hi im new to the forum

[JAP]

im from UK warwickshire and im building a 1920s style motorcycle with a 350cc jap engine any tips would be great.
i need a clutch and a gear box.
PS i know the welding needs cleaning up a bit

[esometisse]

the welding needs cleaning up a bit

umm....indeed!

Look at as many pictures of 1920ies bikes as you can find on the web to get the style right and make your needs known in the autojumble section! Good luck with your project!

Cheers
Andy

[wetdog]

be sure you dont kill your self , the frame does not look to safe to me

[twolitre]

be sure you dont kill your self , the frame does not look to safe to me

I agree.
I did not want to cool enthusiasm in a very worthwhile project, so I did not post my concerns about the welding.
There looks to be almost no penetration on the "welds". "Tidying" them up will not cure that. Also the welds (frame?) ought to be annealed to remove brittleness.
Jim.

[Rex]

Yeah, me too, I'm afraid. While we're on an enthusiasm-killing rant, the fork links probably need to be thicker. Even quite light-weight bikes had thick steel pressings here, and most had forgings.
Incidentally what steel tubing are you using?

[JAP]

 Your honesty is valued, i did think that the fork links were a bit thin.
As for the welding i have taken it back with a grinder and will heat the joints before re welding them.
Its so kind of you guys to help out like this, i didnt think i would get an answer.

The bolts i will be using for the fork links are 12mm thick, is that OK? i have put bronze bushes were the bolts will go through.
Today i have made a bracket for the magnito to go just under the carb.

[Rex]

I've always used EN8 or EN16 steel with threaded ends here rather than bolts, but I suppose it really depends how you've designed it. Four long pivots gives strength and ridigity as you don't want either side of the fork trying to move independantly of the other.
It's an MOT test point (the amount of shake at the pivot/bush area) so they need to be machined/reamed exactly for a nice sliding fit whatever you use.

[wetdog]

wheres the dampening on the forks , might be like a pogo stick

[JAP]

could you explain DAMPENING ? have you a photo. and how thick does the fork links have to be?

sorry about all the questions.

[R]

wheres the dampening on the forks , might be like a pogo stick

Damping on girder forks was quite a late invention - girder forks WERE pogo sticks for many decades. Not many early teles had any real damping either...

A simple hydraulic steering damper adapted to the girder fork action gives fork damping decades beyond their design...

Think that frame should be professionally welded....

[wetdog]

Damping on girder forks was quite a late invention ? how late ? how early are you talking , do you think it was a good idea
A simple hydraulic steering damper adapted ? will not work you need to take a good look at how they work

[R]

A simple hydraulic steering damper adapted ? will not work you need to take a good look at how they work

I've seen them fitted and working.
Damping the basic girder fork action, that is.
Not acting as a steering damper.

Damping on girder forks was quite a late invention ? how late ? how early are you talking , do you think it was a good idea

You don't see too many 1920s bikes with any form of (friction) damping on the girder forks. And they all (?) survived.
Hydraulic damping didn't appear until the 1940s (?).

[wetdog]

I've seen them fitted and working.......where ? my understanding of this type of unit is that it works in both directions and would only make the forks ridigid , when what you need to do is control the rebound this is the job of the friction dampner and they work well if set up correctly . if youve ever made a tank out of a cotton real , a candle , elastic band and a touth pick you will understand how this system works , the 20s bikes comment i dont understand sorry , can you show me a pic of your system in use i may try it myself i have many girder fork machines all with friction dampening of differant designs .
http://s1205.photobucket.com/albums/bb429/1wetdog/?action=view&current=myoldbikes012.jpg
here are some extra fitted to my sunbeam bently and drapper

[rogerwilko]

I wouldn't worry about welding or damping etc, because this bike will never be registered. It's obviously a showpiece for his lounge.

[wetdog]

i am inclinded to agree but still some thing to talk about and interesting to hear other peoples views , i am about to learn somthing new maybe