The Worlds Fastest NIMBUS

[octane]

Thanks to a friend of mine called Kim, I've had a couple of
great visitors here in the workshop lately.
Kim btw. is a Nimbus nut-job ( and I mean that in the most positive way possible ).
A few years ago he gave himself a 50 years-birthday present:
a 2 month tour around Japan on his Nimbus.
Shipped it to Tokyo and had an epic journey.
Here's a brilliant picture of his bike with a couple of Japanese cops
sporting, what appears to be Startreck uniforms:



First visitor was a guy and his wife, from Vermont USA, dropping by on the way to the airport
after a visit to Sweden and Denmark.
He's a brilliant engineer and a Nimbusnut.
He and his wife have started the " Intergalactic Nimbus Club / Vermont Chapter ".
They, and their dog, are the only members. She is the 'President and Grand Vizier'
and he is CEO ( Chief Engineer Officer )...not sure about the dogs position.
Top Dog, perhaps ?
Got meself' a t-shirt:



They claim that the spelling-error on the t-shirt is due to the fact
that their dog 'Radar' edited the graphics ( 'due to lactose intolerance issues' ..
he made the error.... I don't think they claimed to be 'normal'...or maybe it's just the dog
who's a bit wonky
.-)



Don't ever let your dog near the 'puter !

Mr. CEO, among other things, makes an improved clutch for the Nimbus:



The Nimbus has a ( car-like) dry-clutch, which isn't the best set-up the world has seen.
His modification addresses some of the problems, like the fact that the springs
do not place an 'even' pressure on the clutch-plate and therefore this tends to
warp given time. He fabs an aluminum-ring in which the springs sit
so as to give this 'even' pressure.

Anyway; a little time later I got this absolutely freaking unbelievable email from the
CEO:

"...I will offer, if you like, to install my last remaining aluminum ring into your flywheel.  I might also like to offer that if you were to send me your flywheel and crankshaft assemblies, I can have that all dynamically balanced for you as a unit after the installation.  In addition, I have a technique to balance the large end of the con rods so they are all identical to less than 1 gm.  IF you want we can also look at balancing the smaller ends in conjunction with the piston you will install on each.  All you need to do is to let me know.  I can make that contribution to your efforts!.."

SERIOUSLY: what can I say, except for being totally in awe that
such kindness still exists out there.
Gotta' fill up my Karma-account to put things into balance again after this, don't I ?!

...then some days later I had a visitor from Sweden.
Showed up on this:



Turn out he wanted to make new parts for the frame-assembly.
( They are running short now )
Then, why not, make a complete new frame ( the black'ish one at the rear )
...ride it to bits to test it...and then start fabricating the bits needed.
That's what he's done.
Simple ...erh ?!

We had a long talk about my two main challenges :
..One: having someone make a 4-speed,  but HI-geared set of internals for the gear-box.
Long story, but LO and behold; turns out he's the man behind the
fabricating of the new 4-speed boxes, and he'd be glad to invite me up to his place
in Sweden and we'd go talk to the guy who actually makes them,
and surely we'd work out something.
..Two: I need an 'extended' cam-shaft , so that on the extension I can
mount a pulley that will drive the blower.



No problem: he was just starting up the fabrication of new cam-shafts
( running short of them as well ) and making one with an extension for me
would be no problem.

The world is still a great place with an surprising number
of good and kind people !

[Dr Goggles]

Hey Lars, nice work,most entertaining, its not surprising those others want to get involved,

"They dont pretend to be normal"...Hahahahahaha
Jeez i laughed.......

[Tman]

Awesome update Lars!

[Freud]

He's one of us.

If he approaches from Mexico he can get insurance,

food stamps, health care, a cell fone and a GPS that

will take him to every shop that's needed to make

his parts. Now all he has to do is get to Mexico.

Too bad Dolan has passed. Jack would help him to

the very end.

FREUD

[wobblywalrus]

Thanks for posting that video Lars.  That brought back memories of racing those bikes on roads just like those shown -when the machines were new.  I thought it would be something I never would see or hear again.   

[octane]

Thanks Goggles, Tman and Freud !
You're welcome Bo. Nothing beats noisy old motorcycles !


Where were we ?

Ohh yes: the frame !



The tubing arrived and I could start assembling what will hopefully one day
be a functional bike that will roam the Salt at incredible speed.

A note here:
The parts you see here shows how I approached this silly project.
The idea was to use as much parts that I already had as possible.
 Mmmm: 'idea' may be the wrong word...'necessity' might cover it better.
I've been..erh....financially challenged lately so this really was the only way.

...rear wheel; comes from a Honda GL1000 on which I replaced the wheels.
I wanted a smaller-than-(Nimbus)-standard rim so as to lower the bike. (*)
Also it is wider and more 'solid' than the Nimbus rim.
Fortunately both the Nimbus hub ( with the shaft-drive-thingy ) and
the Honda hub have 20 spokes, so I can move the Honda rim over.
...front wheel also from the Honda ( sans brake-disks )
...tank: from an old moped
...front-forks is from a HD Sportster . Bought cheaply for the Indian build,
but never used on that
...fairing: Danish made fiberglass fairing made for the MZ bikes waaay back.
Traded it for a 'Easy Rider' poster and some change.
...blower: reserve-blower for the Indian ( second-hand from an eighties Subaru mini-car )
...carburetor: reserve carb for the Indian ( off a Harley-something )

Time to move stuff over from the original-frame mock-up
to the new frame



..holding things together with wooden thingies.


Checking for room / position for the blower


 

and trying to figure out the intake side



...and after a quick trip to the HomeDepot equivalent
I did the Intake Version:2



Mmmm: not bad. This might work.





Figuring out additional tubing:



Gonna' need something up front to stiffen up the head-stock
and that will act as a mounting for the tank as well,
and something at the rear as well.

Bought a p.o.s. tube-bender from 'BilTema' ( the local equivalent to Harbour Freight ).




Considering that I have never ever bend a single tube in my life before ,
it went pretty well....after a couple of not so brilliantly brilliant
attempts that is.



and it was time to assemble the frame.
Started with the 2 upper rails and my neatly (sort of) bend connecting-tube
( not shown on the drawing above ):




(*) Lowering the bike / engine;
the only way to lower the engine --> bike / riding position
was to use smaller wheels as I have to keep the engine / drive out-put
in line with the  drive-shaft / rear-wheel axle, to exact measurements.
( Remember: it's a rigid set-up originally )
Fortunately I had the original frame to measure from
and later I had the original factory drawings:

[octane]

 I don't have a fancy frame- 'jig' set-up thingy ,
so I had to make do with a rather primitive way of doing it
using my motorcycle-lift and pieces of wood



...and checking and re-checking all measurements as I went along.

The most important thing was to get the
center-line / head-stock relation right,
so I made a set-up like this



Instead of the head-stock I used a long tube with the same diameter as the head-stock, the idea being that IF I had used the head-stock
and mount it with , let say, 0,1 mm precision
...now I could mount the tube with the same precision
but allowing a 1 mm error at the end of the loooong tube.
( Not sure my explanation makes sense, but the error of 1 mm on the full length of the tube, would be x times less at the upper 'smaller' portion of the tube)

Also, this system allowed me to 'lift' up the 'head-stock'-tube



...grind off a little of the upper tubing...lower the head-stock tubing back again..
...check if it 'matced' ....grind off a little of the upper tubing ...etc...etc
using first an angle-grinder , then the red-'trunk'-sanding thingy on the lower right here



then a bit of hand-filing...
until it fitted as intended






Same thing for matching up the lower tubes to the 'head-stock':



..'bend' it outwards....grind a bit...match up...grind some more ...etc...etc..

That one was a bit of a challenge, as the angles of the grinding
were a bit complicated



...but all in all it worked, though is was somewhat time-consuming
( but who cares ... not me )





Then it was a matter of cutting off excess tubing and tack-(TIG-) welding.
The whole thing will come apart later... the real head-stock will be mounted..
...and a friend will do the actual 'full' welding.
For that we'll go to another friends work-shop, and do it on a proper
big-a$$ welding-table.

 Yeah: I know the way I mounted the lower tubes to the head-stock
is un-orthodox.



 It's a long explanation, but basically I did it that way
so that during the set-up and the assembly I could change/alter the angle of the
head-stock, as I wasn't quite sure what the hell I was doing ( am I ever ? ).


Then on to the rear upper-lower tube connectors




At the end I was pretty pleased ... again: taking into consideration that this was the
first time everever that I've done anything like this.


Off the bench it went, and it was time for a new mock-up.
Whoohaa: it almost looks like a bike, doesn't it :




.

[octane]

Needed some kind of exhaust.
This being a blown engine the rule is:
make it as short, nonrestrictive and big-diameter as possible.

Played around with pieces of cardboard





then on to a few drawings with measurements
and back to my computerfancypants colleague,
who in a few minutes produced this



..then onwards to my new-found tube-bender friend,
to who I handed over the 3-D file
and for a very moderate sum he made them up in
thick-wall'ed  Ø = 40 mm aluminum tubes



...then out to my friends construction place where they,
after a short instruction, let me use their milling machine
( that was a first too...quite exiting I must say )
to make four 40mm precision holes in a 10 mm piece of aluminum
to act as a mounting-plate ( tubes/plate will be welded' on the 'back'-side )



Why aluminum ?
..mild steel would rust and rut away in no time
..stainless steel I can't weld, as a rather complicated back-gas (argon)
thingy is needed, and besides it's tough to work with ( like doing that mounting-plate )

I searched and searched the inter-web for information
on the viability of this.
A bunch of people on different forums I read, said it wouldn't work /
the lower melting point etc....but then I read some people who had actually
done it with no problems.
I may be daft, but I can't see the problem...hey; an air-cooled bike
like my BSA have cylinder-heads ( with exhaust 'exits' ) made in aluminum




and btw. it turns out a few American cars came with aluminum exhaust/headers.

Donno....we'll see.

But it looks pretty freaking neat...ai ??? !




( Yep; they will be shortened at final assembly )
.
.

Cost so far for da' Bonneville Nimbus: $US 629.32
.

[tauruck]

Those must be the best looking set of pipes I've ever seen on a bike. Excellent work. Why won't they work?. It's not like the bike will be standing in one place, you'll be getting cooling from airflow and you used a nice thick walled tube. I like.

[saltwheels262]

the motorcycle is really coming along and looking nice, Lars.

very detailed build diary.

Franey

[Crackerman]

The aluminum pipes will be fine as long as you dont use heat wrap on them. Once you do they will over heat and blow out.

[Glen]

Lars, awesome design, and great craftsmanship. love it. Wish we were closer so I could see for real. Your way of doing things is like old school thinking. My dad always told me to make a template first as it's easy to modify and fit. then make the real part. if something happens you already have a template to make another. Sure like the build pictures as you go.  

[Nortonist 592]

HI Lars.  Looking well.  Stan Back sent me this video.  A vintage bike hill climb.  About 3:20 in there is a Nimbus.  Good sounding one too.  Looking forward to seeing you on the salt next year.

http://youtu.be/g-I38mZmZNk?t=2m56s

[Geo]

Two guys went around to world on their nimbus's. Here is the link: http://kingcroesus.blogspot.com/

They talk about the problems with clutches, heat, etc. and the solutions with info on all the nimbus experts including the 4 speed trans update.

Have fun!  I am reading this!

Geo

[lsrjunkie]

Awesome! The exhaust looks beautiful! Great work octane. I love the frame as well. I'm a bit of a wierd duck when it comes to bikes and cars. That being said, I love what your doing. And the fact that it's a Nimbus makes it that much cooler. I'm hoping to see this machine fly down the salt in the near future.