450 frame bracing

[Jordan]

I like Eldert's solution to making the frame more rigid. It looks neat and subtle. It's just a personal preference, but I think the extra flats on factory 450s look untidy. Having owned and ridden many widecase singles, I haven't felt any difference in handling but I guess there must have been a reason for the extra gussetting. As Bob says, it was probably to prevent cracking. 450s do vibrate a bit more.

Jordan

[Eldert]

i build that caferacer about 12 years ago . if i would do it over again i would add more bracing
the area where the rearswingarm pinch bolt setup is flexes a awfull lot .
no matter how tight you pinch the bolts after a spirited ride you allways have axial play on the swingarm
thats why on john jupiters scrambler someone added a piece off threaded rod to pull things together
and eliminate axial play

i added this little piece off tubing



a close up of the caferacer tubing



on my home made chrome-moly raceframe we did this to reinforce things



Eldert

[Jon Pegler]

I am not sure how much stiffening is caused by the extra bracing welded onto nthe 450 frame as standard. Some, but possibly not a lot.
The swinging arm is another matter.
This was always a weak point on the Ducati singles.
Many people racing narrowcase singles fitted an extended swinging arm pin, using extra brackets welded onto the diagonal frame tubes going up to the rear shock mounts. This might have stiffened up the swinging arm support, but did not alter the fact that the swinging arm itself was probably flexing.
Some of the scrambler swinging arms had extra bracing welded underneath, a bit similar to the 450 frame bracing, in an attempt to strengthen up the back end.
The problem is quite likely caused by the bending of the swinging arm itself, whilst cornering.
Possibly the best handling narrowcase frame was the Spanish 24 Horas. If you haven't tried one, you don't know what you're missing.
This used a heavily gusseted swinging arm made out of 32mm tubing. It was only 16.5 inches long (approx) from pivot pin to wheel centre.
Compare that to a standard 450 swinging arm. 30mm tubing and 18.5 inches centre to centre ( Again, an approximate figure, depending on how far the rear wheel is pulled back in the rear fork)
I consider that the 450 handles well, even with my modified pivot arrangement, but the 24H is certainly more rigid.

[Teckhardt]

if i would do it over again i would add more bracing the area where the rearswingarm pinch bolt setup is flexes a awfull lot . no matter how tight you pinch the bolts after a spirited ride you allways have axial play on the swingarm
thats why on john jupiters scrambler someone added a piece off threaded rod to pull things together and eliminate axial play

So do you think the factory 450 plating is better at reducing flex than the tubing you did?

I might add the threaded rod to mine as an extra measure. The small pc of tubing in the Y behind the axle tube looks like a good idea as well.

[Eldert]

So do you think the factory 450 plating is better at reducing flex than the tubing you did?

.

i dont know if the factory plating is better or not but ift prevents the downtube from cracking 1 or 2 inches from the top

the very first widecase frames did not have the curved loop behind the rear motormounts . the frames started cracking
where the plates where welded to the tubing

and John is correct that the rear swingarm is very weak and flexes a lot .
for our raceframes we build a swingarm out of 35 X 2 tubing with a lot of bracing



the only thing is its weights 2kilos more then the original item



Eldert

[Teckhardt]

OK folks, please chime in with opinions. My cafe frame is still in the mock up stage so now is the time to do all the bracing to make a nice rigid frame that will not crack.

Plan for frame is:

Add the tube from the axle tube to the y of the down tubes
Add two tubes from axle tube up to the backbone
If the tank mounting allows, add a tube on each side from the down tube to the backbone
Use the cross bolt thru the axle trick

I already have a 450 style swing arm with the extra bracing welded to the bottom. Plan for it:

Add a plate over the open square from the axle tube to the half moon brace

Is this overkill or not enough? A little extra weight will not kill me but I don't need to add it if there is no benefit.

[Eldert]

there is one other mod i did to my caferacers swingarm .
my brothers swingarm cracked right where i drew a line with a marker .
so i welded a piece of angle iron in there that tapered down

another guy i know had the same thing happen to his swingarm and only on the l.h. side to
maybe it has something to do with the brakeplate



Eldert

[Jordan]

if i would do it over again i would add more bracing
the area where the rearswingarm pinch bolt setup is flexes a awfull lot .
no matter how tight you pinch the bolts after a spirited ride you allways have axial play on the swingarm

I don't have the problem, I guess I'm not so spirited!
To understand, is it that the clamps aren't able to grip the spindle tightly enough, so it's able to slip sideways?

Jordan

[LaceyDucati]

With reference to using a 450 in a 350 frame I thought the following information may be of interest.

We have successfully raced a bored and stroked 450 , taken out to 490 which is mounted in a 350 chassis. We did add bracing to the frame similar to the 450 using flat plate along the tubes leading up from the rear engine mount up as far as and on to the backbone. However we did not continue along the backbone as on the standard 450 frame. We originally used a 350 swinging arm which was braced around the forked end to achieve the same objective as Elderts mod and also boxed in the swinging arm in the middle to stiffen it. We have subsequently replaced the swinging arm with a new manufactured one in 35mm OD tube 2mm wall thickness, again much as Eldert.

We have raced this machine for quite some years now and experienced no breakages. Therefore I would conclude that a similarly modified frame for road use with a 450 would be more than adequate and quite possibly just using a 350 frame for the road would not lead to too many problems.

On a cautionary note,with all this talk of bracing frames and associated welding, care should be taken to check the frame for straightness and straighten if necessary. You would be amazed how much distortion can occur with the smallest of welds.

Attached picture of Nigel Palmer racing the 490 at Cadwell Park - 350 swinging arm in the picture. Not many Ducati Singles get this much of a work out and I would doubt if any significant handling issues show up on the road under reasonable use with a standard frame.
Nigel

[machten]

What a cracker of a picture!!!

Kev