Centre of flywheels and lateral centre of weight for a twin engine.

[Monkeypants]

I'm going to try measuring the spring rate in a hydraulic press to see if there is an large increase in pressure/inch just before the coils become bound. I have a hunch that this is the case and it would be nice to know if this is correct.

On the question of progressive geometry for the RFM, what I'm hoping to create is a shock /swingarm geometry that would have the shock travel start at a motion ratio of about .25 inch shock travel for every inch of axle travel and finish fully compressed at somewhere around .40 inch shock travel for every inch of axle movement. So the shock will be gaining leverage against the axle as compression occurs.
If the lineup of the shock starts with the bottom end of the shock being above the general line of travel and moves into the line of travel (down) as compression occurs then there should be this sort of relationship happening. To get the geometry right will require some experimenting and may even require building a second RFM after doing some riding on the first version. Before building the first version I'll build a trial unit that can be altered easily.
Before doing any of that I'll need to complete the motor mounting, since the shock attaches at the location of the rear motor mount.

 

[Pushrod Twin]

If you do run into trouble with the clearance between the front wheel and the mag cowl you could always go for series 'D' components.

Yes, thanks for that TT. I decided I had to ditch the stand brackets to make room. I have a NZ made B/C type cowl casting which will be altered to tuck in close & look reasonably standard at a glance.

 

[Pushrod Twin]

Just a thought; when I built my spine, I inserted a 2" BSP drum bung at the rear end for access to remove big end detritus.;-)

 

[Monkeypants]

good idea.... would you happen to have a photo?

 

[Pushrod Twin]

good idea.... would you happen to have a photo?

No sorry, have just read through my photos, will try to describe it, then post 1 of what I have done so far.
Started with a bar bigger than the size of the spine tube cut on an angle. Mounted in chuck, bored, & screw cut thread & seal recess. Used parting tool to cut down to dia. 2mm bigger than thread leaving 1.5 - 2mm thick end. This is the exposed end you see when welded into spine. Continue using parting blade to cut longer groove, about 20mm, then part completely off. When placed against back of spine tube, thread is inside, scribe outline of tube, then cut to shape & weld in place. If you use 2" BSP you can fit an huckery old drum lid, or, when you run short of jobs, you can machine up an alloy plug with rocker cover size hex & HRD or Vincent scroll.

 

[Monkeypants]

Sounds like a neat method, but might be a little tricky and costly for me to find a 5" dia bar in 316SS. DavidD has sent me some
photos of a removeable end he made up for the spine, that might be the route to go with SS.

I've also found a company that has weld-in 316 SS 2" bungsets for $15, will have a look at those today.

 

[Howard]

Sounds like a neat method, but might be a little tricky and costly for me to find a 5" dia bar in 316SS. DavidD has sent me some
photos of a removeable end he made up for the spine, that might be the route to go with SS.

I've also found a company that has weld-in 316 SS 2" bungsets for $15, will have a look at those today.

How about welding a 2" BSP locknut inside the tank, and screwing a Vincent twin gearbox inspection cover into it?

http://www.aalco.co.uk/technical/datasheets/Aalco_Datasheet_St_St_BSP_Fittings.pdf

There's all sorts of standard SS fittings in the UK so you should have supplies over there.

H

 

[Monkeypants]

Howard, there isn't much BSP stuff over here (Canada). Most common is NPT(11.5TPI for 2"), however I do have a lathe that will cut 11TPI. Finding large dia crops in SS is not quite so easy as in mild steel, this is one drawback to using stainless.

I'll see what these SS bungsets look like, one of those might be the easy answer. If not, a Vincent inspection cap would look nice on there.

 

[Howard]

Howard, there isn't much BSP stuff over here (Canada). Most common is NPT(11.5TPI for 2"), however I do have a lathe that will cut 11TPI. Finding large dia crops in SS is not quite so easy as in mild steel, this is one drawback to using stainless.

I'll see what these SS bungsets look like, one of those might be the easy answer. If not, a Vincent inspection cap would look nice on there.

I'm not a welder, but couldn't you gas weld a MS insert inside the tank with dissimillar rods (I think that's the term)?

Failing that, if you can wait, I can probably post one to you - may take time with Xmas post.

H

 

[bmetcalf]

Do any of these look OK? http://www.bungking.com/osc/product...d=121&osCsid=5767aea7afedc86e621f134c8a1bb13d