Extending shock mounts?

[ruffle]

Another engineering/modification question (can you tell I'm project planning? )

If the mounting points on a swinging arm are significantly wider than those on the frame (I'm talking ZRX1200 arm and Z1000J frame) is there any sane way of extending the top mounts?

Would an extension that screws onto the existing mount and a spacer between the shock and the frame be a sensible way of doing it? or would I have to cut out the existing mounts and replace them with sommat longer?

TIA

[KWACKERZ1]

Both options have been done on projects on this site.

PMC do a set of extenders ready made, z-power can probably get them for you.

[ruffle]

I did try searching the forum and googling but didn't find anything definitive.

But thanks for the pointer - knowing it can be done is 90% of the battle. Off to search for
the PMC ones.

[ruffle]

Hmmmm.... not found the PMC ones yet (although they do mention that you need them when using their braced swinging arm) but I did find these:

http://www.ebay.com/itm/2808039



which just look weird and wrong to me.

[z1bman]

http://japan.webike.net/preview/info/p3 ... 82059.html

[LondonZ1]

Here's a photo of my Z900 frame with the PMC shock mounts tack welded in place. You can also see the original (now redundant) higher mounts. By using the PMC mounts you get both wider mounts and a less vertical shock angle. You'll need to make sure that the PMC mounts are the right width for your swingarm.
Also, Harris (who did all the mods) were concerned that the new PMC mount was in the middle of a fame tube and so they made and welded in a stiffening plate to support the new mount.
The simple answer is that it's all possible but you need to careful to get the dimensions right. Personally I would relocate the upper shock mounts as I have done as it will be both stiffer and look better.
You'll then need to source a shock with a suitable length and spring rate.
All this is based on my experience with a Z900 frame; the Z1000J might be different.

[KWACKERZ1]

http://www.z1ownersclub.co.uk/forum/viewtopic.php?t=853

ChrisNI's modified z1000 project shows how to do it in detail.

This may help.

[ruffle]

Rather than installing new mounts I was thinking more of extending the existing ones.

Rough measurements with a tape measure suggest that I need to space out the shock top mount by 26mm each side but I need to do some 'proper' measurements and the length of the spacer and extension in the drawing is therefore not to scale.

'Scuse the drawing; last did any technical drawing in school with a quill pen and gas lighting



Option A allows the fitting of a normal domed nut but I don't really like it as there's an obvious weak point.

Option B has the same weak point as A.

Option C reduces the weak point (I think) as the Socket Screw goes into the existing mount. If I use an M8 grade 8.8 or 12.9 the shear strength is measured in tonnes (if I've googled correctly). The mount can be drilled and tapped by using the extension bitty as a drilling/tapping guide.

This 'bolt on' solution also appeals as I can make the above in my lathe but my welding skills are dire

However, I'm a software engineer not a real one so opinions of those wot know about these things are most gratefully received.

[zed1015]

I would possibly go with 'C' but incorperate the spacer as in 'A' so the whole thing is in one piece which will increase the overall strength and spread the load over the maximum area.

[ruffle]

Aha! Ta Muchly. You mean like option D below?



Option E (drilling all the way through) did occur to me but I think there's too much potential for the drill wandering (it would be a handheld drill) so Option D looks like the favorite.

EN1A steel be OK do you think?

[harrythemagnum]

From another post, I was looking to make up some shock extensions for another member, the ones on my bike are similar to option A, initially looking at the drawing was concerned I had made something unsafe.

But help me out here, isn't the shock force still acting on the original mount, granted on the end with a sleeve over the threads, the extended thread is only for the nut to stop the shock sliding off, I don't think I would risk a carry rack but a grab rail should be ok?

Your thoughts before I carry on.

[garyd]

Purely from an uneducated view...

I very much doubt that anything would shear.

But there is obviously an increase in load at the point where it meets the frame purely due to force being applied further away along the same size bar.

But as I've never heard of these mounts ever giving any trouble...even in crashes, I'd suspect the extra load is within safe parameters.


Any professional mathematicians care to work out some moments of force?

[Padders]

Option A would be fine for me no worries

[PJ]

Option A would be fine for me no worries

And me