Swing-Arm Bobbins

[legendlives]

I've been asked to detail the fitting of my new swing-arm bobbins:


So in detail, the holes are drilled 95mm from the end of the swing arm and 60mm down from the top.
Centre punch, drilled small guide-holes, then drilled 7mm hole.
Tapped hole M8 and screwed in Bobbins.
Voila!

I went for the 8mm bolts as I didn't want to trust my bike with the 6mm ones on offer.

[NZSpokes]

I did the same with my current swingarm. Im about to get a Braced one welded up so will weld on proper bobbin mounts to it.

[legendlives]

Now have the full 'bafflectomy'. Sounds great and not too loud.

[sirch345]

I did the same although I used the measurements suggested by a member on the Superhawk forum, they were 25mm up from the bottom and 107mm in from the end,

Chris.

[OldFart]

How deep did you drill the hole, as that would be helpful. many thanks

[legendlives]

How deep did you drill the hole, as that would be helpful. many thanks

The hole goes straight through the walls of the swing-arm. Wall thickness is only about 4mm.

[tony.mon]

Which is why I recommend using a metric fine thread tap and bolt.
More threads in that thin section.

You could always use a nutsert.

But I haven't heard of any failing, so even a standard pitch thread seems to hold ok.

[NZSpokes]

Ive done it that way for years. Its not holding that much weight.

[bigr250]

Which is why I recommend using a metric fine thread tap and bolt.
More threads in that thin section.

You could always use a nutsert.

But I haven't heard of any failing, so even a standard pitch thread seems to hold ok.

Just been looking at this as I'll be fitting bobbins to my arm, I'll be going a 'different route' & welding a piece of 12mm ali bar with an M8 thread underneath the arm. I'd be cautious with the above method as metric fine has a 1m pitch so at best only 4 threads in a 4m arm, I've just measured a 'rivnut' and the threaded section is about 10mm.
I don't think either is an ideal solution but if your only going to use a paddock stand for a tyre change once a year either would suffice. If your bike is to be used for racing/trackday's where paddock stands will be used regularly and the bike might be traveling in a van on a paddock stand I'd go for something more structural or you might just open your van to find your pride & joy leaning against the side of the van!!!!

[Kev L]

I went with welded on blocks to locate the bobbins on mine

[Watty]

I went with welded on blocks to locate the bobbins on mine

Same here Mr Kev Mc king blue

[bigr250]

Obviously a matter of personal choice.

Not to mention the availability of someone with ali welding equipment (& the skill to do a decent job!!), then you have the difficulty of welding while the arm is on the bike, so as often as not simply drilling & tapping straight into the arm is a far easier and acceptable way of fitting bobbins.

Which ever way you chose it's got to be better than using a paddock stand with those cups under the sides of the swingarm!!

[sirch345]

Obviously a matter of personal choice.

Not to mention the availability of someone with ali welding equipment (& the skill to do a decent job!!), then you have the difficulty of welding while the arm is on the bike, so as often as not simply drilling & tapping straight into the arm is a far easier and acceptable way of fitting bobbins.

Which ever way you chose it's got to be better than using a paddock stand with those cups under the sides of the swingarm!!

Yes exactly.
If I had to do mine again, I would remove the swingarm and have alloy blocks welded underneath it rather than drilling the side-walls of the swingarm. However after saying that, I haven't had the bobbins move yet since fitting them, but I don't need to support the bike to a race track supported on them in the back of a van, so that could be a different story as you point out Ross,

Chris.

[tony.mon]

Clearly a welded-on bracket would be stronger.

However, for those who don't have that facility (of who aren't that keen on removing the swingarm to take it to a welder) I can report that I drilled and tapped years ago, then used as normal.

On and off the paddock stand more often that most, due to various bits of work over the years and strapping down in the back of a van fairly frequently- no problems at all. I used stainless M8 FINE bolts and tap, to try to ensure that as many threads as possible were in the 4mm or so of wall thickness in that area.

No movement or bending, and they're still on the arm, which is now on the back of Jonesy's bike.

I even sat on it while on the stand plenty of times, to adjust bar and lever positions, and to adjust the chain.
It was strong enough for my fairly extensive use.

One thing, though; I'd recommend keeping the bobbin as short and close to the SA as possible- the longer you make it, the more likely it will be that the bilt bends.
Bobbins with a wide base that will fit flush with the SA will be strongest.

[eezee29]

anyone with with close-up pics/dimension of the alloy block?