Cycle News - Archive Issues - 1980's

frame. So I guess the answer to your question is that what I would do in my four-cylinder frame is attempt to handle the inadequacies, lhe shoncomings of other frames as best I could and not worry a bout retai1cost. Whataboutactual~rch? 18 easier to construct. But my tests showed that rectangular swinganns weren't as strong, torsionally, as round swing afrns. The first test that I did myself was simply to take a 20-inch length of tubing and weld it solidly to a piece of very thick angle iron which I had held in my vise. I welded a large diameter nut to the other end. I used a big truck torque wrench and put a pointer and indicator on the end of the tubing. I took the torque wrench and pulled on it to ISO, 200 pounds and saw by looking at the pointer how much the tube would twist. That way I was able to test the twist of the tube only and not anything else. You'll also notice that the rear axles on my swing arms aren't attached by flat plates. I try to get ahold of the tubes as good as I can, so the ends of my tubes are mitered and fitted more like a Maico swingann. Anyway, most of my swingarms are oval in cross section, not round. Rectangular cross section material is better as far as one side bending upwards, by itself. But in a swingann, if you get ahold of the end of it solidly, it cannot flex unless it can twist. So I use oval because it's better in a torsional application. People may read this and say that 'Oh, he's all washed up'. But I have done these things, and I can prove what I say. I went far enough to make the test. I think that's the thing dtat makes the difference. Let's say just for the sake of dilcuuion that you were asked to build a frame for a large, fourcylinder motorcycle. How would you figure out what the geometry of the frame should be? By making an educated guess. Anytime you do something like this, you have to make a guess. Let's face it, the approach that the Big Four manufacturers take are all quite different. Kawasaki has a tendency to use a steep steering head angle, about 26°. Most of the Yamahas and Hondas are more like 28°. Some bikes handle better at lower speeds, some bikes handle better at higher speeds. What I do is copy. I copy what I think is the best approach to the problem. I'm not afraid to say that on my frame there are things that Doug Schwerma did, and that there are things that the Rickman brothers have done. If I see something that I like, I'll try it out, and if it works, I'll use it on my frames. There isn't anyone thing on my frame that's like another manufacturer's, but I'm kind of a nut about having everything connected together real tight. I like a stiff, stiff swingarm. I always use Tlmken bearings on the swingarm pivot, because they just work better, especially under side load applications. It's surprising that Yamaha road racers have come with needle thrust bearings along wilh needle bearings for many, many years. But none of the manufacturers have ever put needle thrust bearings on the side of their swingarms because who cares if it works when you're going around the banking at ISO mph? They're never going to get ridden like that. And if they are, it's because some jerk's in over his head. So, they put needle bearings in the swingarm pivot because it's a selling point. Not because they work better than bronze bushings. That's pretty much the way most things go. You have to be able to sell it. My frames have always been highpriced, compared to other frames. My Triumph frames sold for $1000 six years ago. I haven't sold very many Triumph frames. But the people who have them appreciate them. The frames have a lot of features that are different from anybody else's Triumph I find that every day that I'm alive, I go to school. I always try to learn something. I try to associate with people who can teach me something. That's one of the reasons why Bruce Lind rides my road racers. He goes out on the road race course, rides five laps of practice, comes in, and tells me something that I can use to actually make an improvement on my bike and make it work better. Many of the people I've had ride my bikes have been jets or hot shoes, full of natural ability, but unable to tell me anything except that it works or it doesn't work. They couldn't work on one thing at a time. I have found that hanging around people like Bob Work and Bruce, people who have been around for a while, gives me an eduation in this field that could never be reached in any formal course of study. What is the geometry of your 5OO's frame? This bike has almost 26° of rake the way it's set up now, and it has four inches of trail, but trail varies by which position the rear shocks are in, what size tires we run and how much the forks are slid up or down. The wheelbase can vary from 52.5 to 54.5, and it's at about 5~ inches right now. I've found that on a motorcycle that's straight and light like this one, the trail isn't as imponant as the wheelbase itself. If you make the wheelbase long enough, you can make almost any bike handle slow enough that the average rider will be able to deal with it. What I like to do is get the bike to handle as good as it can with as shon a wheelbase as possible. Because the shoner the wheelbase the faster it can go around a small radius tum. If you look at the factory road racers, they are almost always shoner and lighter and quicke,r handling than the motorcycles that are sold to the public. That's because· people like· Kenny Roberts and Steve Baker, Johnny Cecotto can handle a bike that handles quick, because their reflexes are quick. They are people who have a very high level of natural ability. The average person probably couldn't ride Kenny Robens' motorcycle if you gave him a week to practice. When you say average penon, do you mean the average street rider? Or the average racer? I mean the average racer. The average racer never makes the main event in a din track race and in a road race is getting lapped after the fifth lap. Don't get me wrong. A lot of the things on the motorcycle can be appreciated by everyone. The light weight, the straightness and the trueness of the chassis. The straightness and trueness of the wheels, the power. But as far as handling goes, the average rider is better off with a little longer wheelbase, a little longer rake, and the average rider is also more comfortable with different peg positioning and handlebar positioning. Factory racers use different clip ons than the bikes that they sell to the public. Because the -factory riders feel comfonable tucked in with their hands laid so that they have less leverage on the bars but their bikes go straight. And their wheels are always adjusted straight. And they don't have to always pull on the bars. When they're riding down the traCk, they're pan of the motorcycle. They aren't forcing the motorcycle to do anything for them. They're just looking where they want to /{D, and the motorcycle is going where they look. Now, at Laguna Seca, Gene (Romero) was having to force his bike around. Gene had been turning consistent I: 12s in practice and he wanted to get down to 1:09s, I: lOs, down there with the fast guys and he couldn't do it. He was really upset with himself because he has sat on the pole there before. I looked at the bike and the first thing I noticed was that the frame was bent from his crash at Loudon. I didn't want to say anything to Gene because I knew it would upset him, but it was bent badly enough that I thought that it wasn't safe. It was bent far enough to the left that it didn't want to tum left. It just wanted to fall to the right and it was going to be heavy steering. So I took Don (Vesco, Romero's tuner in 1980) aside and I asked him to look at it and he said, yeah, it was bem. I told him that I thought that there were a couple of ways to handle it and that even if we didn't do anything else we should cock the rear wheel, even if it meant misaligning the chain slightly, so it wouldn't want to fall to the right and turn hard to the left, because Laguna has almost all left-hand tums. Anyway, Don looked at it and the next day brought the bike to the track wilh it the same way as it was the day before. He wouldn't even cock the rear wheel because he didn't want the chain to be rubbing on the swingarm. Myself, I think it would have been bener to beat the swingarm in with a hammer and cock the rear wheel and chew up the rear sprocket, if that's what it took. You have to have the sprocket quite a bit out of alignment before you'll have the chain come off. Anyway, believe it or not, between the first and second legs Steve McLaughlin happened to walk up and look at Romero's frame. Steve just couldn't stand not telling him, and that's' how Romero found out that his frame was bent. I had quite a fight with my conscience because I like Gene, and I felt that it wasn't safe but at the same time I didn't feel it was my place to interfere because I didn't have anything to do with that relationship. So I had to decide whether or not to tell Gene that his frame was bent or whether to try to deal with Don. I thought that the right thing was to talk to Don about it and that's what I did. Then McLaughlin comes up and tells Romero right before the [mal leg of the race. Believe or not, most high speed wobbles or other handling problems are not caused by bad alignment of the wheels as much as they're caused by other idiosyncracies like the axles not being on the same plane; the wheels being out of round, out of true, out of bounds; hannonic vibrations. It's such a deep subject that it would keep most people busy for a year just figuring out the mathematics. Several SAE papers go into it in depth and'a lot of experts on the subject still don't agree on what causes high-speed wobbles. What I'm getting at is that it's more important to think you've gOt the right tire than it is to have the right tire. And it's more important to think that you've got the best motorcycle than it is to have the best motorcycle. That's why you can do a lot of damage telling someone that their frame is bent. Gene's frame was bem, but he wasn't having problems that were scary to him. He just couldn't figure out why he couldn't make up that time. The answer is simple. The bike wanted to fall to the right, and it was difficult to tum left. He had to work a lot harder than most people to go as fast as he was going. Of course, if his bike was straight and he was working that hard, it would have been anolher story. •

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