Swing-Arm Bobbins

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legendlives
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Swing-Arm Bobbins

Post by legendlives »

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

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.
I like my bikes like my women - Loud with two big cylinders :D
NZSpokes
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Re: Swing-Arm Bobbins

Post by 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.
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legendlives
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Re: Swing-Arm Bobbins

Post by legendlives »

Now have the full 'bafflectomy'. Sounds great and not too loud.
I like my bikes like my women - Loud with two big cylinders :D
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sirch345
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Re: Swing-Arm Bobbins

Post by 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
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Re: Swing-Arm Bobbins

Post by OldFart »

How deep did you drill the hole, as that would be helpful. many thanks
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legendlives
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Re: Swing-Arm Bobbins

Post by legendlives »

OldFart wrote: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.
I like my bikes like my women - Loud with two big cylinders :D
tony.mon
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Re: Swing-Arm Bobbins

Post by 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.
It's not falling off, it's an upgrade opportunity.
NZSpokes
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Re: Swing-Arm Bobbins

Post by NZSpokes »

Ive done it that way for years. Its not holding that much weight.
bigr250
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Re: Swing-Arm Bobbins

Post by bigr250 »

tony.mon wrote: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!!!! :cry: :cry:
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Kev L
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Re: Swing-Arm Bobbins

Post by Kev L »

I went with welded on blocks to locate the bobbins on mine :thumbup:
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Watty
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Re: Swing-Arm Bobbins

Post by Watty »

Kev L wrote:I went with welded on blocks to locate the bobbins on mine :thumbup:
Same here Mr Kev Mc king blue :thumbup:
SH#T HAPPENS!!!!!!!!
bigr250
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Re: Swing-Arm Bobbins

Post by 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!!
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sirch345
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Re: Swing-Arm Bobbins

Post by sirch345 »

bigr250 wrote: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
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Re: Swing-Arm Bobbins

Post by 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 :D 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.
It's not falling off, it's an upgrade opportunity.
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eezee29
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Re: Swing-Arm Bobbins

Post by eezee29 »

anyone with with close-up pics/dimension of the alloy block?
trying very hard to get over the 50 posts hurdle :lol:
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