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Old 07-09-17, 09:09 PM   #231
Craigg
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Default Re: SVBMX Build Thread

Is the stock swing arm going to be rigid enough for that? might want to add some bracing underneath? (like an upside down Bandit 1200)
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Old 07-09-17, 10:02 PM   #232
Trev B
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Default Re: SVBMX Build Thread

How about a nice single sided swing arm
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Old 08-09-17, 12:48 AM   #233
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Default Re: SVBMX Build Thread (99 SV650)

This is very interesting and it's really good to see you pushing the envelope with the humble SV650.
You have pulled off a stunner with the home built fairing aswell.

Making mechanical modifications that look good is far easier than aesthetic alterations like fairings, bodywork etc.

You're fairing is very elegant, and the way you have encompassed hard edged lines to the SV, which is a very rounded off aesthetic design is truly an achievement.

Your alternative shock arrangement is going to add a heavy component to the unsprung weight though. Even though the linkage arrangement could be worked out to give any wheel rate desired the addition of any unsprung weight is a step backwards in my opinion. Especially considering it is purely for aesthetic reasons of exhaust repositioning.

It will also place a relatively heavy single component further away from the C of G which gets us away from the mass centralization mantra which works so effectively on bikes.

I included two pics of a transversely mounted shock on a purpose built special. It might serve you better if it can free up some space to reroute the exhaust to where you want.

Either way I'll be watching with interest.

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Old 08-09-17, 08:11 AM   #234
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Default Re: SVBMX Build Thread (99 SV650)

Quote:
Originally Posted by Craigg View Post
Is the stock swing arm going to be rigid enough for that? might want to add some bracing underneath? (like an upside down Bandit 1200)
Unsure! But if it feels like it need bracing il do that too.

Quote:
Originally Posted by Trev B View Post
How about a nice single sided swing arm
Seen a few curvys with a sssa, not too keen.

Quote:
Originally Posted by rabbit8dude View Post
This is very interesting and it's really good to see you pushing the envelope with the humble SV650.
You have pulled off a stunner with the home built fairing aswell.

Making mechanical modifications that look good is far easier than aesthetic alterations like fairings, bodywork etc.

You're fairing is very elegant, and the way you have encompassed hard edged lines to the SV, which is a very rounded off aesthetic design is truly an achievement.

Your alternative shock arrangement is going to add a heavy component to the unsprung weight though. Even though the linkage arrangement could be worked out to give any wheel rate desired the addition of any unsprung weight is a step backwards in my opinion. Especially considering it is purely for aesthetic reasons of exhaust repositioning.

It will also place a relatively heavy single component further away from the C of G which gets us away from the mass centralization mantra which works so effectively on bikes.

I included two pics of a transversely mounted shock on a purpose built special. It might serve you better if it can free up some space to reroute the exhaust to where you want.
Thanks for the kind comments and concern. I like the idea of that transversely mounted shock but i dont think there's a good position on the sv for such a setup. I also concidered a buell style pull shock mounted under the engine but it would require mouting one end off of the block itself and i dont like the idea of that either. I thought about a twin shock setup too, mounted direct from swingarm to subframe. Bit old skool! But i like the openness/gap between tail and wheel and that would encroach on that space, although it would free up the space for exhaust.

I understand my design would add weight, and i agree it would be a problem if my tail end was stock, but as it's not i feel it will be ok.

My new subframe, seat, cowl, undertray, light, indicators and plate all weighed less that the stock subframe alone! Not to mention the weight of the plastics, seats, lights etc that make up the complete stock tail! Also the massive lump of weight that is the stock exhaust! The weight saved from that alone will likely cover the additional weight of the mech at the rear.

That all being said, it could make the bike ride like s**t! I guess the proof is in the pudding. For me, this is just another project. I saw a similar setup on a bmw and thought "that looks pretty damn cool", so figured i could give it a go. And the fact it would allow for the exhaust setup i want is a bonus.

Also, the plan is to make the mech with the use of a upgrade sv Nitron shock, so if all goes to s**t i can still use it in its stock position.
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Old 08-09-17, 09:40 AM   #235
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Default Re: SVBMX Build Thread (99 SV650)

I looked at the model you posted a bit closer and can see your rationale a bit more.
You've planned ahead to use an off the shelf shock to suit the SV so a backup strategy is a smart move.

Unsprung weight as you probably know is the mass not supported by the springs. It's the mass that has to move up and down to follow the road contour.
The lighter this mass the less inertia and the more responsive the suspension can be.
Not all the swingarm will be unsprung mass the same as not all your suspension system will be either so with carefull design it probably won't be as detrimental as I first thought.

I also had a look at my SV and I can see that a transversely mounted shock would have to be quite short and a bespoke item. So your plan is good in that respect.

You are probably still working out the details but what are you going to do to the frame to pivot the linkage? It appears
you currently have it pivoting on the r/h lower subframe lug of the stock frame.
Is the whole subframe going to be braced to spread the load over all four mounts? Or are you going to weld a beefier lug to the frame?

And last question, are you doing any finite element analysis?

Anyway crack on. This makes a refreshing change from "I just fitted some LED blinkers and now they don't work" type of threads😁

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Old 08-09-17, 12:18 PM   #236
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Default Re: SVBMX Build Thread

I'm not too sure about unsprung weight and all the rest of it! I've just got an idea which will either work or wont work :S I'm just gonna build it, bolt it on an see. If it works.. great, if not.. so be it.

All i know is, I've designed the mech to give the same range of movement from the swingarm/shock as per the stock setup. I basically strapped down my rear end as much as i could (more than i expect i could get it to compress on the road), measured the angle change (swingarm) and the shock compression (mm) compared to its uncompressed/unweighted (riderless) state. I then set my solidworks model to the same 2 states and modified my mech untill i was getting the same amount of shock compression in both measured states.

I'm therefore hoping the bike wont handle much differently than what is does now. Actually, hopefully better with an upgraded shock!

With regards to the pivot point, yes il be pivoting on the r/h lower lug. I dont feel like this will need any further reinforcing. I say this because i feel like my subframe is strong enough to share the extra stress on the lug.



The entire mech will be made from aluminium except for bearings, nuts and bolts. The main arm will be 30mm thick (2 x 15mm bolted together) and the pivot plates (triangles) 12mm thick. All pivot points will be use a 10mm partially threaded bolt/axle. And all nuts will have a nyloc insert.
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Old 10-09-17, 04:14 AM   #237
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Default Re: SVBMX Build Thread (99 SV650)

I see you posted that your a design engineer so I don't need to tell you anything about structual design failures but I'm not convinced that the rear lower subframe mount would be strong enough to take the loads your going to be asking of it. Of course I'm just eyeball engineering it so that's not very scientific in itself.
I'm just comparing it to the oem lugs cast into the frame and swingarm.
The loads are quite high compared to most other areas on the chassis.
What scares me is cast alluminium frame sections aren't very forgiving in failure like mild steel.
Mild steel will enongate, deform and at least give you some indication that complete failure is around the corner.
Cast alloys just fracture.
I'm sure the safety factors are quite high for production motorcycles and eating in to that I'm ok with if the use of the end product is more closely known.
Personally I would be bracing the subframe to spread the load across the subframe to allow the four mounts to share the load.
I say all this because it would be a sad thing to hear of a subsequent failure and injury to yourself, and also hoping to learn something from yourself whom is pushing the boundaries and has technical abilities I don't ie. Engineering design calculations.

I did some real quick arithmetic (not my strong point) and a 9.5kg/mm spring at full bump of 65mm (shock stroke) will take 617kg of mass to keep it bottomed out. So over 1/2 a ton of force which is quite significant. I hope you get what I'm talking about and don't take me as a condescending *****, a common criticism leveled at me!....

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Old 11-09-17, 06:47 AM   #238
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Default Re: SVBMX Build Thread

Don't worry about it... I'm not
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