not a caferacer

lynxnsu · Apr 20, 2011

About 30 years ago I decided I wanted something to carry the dog and girlfriend with .As I was racing a Norton outfit in classic racing the idea was born to build a dominator - outfit .The next few years (this was in the eighties ) I assembeled as mucd domibits as i could .Building a bike from scratch makes you a bit of an expert in recognising the right bits because if you get the wrong ones , it gets expensive...Needeless to say I did buy enough "spares" wich were of the wrong year or even the wrong make.In the end I got enough to build a dominator model88 1954 ,
And then i lost interest ,racing is a bad virus once in your blood .It also happens to be expensive.
So the domi project was put aside , until this winter . I always try to go to the IOM with another bike and so the idea was born to take the domi.
As a sidecar-tugger I made it a 920cc without worying too much about vibrations (I was still in my twenties )
But now I do , and am not longer 25
So the idea was to put it on isolastics
The result so far you can see above

Jeandr · Apr 20, 2011

Very neat, I hope you will post more pictures as you go along.

Jean

swooshdave · Apr 20, 2011

Three isos, how many links are you going to put in? At least one at the head...

tricatcent · Apr 20, 2011

There may be a problem with this Iso set up. The trouble is the isos are going to be squished by the chain tension. This will be especially bad when accelerating hard in first gear. I have calculated it before, but and I forget the result, but I think there are several thousand pounds of tension in the chain. It may be that you will need some links to hold that tension. Maybe it will work. I know some ridgid choppers have been built that retain the isos, and would have the same problem. Most people who have built a featherbed with isos use the swing arm mounting system from the Commando.

swooshdave · Apr 20, 2011

tricatcent said:
There may be a problem with this Iso set up. The trouble is the isos are going to be squished by the chain tension. This will be especially bad when accelerating hard in first gear. I have calculated it before, but and I forget the result, but I think there are several thousand pounds of tension in the chain. It may be that you will need some links to hold that tension. Maybe it will work. I know some ridgid choppers have been built that retain the isos, and would have the same problem. Most people who have built a featherbed with isos use the swing arm mounting system from the Commando.

You could almost build a longer swingarm (look at that space behind the gearbox) and move the pivot to the cradle.

grandpaul · Apr 20, 2011

That is a TRUE "Featherlastic"!

bwolfie · Apr 20, 2011

This looks like it's going to be very nice when it's done. Will there be any issues with oiling running verticle like that? Probably not, but stranger things have happened. I agree with mounting the swingarm to the transmission cradle. Will that transmission hold up to a 920? It looks like an older unit from a 650 at most.

lcrken · Apr 20, 2011

The original "Featherlastic", developed by Randy Ullery and Mike Harcourt, featured a featherbed frame with a Commando engine mounted in three isolastics, but with the swingarm still pivoted on the frame. Several were built, and worked very well. As I recall, one of the design features that made it work was a specially designed chain guide. They worked well with 750 and 850 engines. I don't know if anyone ever went up to a 920, but there's no reason it wouldn't work. Some of the bikes racked up a lot of mileage, and the ride reports I've seen all claimed they were a joy to ride. Bob Cox wrote a really detailed article on "Building a Featherlastic Norton". If you google "building a featherlastic norton" you'll find it, as well as a Cycle World article on them.

Hobot · Apr 20, 2011

!. I would NOT install 3-Three isolastics, especially on a big block. Norton team had to remove rubber area down to what remains in 2-Two isolastics to get vibes to go away in the 2000 rpm range. Add more rubber and suffer the vibes and buzz everyone whose fitting a 3rd or forth iso can't fiddle out. Rod link at top should work a treat and way way more easy to fab up that silly extra isolastic.

2. I've measured the fro/aft motion of isolastics in line of chain pull road loads to see its insignificant to change chain tension. There is WAY more chain tension changes by swing arm arc so just go for it and as Ken reports forget about it. If you launch to pull a wheelie, witness hobot avatar, iso's will shift ~ 1/4" max But only ~1/8" max if not hooking up torque enough to roll tire off rim like avatar crash photo reveals.

3. Will be a head turner and head scratchier where ever it goes.

lynxnsu · Apr 21, 2011

swooshdave said:
Three isos, how many links are you going to put in? At least one at the head...

I do indeed plan a link at the head I have welded 2 gussets on the toprails to sandwich the rose-joint , but i only put it in because the front iso is quite narrow and so might allow the head to move lateral .An alternative would be to set the iso's really tight but that would ruin the elimination of the vibrations

lynxnsu · Apr 21, 2011

swooshdave said:
tricatcent said:

There may be a problem with this Iso set up. The trouble is the isos are going to be squished by the chain tension. This will be especially bad when accelerating hard in first gear. I have calculated it before, but and I forget the result, but I think there are several thousand pounds of tension in the chain. It may be that you will need some links to hold that tension. Maybe it will work. I know some ridgid choppers have been built that retain the isos, and would have the same problem. Most people who have built a featherbed with isos use the swing arm mounting system from the Commando.

Click to expand...

You could almost build a longer swingarm (look at that space behind the gearbox) and move the pivot to the cradle.

The purpose of the build is t o make a domi look-a-like so as little as possible alter the looks .
Putting a swinging arm on the engine-plates or make a longer one would give it away
when in the frame the isolastics are hard to spot , that is why the front one is so narrow

Sorry to reply in different goes but I am useless wth a pc....

lynxnsu · Apr 21, 2011

lcrken said:
The original "Featherlastic", developed by Randy Ullery and Mike Harcourt, featured a featherbed frame with a Commando engine mounted in three isolastics, but with the swingarm still pivoted on the frame. Several were built, and worked very well. As I recall, one of the design features that made it work was a specially designed chain guide. They worked well with 750 and 850 engines. I don't know if anyone ever went up to a 920, but there's no reason it wouldn't work. Some of the bikes racked up a lot of mileage, and the ride reports I've seen all claimed they were a joy to ride. Bob Cox wrote a really detailed article on "Building a Featherlastic Norton". If you google "building a featherlastic norton" you'll find it, as well as a Cycle World article on them.

THANKS
I could not believe to be the first to build one so i will have a look , but not to close as I like to make my own mistakes.
The thing about the chain does do me good however as i was planning to build a chaintensioner into the original chainguard , but that would have been a dificult one as there is so little space .
I will now try without that , and as the 2 rear isolastics are wider and more sudstantial than the small front one I suspect it will move more at the front
But thank you for the articles

Hobot · Apr 21, 2011

A chain tensioner would also solve chain tugging issue if found to even be an issue.
I may have too on my Cdo special d/t 2" longer shocks. If handling like a Featherbed is still apart of the appeal but not the harshness then might consider a hidden low front rod to restrain side to side and leaning bind issues so tiny isolastic only has to absorb engine bounce and can be set lose enough to do so w/o upsetting in long held powered sweepers on wavy surface. A rear link might do even better. Do not put on all three or Peel may have trouble keeping you in sight.
May have to narrow the width of the front cushions to get isolation down where desired. Love these self imposed restrictions but that makes seeing others creations such neat surprises and double takes.

lynxnsu · May 8, 2011

The forks are being build with commando internals but with the springs shortened by 3.5cm
The rods are shortened by by 5.0 cm and alloy tophats are turned up and threaded to locate the springs .By cutting the additional 1.5 cm of the rods I have done away with the part of the rod witch screws into the big nuts on top and the patr witch loccated the nut (normaly on top of the rod to locate the spring)
I will try to post pic as well

lynxnsu · May 8, 2011

the small springs on the left are an afterthouhgt
to avoid clonking when pulled on the main stand these valve springs will avoid the alloy tophats to loose contact with the big topnuts
Once off the mainstand the weight of the bike will easyly compress these valve springs and making them act as a spacer
The lenght of these feeble springs can (and probably will ) easily be altered , because undoing the big top nuts are no longer connected to the damperrods

beng · May 8, 2011

I am thinking that taking a chassis that was designed with, and to use a rigidly mounted engine/gearbox unit and eliminating that element is going to make the chassis more flexible and the handling worse. But as a comfy ride for an old gentleman at cruising speeds it probably will not be noticed.

lynxnsu · May 9, 2011

beng said:
I am thinking that taking a chassis that was designed with, and to use a rigidly mounted engine/gearbox unit and eliminating that element is going to make the chassis more flexible and the handling worse. But as a comfy ride for an old gentleman at cruising speeds it probably will not be noticed.

Well there is a first for everything .I have never been called an elderly gentleman who cruises at moderate speeds .
I must say I like the idea
However if you happen to be in the IOM this september we could have a cup of tea and nestle ourselves in comfy armchairs and talk things over .
Or we could have a lap over the mountain ,me following you of course (or would that be off course )and see for ourselves how badly she handles

I agree however that the engine should ideally be rigidly mounted .But the cradle is not tampered with and the crosstubes wich have been cut away are replaced by modified isolastics , so that the adjuster is not adjusting the width of the frame (as on std commandos ,no not on mine ) but only the sideplay of the engine-gearbox assembly.
In a smaall book i have ,written by McCandless , he says that fitting the twin engine in a featherbed spoiled its handling .
I am the last person on earth to question Mr McCandless expertise but am still impressed with a twin engined featherbed.

all this to say that I agree that ideal it should be rigid but it will not be , because that would spoil the exersise
when

jseng1 · May 9, 2011

To avoid clonking fill the small 1/8" holes in the fork tube near the bottom. Drive something oversize into them. I don't know why these exist - they are useless and make no sense. Without them you get a hydraulic stop and the clonking is gone.

Hobot · May 9, 2011

After plugging the weird totally useless bottom damper tube holes, can even fill with epoxy as nothing gets into that area, other tap in Al pegs that cross the tube then file smooth - new hole are created 1/2-3/4" above the bottom damper tube rim. Let your intuition guide the total hole area and to stagger holes in 2 size.

If the damper rod is long enough inside damper the Roadholder top bushes will cover the stanchion holes for top out hydraulic silent stop too.

Valve springs are wonderful to correct forks back as designed to function.

lynxnsu · May 9, 2011

jseng1 said:
To avoid clonking fill the small 1/8" holes in the fork tube near the bottom. Drive something oversize into them. I don't know why these exist - they are useless and make no sense. Without them you get a hydraulic stop and the clonking is gone.

thanks for the advice
But the clonking I mean is on full extension , not compression ,because the rods are no longer attached to the top nuts

not a caferacer

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