MUTANT REDUX: A NEW VERSION OF IRONWOOD’S FAMOUS BMW

[weeksy]

You're all a bit weird!

[demographic]

I'm not right sure about the way that single shock absorber is fixed to that rear subframe tube central point.
They usually fix em onto stronger areas than that, like the part where the tubes meet, is it called the node? Anyway, its usually a stiffer area or its heavily braced.

Or put it this way, I'd want to see a tubby patty muncher take it down a bumpy road at speed before I hossed about on it.

[Mr. Dazzle]

I always think that when I see these Ks, but I think it's normally like that?

[Mr. Dazzle]

P.S.

Deftrap, with regards to Electric customs - I've posted this before. Whoever made this had a picture of me on their disk and said "I'm gonna make that bloke a bike!"

[Horse]

I always think that when I see these Ks, but I think it's normally like that?

I think Demo's right, the original was where the diagonal intersected the seat rail.

But searching for photos - it's all custom bikes!

Ah, here's one:

https://i.pinimg.com/736x/2b/0a/6e/2b0a ... ce=sh/x/im

[demographic]

I always think that when I see these Ks, but I think it's normally like that?

If youre replying to my comment about the shock absorber top mounting point I'm pretty sure the standard way is different than this and to my eyes this one looks dodgy.

[Horse]

Link buggered in previous post.

[Mr. Dazzle]

Yeah they've stuck it half way down the member.

Maybe should be in the double entendre thread.

[demographic]

Yeah they've stuck it half way down the member.

Maybe should be in the double entendre thread.

I'm honestly not totally sure if its a bad thing or not but to me that halfway down the tube looks like it would flex more than where the tubes join.
Plus any I've seen has had more bracing around it. It just doesn't look to be the best area to mount the shock absorber.

These Cafe Racers aren't exactly confidence inspiring with the way they've been built and after seeing so many that fail the most basic of inspection I now expect them to be a danger to ride.

Or put it this way, most of them look even less well put together than the average streetfighter and I hated a lot of them.

[Mr. Dazzle]

I don't think it is in imminent danger of collapse, but I also doubt they've thought about it beyond "that looks better!". Steel tends to be quite forgiving.

But yeah, it's kinda wrong. It'll be less stiff for one. You'd also need to re-rate the spring to account for the fact it's on a different angle now and the damper will move at a different velocity too.

[Le_Fromage_Grande]

The shock top mount needs bracing

[KungFooBob]

There's a pair of these BSK Speedworks bikes race in the B.E.A.R's with BHR.



They go quite well.

https://www.bskspeedworks.co.uk/

[demographic]

Aye, their top shock mounts are better braced and damn nearly at the stronger tube node/joint.

[Mr. Dazzle]

In these kind of structures it's typical to join stuff at the corners so it remains a pin jointed structure. A pin jointed structure only subjects the members to tension/compression (nominally anyway) and is usually stiffer and stronger as a result. It's so called because if you took all the welds and replaced with just pins that were free to rotate the stiffness/strength wouldn't change.

Massive generalisation but that's the idea. That's why you generally see all the big bits joined only at the corners.