Friday, August 19, 2011

What I Did on my Summer Vacation

Well, ...not really.

I did take a few days off recently to attend the NVMDRA vintage nationals in Harrisburg, Illinois though. We have to enter that story at a point about a week earlier though. A week ago Sunday afternoon, I decided it was high time that I started the Knuckledragger to check out a few things.

Number one was how it would react to dropping the clutch at RPM on dry pavement. Due to various minor setbacks since I did the initial start up on the Knuckledragger late last summer, the only running under power has been in the "burn out pit" here at the shop. Now, the Knuckledragger is set up to replicate a mid '50s drag bike as much as possible. As such, it has a vintage transmission which had been converted to a two speed (third and fourth gears only). Along with the lack of gear reduction in the transmission, it was also outfitted with a 28 tooth VL trans sprocket necessary to fit the early '30s VL frame. Add a new M&H 5" drag slick with traction capabilities exceeding '50s era tire technology by multiples of 10 and you can begin to see my concern.

The second item I wanted to get a better feel for was how good the brakes work. Stock springer front drum brakes are notoriously bad. Often, they will do little more than hold your bike from rolling backwards when stopped on a hill. I had done my best to make this one work to the best of its capability, but did it? The rear brake is of course also a stock '40s era drum. These rear brakes maintain a much better reputation than the fronts, but they are after all still just a rear drum brake. It would be nice to know in advance how well the brakes would (or would not) stop me.

The third item I wanted to check out was the shifting. The original (to this trans) set up was just not something I could make myself like. So, even though the bike only needed to be shifted once, I thought it important to know it would happen.

But, of course things did not go exactly according to plans. Somewhere along the way of making all these plans I neglected to put a fresh charge on the starter batteries. Strike one. Although the Knuckledragger did start, before I got it off the rollers, I managed to let the motor die. That is when the weak state of the batteries manifested itself. After a quick charge we managed to get the bike running again; only to do a repeat performance of stalling it. A few more repetitions of a three stooges type starting drill and I finally got the bike to the end of the parking lot and turned around. But now the engine was audibly running "sour." Now what? A valiant attempt to bring the RPMs up and drop the clutch resulted in stalling the engine ....again!

Well no sense in beating a dead horse, so to speak, so it was back up on the bench to sort things out ....much to the disappointment of a couple of the grandchildren who had been lured to the shop with promises of a daredevil riding exhibition. The excitement obviously over for the day, they went home with their parents. After only a few minutes of fruitless troubleshooting, by chance as much as anything, I felt one of the carb needles. Loose as could be. The idle mixture and the power mixture needles on both carbs were similarly loose and badly out of adjustment, having turned themselves out from engine vibration. Now, if only I remembered what the final adjustment I came up with on them last summer was ....

Which brings us up to the vintage race this past Saturday. Once we were set up in the pits, I would still need to start the Knuckledragger and adjust the low speed mixture. I had a pretty good idea of where I had adjusted the high speed, and so was less concerned with that. Most of the alcohol for the high speed circuit is supplied by fixed jets inside the float bowl, so I was using the "power" needles more like trimmers, even though with the M35 bodies it is capable of supplying a goodly amount of fuel.

Once the carbs were back in adjustment, I was ready for a pass down the track, still with the same three concerns that I had not addressed the previous weekend. Would the bike launch, would it shift, and if it did those two things, would it stop? They say with age comes wisdom ....yeah they say that, ...but "it ain't necessarily true."

The whole issue of shifting, while it would have been nice to test ahead of time, was not something that I was too worried about. Stopping on the other hand, is a fairly important part of drag racing, though to be honest it was not something that worried me too much. I have been off the end of the pavement enough times on a dragbike with good brakes that I was confident that the speeds involved would not make it an issue.

The "launch" however, was a whole 'nother matter. My biggest fear was standing the bike straight up. I had never been on a bike with a drag slick and no wheelie bars. Like I said, the tire on this bike provides way, way, way more traction than anything available back when drag bikes were built the way this one is. The chances of recovering from such a launch without major damage to the bike, not to mention myself, are pretty slim. Nearly as scary though was the flip side of that equation (no pun intended) where I bog the motor or even kill it. That would indicate a lack of power and reflect poorly on my engine building ability. Talk about embarrassing! Now that's something to worry about!

I wound up making two passes down the track on Saturday. I must say, I have mixed emotions about the results. First I'll describe how it felt from the pilots seat. On the first pass, I decided to throw caution to the wind and rev the motor pretty good before dropping the clutch. It felt like I was spinning the rear tire hard with just a hint of fish tailing. Somewhere between 100 and 200 feet it seemed that the tire finally found traction and the bike pulled like a freight train. When I shifted to high gear I had to let off the throttle (due to an unsolved issue with my shift mechanism) and when I got back on it the clutch broke loose badly, only starting to grab again just before the finish line. I fully expected to receive reports of at least a haze of tire smoke from the first part of the pass.

After wearing gloves to remove the now blue steel clutch plates and laying them out to cool, John Endrizzi (my volunteer pit crew for the day) and I found a fairly flat piece of concrete to "resurface" the fiber plates on. A little adjustment on the shifter and we were ready for one more pass, just in case our back yard clutch repair was successful.

This time my second to worst fear was realized. I stalled the engine at the starting line; no fault of the engine, I had forgotten to open the petcocks and ran the float bowls dry. Quickly back to the rollers and restart the Knuckledragger.

The second pass was much like the first, with the sensation of a lot of tire spin, though not quite as much as on the first pass. Then, again the feeling of the engine pulling like a freight train.
The shift into high gear worked essentially as designed this time, or at least a slow motion version of it. This time it took most of the shut down area to get the bike stopped, owing to the mediocre brakes.

So what's to have mixed emotions about, you ask? Well, there is this. My wife, after helping to start the bike each time, grabbed a video camera (one she had never used before, no less) and managed to record the passes. The video shows no tire smoke, in fact it is inconclusive as to whether the rear tire is spinning at all. Is it possible that what I perceived as tire spin was only clutch slippage? Don't know.

If you watch the video closely, on the second pass you can see what looks like a significant wobble in the rear wheel. It's not. After checking the bike over closely since seeing the video, I have come to the conclusion that the rear section of the frame was twisting from the combination of traction and horsepower. I hate to give up the look of the 5 inch slick, but I believe the best solution is to put a tire on the bike that more nearly mimics the traction capabilities of the era. After all, the frame is at least 75 years old.

Overall, the weekend could really only be counted a success for my wife and myself. We finally got the Knuckledragger down the track, and left with only minor issues to sort out. We had a great time and did a little sight seeing on the way home. The down side is that turn out for the race was what one participant called "a disaster." Taking place at the end of Sturgis week may have been a big factor, as well as glitches with the advertising. But, just as the Knuckledragger came away in need of some "fine tuning" to work better next time, so the NVMDRA came away with some fine tuning to be worked out. Plans are already in process towards both those goals.


Mark said...

Hi Lee, Great to see you got to run the bike, I was on John's site and saw your run there also, I think your right about changing to an older smaller style of tire you need some tire spin with a frame like that. I'm building a VLEL my self and I know what you mean about the frame, I was in the planing stages of building a bike on the lines of the Evil Mother, but between my son and you we have change our plans and are going to build a vintage drag Knuckle. How big is your motor? and are you going to run fuel in the future? also will they let me run S&S cases?
Mark. Early Iron Motorcycles.

St. Lee said...

Hi Mark, yeah, I think I need to sacrifice the cool look of the slick for the cool tire smoking runs of a different tire.

Another drag knuckle? That is fantastic!

I wanted as many cubes as practical with keeping the exterior of the motor looking period, so I had T&O build me a set of early taper 5 1/4" stroke wheels. The cylinders are repop Panhead, which bring it in at about 99 inches. I used the V-Twin Knuckle cases to keep the early style shafts. They are made by STD and have a pretty stock look though overall much stronger. I could not justify the cost of OEM cases which were liable to break anyway. (I wouldn't have built it that large with stock cases either)

I can't speak for Wayne, but I don't think there would be any issues with using S&S cases - the whole point of the vintage drags is to have fun and have a place for the old stuff to run. Wayne is talking about billet Triumph cases for a dual engine bike, so S&S should be fine.

I am running alcohol now, so adding some nitro would be fairly easy, however I don't think the Pan barrels would hold up to it. If I did run some nitro, it would only be a small percentage to get the sound; I really don't want to have to spend money on blown up parts!

Good luck on your project. It will be great to have a pair of Knucks going down the strip side by side!

steeplepipes said...

Thanks for That

Anonymous said...

Looking at that dual runner manifold I could'nt help but wonder if your "tuned leight" thoughts could have also be in how a linkert butter fly opens. It would at the start have the greatest amount of flow at the longest side of the runner?Will be curious to hear more.

Anonymous said...

Well looked again and i saw that it was upside down in the photo, so it opens to the shortest side of the runner. Is that a good or bad thing in your opinion as flower of heads and builder of fun things that get n go?

St. Lee said...

Tom, I apologize for taking so long to answer your question. I wasn't ignoring you, its just that I never seemed to have a Linkert handy when I had time to consider what you said, and I couldn't recall which way the throttle plate opened.

Now, looking at one, it seems that if the wall had been added in the other direction (90 degrees from where it is in the Seeley) it would give a better flow path for part throttle operation. I wonder if they ever considered and/or tested that.

On the other hand, it is my opinion that the "tuned length" advantage would only be effective at or near wide open throttle.

Couple of questions that may never be answered unless someone has more free time for R&D than I do.