project

A couple of winters back I decided to build a bike with a new high performance Vincent engine and sort of an Egli type frame.

The frame would be out of stainless steel, the front end is off an 03 Gixxer (a particularly light front end) and rear suspension is of my own design but borrows from the D series Vincent rather than Egli.

The starting point was to machine up the headstock and top spine.




Glen

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I let things sit for a year while I contemplated how to proceed from here. I needed a Vincent engine to build from since I had no frame jig. My 47 Rapide was in great mechanical shape but had lots of nicks in the paint from the last 30 years of touring in Soctland, England, Australia and Canada. I decided to kill two birds and pull it apart , but I put it off until the end of the riding season in 2010.

http://s1233.photobucket.com/albums/ff3 ... ent001.jpg

First of all let me start out with being gealous of your Vincent.

I like the project idea. BUt would offer this opinion. Ditch those wheels and go with modified Harley spoked hubs. I did a set for a custom build I was going to do, but changed direction. Now I am going to use them on A norley. Here is what I ended up with. 17" deep drop center rims on ss 40 spokes. I was using a 1993 GXXR 750 frontend. Here are some pictures.






Great work so far, I will be following this one.

I contemplated using wire spoked wheels at the start, but have grown to like the Gixxer wheels . They are very light in weight and strong. The purple will go , but it doesn't matter for now. Final wheel colour will be black center with two red pinstripes and polished outsides (the flats) ,just like an original vincent.

Here is the front end

I'm a bit slow at sorting these photos and posting them to photoshop. Seems a slow way to go about it, but I guess that is the correct process here?

Here is the spine and head tube ready for heliarc with purge in place. Steel discs are made a press fit in bearing recesses in order to minimize distortion from welding.



and here is the welded spine and headtube. I gave this a triple bead and weave as it is the weld which will see the most stress (front brake) as with all motorcycles.

Nice bead.

thanks
here it is after a bit of polishing;




and here is the spine attached to front end. I replaced the headstock bearings with a new tapered roller conversion set.

next up was to mill some alloy head backets to suit my plans. The standard Vincent head brackets are cast steel and have an offset built into them to allow for the offset in the cylinders. This goes back to the conrods sitting on a common crankpin beside one another.

Figuring out just how to make these brackets was a bit challenging. Copying the stock brackets wouldn't work because the drive chain wouldn't have clearance on the large rear tire I planned on using. So there was much calculating and measuring.

My first thought was to shift the engine to the right (from standard) in order to gain the clearance. After examining some other possibilities, the engine shift was the way to go. This put the longtitudinal centre of weight of the engine a little closer to the centre of the wheels than it is on a standard Vincent or on an Egli-Vincent.

I determined the longditudinal center or wieght by placing the engine on a steel roller and finding the balance point.



here is the finished product on the engine. These are 3 pounds lighter than stock Vincent cast items.

next was to get the spine and front end lined up on the engine in order to weld the mounting tangs to the spine. I used wooden spacers for this. The important thing here is that the centre line of the spine must parallel the engine crankcase joint so that the engine is in line with the wheels and frame when finished. The engine also should be vertically aligned with the wheel and front end.








top engine mounts tacked in place, Finally!

fitting engine mount tangs. The front mount is fixed, the rear mount has a slide to allow for expansion of the motor as it warms.




Front tang thickened



rear tang slotted

starting the 1" tubing at the rear of the frame. I used the mill to cope these joints. A good fit is essential for welding this thin wall material.




had to turn up a couple of SS bobbins. These get welded into the tubing to form the lower motor mounts.



rear downtubes coped for bobbins



bobbins fit and ready for welding




welded in

I put an Oring sealed bung in the end of the top spine. The spine is also the oil tank so it will be good to have the bund for cleanout purposes.

I thought about using stainless steel for a motorcycle frame before, but I think there is a reason that you don't ever see them much, it likes to crack when it is subjected to flexing and vibration.....good luck.

No, it is much more resistant to cracking from vibration than conventional materials but it is also a lot more expensive.

It also moves more during the welding process so it does not suit mass production.

Next time you cut off a piece of stainless, say a bolt or screw, leave a little bit of material at the bottom of the cut and try bending it back and forth to break it. This usually takes one or two flexes with carbon steels. It takes a lot more effort with stainless, perhaps ten flexes or more.

There have been two other Stainless Eglis built. One is now twenty years old. Neither has had any vibration cracking.

Just out of curiousity, what grade of stainless are we talking here ?

Fabulous looking project. More, we want more !

Its all 308 non magnetic.

Ill try to get some more photos sorted shortly. Starting to get the hang of it!

removed the tacked together frame from the engine and did the final welds;






then it was back on the engine with front end attached to figure out the swing arm or rear frame member as it is referred to on an original Vincent. Egli used a regular type twin shock swing arm, about 3.5 inches of travel, similar to our Norton Commandos. In talking with Egli owners I learned that the Egli rear suspension is not great on a rough asphalt road, something I ride on a lot. A standard Vince has about 4 " of rear travel with no progression built into the linkage.

I played around with the Geometry until I got 5.5 inches of progressive travel. How it will work on the road is unknown at this time. I'm hopeful that it will give the kind of ride I want and the shock has adjustable dampening and preload so some fettling can be done.

I see this image got chopped so you can't really see what is going on at the back end. I have made up a mock wheel in wood and a mock swingarm from some leftover square tubing. In this way I could adjust the shock mounting points/geometry until the desired effect showed up.




materials rough cut to length for the rear frame member/swing arm. The rear frame member weighs 10 pounds, the rest of the frame 13 pounds, so just 23 pounds for frame with swing arm including oil tank. Very light!

Swing arm mostly done, but still needs the shock tower. The swing arm was quite a lot of work, most of which I don't have photos of. The big job was making the pivot tube. It sits between the crankcases at the back of the engine. It has to be machined accurately for length so the the roller bearings that fit into the ends of it are a push fit into the back of the engine. Any slack here will negatively affect handling. After much ado, I got an good fit on it.

I decided to make the shock tower curved to match the wheel diameter. I have seen them done with a piece of straight square stock mounted at an angle to plumb, but it looked awkward.



tire clears everything and chain line is good



and here it is with the shock tower built and the shock in place sans spring

beng said:

I thought about using stainless steel for a motorcycle frame before, but I think there is a reason that you don't ever see them much, it likes to crack when it is subjected to flexing and vibration.....good luck.

Click to expand...

Thats certainly the case, but using heavier gauge stainless tube, and keeping the welds as small as possible to minimise heat going into the tubes, would lessen the chances of cracking quite a lot.