Commando motors in Featherbed frames or other frames

Rohan · Jan 8, 2014

acotrel said:
I think that with the normal yokes on a featherbed frame with 24.5 degree rake,

Most featherbeds have 26 degrees - unless its been in an accident ?

Rohan · Jan 8, 2014

pommie john said:
Only thing is that they couldn't do it in stainless for some reason

Stainless work hardens very rapidly, when it gets worked.

It needs to be continually annealed (softened) as they go along.
If they are not set up for this, they probably wouldn't want to know.

pommie john · Jan 8, 2014

acotrel said:
I think that with the normal yokes on a featherbed frame with 24.5 degree rake, it is difficult to make the bike steer quicker and tighter than beyond being fairly neutral. I'd be interested to know how much offset is there on those fork yokes, and how the bike steers under power - whether it inspires confidence or feels vague ? What size wheels are you using ?

It's a bit tricky to measure at the moment but there appears to be about 55mm of offset on the yokes. That's as near as dammit 2 1/4" which is I believe the standard offset.

The story is a little more complex in that when I bought the rolling chassis the yokes had a taper in the top clamp as most Norton yokes do. However at that time short roadholder stanchions were not available anywhere so I had to use Commando stanchions which were too long for the featherbed. The solution was to bore the top yoke to make it a pinch bolt type. We could have shortened the forks, but I rather liked the idea of being able to slide the forks up and down to change th e teering geometry.

pommie john · Jan 8, 2014

Rohan said:
pommie john said:

Only thing is that they couldn't do it in stainless for some reason

Click to expand...

Stainless work hardens very rapidly, when it gets worked.

It needs to be continually annealed (softened) as they go along.
If they are not set up for this, they probably wouldn't want to know.

That would be it. The guy who did it is also a racer and he made them for a very reasonable fee.

acotrel · Jan 13, 2014

Rohan said:
acotrel said:

I think that with the normal yokes on a featherbed frame with 24.5 degree rake,

Click to expand...

Most featherbeds have 26 degrees - unless its been in an accident ?

I didn't measure it, I simply asked the question - my friend the triton racer is very reliable. They cannot be 26 degrees and use yokes with such little offset with 19 inch wheels, everybody would be falling off them. The replica frames made in Australia are usually 26 degrees, and use 18 inch wheels - they handle radically differently to original manx frames. If you fit 18 inch wheels to an original featherbed, it usually makes the bike tend to run wide in corners, and it becomes very heavy to ride.

Rohan · Jan 13, 2014

The factory drawings are reportedly 26 degrees - same as the road bikes.

We had this discussion here previously.
Did you not take note of it ...

acotrel · Jan 14, 2014

What does 'reportedly' mean ? I know for certain the manx is steeper in the front end than the TZ350 which has 26 degree rake. The Australian made replica featherbed frames have 26 degree rake, they are changed from the original to handle differently and accommodate the effect of fitting 18 inch wheels to get decent rubber. From my own memory of manx fork yokes, you probably couldn't use them safely with a 26 degree rake and 19 inch wheels, except if the motor was a lot heavier.
Where does your info on the original manx featherbed geometry come from ? Next time I go to a race meeting, I will take my magnetic base protractor with me, and I'll find a genuine bike and measure it. I will also check with the guy who makes the replicas. This is bullshit.

Rohan · Jan 14, 2014

acotrel said:
This is bullshit.

It is - and all of it seems to be coming from the same place...
We'd rather back Mr Sprayson and the Norton Race Shop for what makes a winning bike.

oldbeezer · Apr 17, 2018

ashman said:
I still have the Featherbed oil tank and battery box will never get rid of them, I ran the bike for 30 years with them on, but the last rebuild when I had to replace my crank cases I went for a round alloy oil tank that sits under the seat tray which holds all my electrics and because I am now running a Joe Hunt maggie no need for a battery, I run my lights off my altennator with a battery elimator (sorry about the spelling) with minamal wiring (as long as the head light, tail/brake light works), I have shed a lot of weight off this bike compared to a Commando.

I am very happy with this set up now and think it will stay this way, I don't know about putting Isolastics on a Featherbed frame as they were designed for hard mounts and its been sometime since it was brought up so that tells me it might not have worked out as I think putting Isolistics in would change the handling side of the Feathebed frame.

As you can see in the bottom pic I run a catch bottle for my engine breather and have just fitted a XS650 reed valve into the breather line, the bottle is to catch any oil that blows out but only gets very little in the four years its been there.

Ashley

Just followed the link to this in the Weak link thread. I do admire your bike, at one point in time I was thinking about a Commando in a featherbed but it never happened. I gotta ask, is that a single sided lower fender stay? I guess you came up with that before Ducati came up with the single sided swing arm. I like that too, all of the other stays with extra bends or whatever look pretty clumsy to me.
Jim