell you that a drill bit with a glob of Ti welded to the end of it doesn’t drill very well. You’ll begin to wish you’d just had the machine shop go ahead and do it. A couple more bits and you’re through!! You need lots of Ti specific drill lube (see lesson 3!). What I do at home is drill halfway through and then let the material and the drill bit cool way down. Then proceed.
Lesson Four: Trial by fire! This is a true story. However, if they find out about it where I work, I’ll deny it profusely and tell them I was just taking some literary license. Anyway, I was at work and during lunch I decide to “Lighten” up a piece of Ti with some .375” holes. I was doing well and was still on the first drill bit. But things were heating up and I was increasing the pressure. I decided to get some lube. It was a petroleum based lube called LPS. The next thing I know, I’m spraying LPS all over the material and some even got on the drill chuck. This was no ordinary drill press. It’s a very big, powerful, expensive one. It matches the cost of Titanium perfectly. What happened next was kind of a rapid fire blur. Lots of pressure, the tip of the drill bit turned red like a nighttime photo of a brake rotor on one of the big Porsches at the 24 hours of Daytona, and then a big whoosh as the lube turned in a giant fireball doing about 1200 RPM’s! Holy F!!!!! The air-hose was attached to another machine and wouldn’t reach anyway, the fire extinquisher was 100’ away, the water bucket for cooling parts was empty and lastly, my heart was about to leap out of my chest, closely following my BOE (bugged out eyeballs!) I blew it out rather quickly and cleaned up even quicker. Ok, I need to find out what kind of lube to use on this stuff.
Lesson Five: Over-expansion. While doing some exhaust work today, I was expanding the end of a piece of tubing to make a slip fit joint. I was doing a practice run on a 3” long piece of scrap material to get the hydraulic/electric expander set correctly. I had the head screwed down way too far initially and when I hit the pedal, the tube went to the point of splitting in about one second. Although, it didn’t just break or split. It split while making a big WHAM sound and shooting a fireball right at me! WTF?
Lesson Six: White sparks! My friend Don, way back in my Air Force days of the early 70’s showed me something really cool one day. If you hold a piece of Ti against a grinder or belt sander, the sparks that fly off are white! Cool! Fast forward about 38 years. I’m standing in front of a 10” wide belt sander contouring a piece of Ti with white sparks flying everywhere. I actually learned two lessons at once this day. First, if you grind on the end of a piece of tubing which fills with these pretty little white sparks, the tube turns into a bright flashlight. Very bright!! Second all the dust from the sparks that lands on your arms or t-shirt create an odd affect. I took an air blower and blew away the dust. My new Porsche T-shirt was destroyed with tiny holes. Conclusion. Those pretty little white sparks emitted from Ti are not just its “Signature”, they’re white because they are white hot!
Finally, after asking around and reading up I’ve discovered that Ti is for the experts. It takes special tools, handling, lubricants and a certain level of skill. I’m getting smarter and better at working with it. If you’d like to read a very good book that has an interesting take on the development of Titanium, I recommend The Skunkworks by Ben Rich. They tell all about the design and development/construction of the SR71 Blackbird. It was built with a Titanium skin as well as most of the rest of the plane to withstand 2000 degree surface temperatures in flight!
As Richard’s experience clearly shows, learning can be a helluva lot of fun but it’s not for the faint of heart. The thing is, after going through this process, he now has a large chunk of practical knowledge he didn’t have before, the same kind of knowledge you can get at your own DIY technical institute.
Go ahead, sign up for a class and dive in. Start today!
And welcome Richard as a new contriutor to The Kneeslider! Richard, as most of you know, is “Mule,” the builder responsible for the superb street trackers from Mule Motorcycles.