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Old Yesterday, 12:19 AM   #1
Rockfox OP
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Joined: Mar 2013
Location: Western Cape, South Africa
Oddometer: 6
Amagaeza Rally Bike Build

Firstly the Amageza Rally is a navigational cross country rally spanning 7 days and 2500 miles in and around South Africa and Botswana. it is modeled on the Dakar and other similar events.

Ok,
now we have gone completely mad. This picture is the (incomplete) prototype frame for our Rally bike.

The geometry etc etc are designed with enduro suspension geometry and checked with Solidworks. We opted for a semi stressed engine to reduce frame complexity with required frame rigidity. We then built a 'concept frame' to evaluate the spring rates in real life. (Static loading only.)

Next step will be to make the changes to the design as some engine/frame clearances were too tight or non existent once the wiring harness will be plugged in.

Just a few of the design criteria.
1. Centre of Gravity as low as possible.
2. Access to plugs etc within 2 minutes if bike drowned.
3. Access to valve adjustment within 2 minutes (tappet cover removal)
4. Larger water radiator.
5. Oil cooler with extra oil capacity. (It is a dry sump motor)
6. Air filter access within 1 minute.
7. Balanced fuel load between front and rear tanks.
8. Hydraulic clutch actuation (Still under investigation)
9. All fuel tanks and body panels from high impact flexible epoxy resin.
10. 300mm suspension travel, 350mm ground clearance,
11. Less than 145kg dry weight in full rallye kit. 65F/75R weight balance.
12. 30l fuel split in 18 rear 2x6 front.
13. Aluminium rear subframe.
14. Custom exhaust pipe and muffler.
bla.. bla .. bla.

The next build phase will be to manufacture the 'real' frame and then complete the basic running gear as a 'Plastic' so it can be tested at Dirt and Dust and Zone7 or Quarry for sand. The rear shock angle will be adjustable during shakedown tests to test the 'linear' spring rate during compression with a standard spring. We might need to go 'progressive' to simulate the effect of a link suspension design to achieve the 'winding up' of the suspension over the last 100mm of wheel travel.

NOTE: all the braces etc not welded in as this phase was to evaluate the suspension geometry.

Mike
www.rockfox.co.za

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Old Yesterday, 01:38 AM   #2
mousitsas
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very nice!

One comment if I may...If you fit a progressive spring then you will need a progressive dampening shock too. One without the other will probably yield an iffy behaviour. I would go with a linear spring and simulate a linked suspension by playing just with the shock angle. Otherwise, why not borrowing a linkage system off an other bike? Something like a drz for example.

edit. Just realised that you have already chosen a swingarm, so the last suggestion is not aplicable.
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Old Yesterday, 03:26 AM   #3
GezwindeSpoed
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This is not just a rally bike build, but first a bike build! Looking forward to your progress.
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Old Yesterday, 05:01 PM   #4
TobyG
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Looking great, I'll sure be following this one!
My 650GS is still hella heavy compared to what you want to achieve!
(~ 165kg without fuel and once the aluminium swingarm is mounted, of course the Rally tanks and nav gear would easily add another 10 to 15kg to that)

But I guess you won't use much more than the swingarm and the engine from the 650GS?
One important note when you're using this swingarm as-is: Replace the nuts on the chain tensioner bolts with nyloc nuts!


This is mine, by the way, the bike was already completely modified when I bought it,
I just put in a lot more work to make it the perfect travel/enduro hybrid for my needs.
Still using the BMW main frame, engine (with slight modifications, now power mods, though) and currently the swingarm,
everything else is either custom or aftermarket parts.
I did recently start outfitting all the fairing with 1/4 turn fasteners, so I can access the valve cover and all other essential parts (electrics,
injection unit, ECU, battery etc.) real quick, too.


http://i.imgur.com/x0wZxC2m.jpg

And this is the swingarm that will go on it, soon:


http://i.imgur.com/EyRQza1.jpg

[click the links for higher resolution]



Really looking forward to your progress on this build!
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Old Yesterday, 11:01 PM   #5
Rockfox OP
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Location: Western Cape, South Africa
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Toby G Swing arms

hi Toby,

Thant 650 really looks like it means business.

Quick question what swingarm arm is that. from which bike and is it fully aluminium?

Thanks
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Old Today, 07:52 AM   #6
TobyG
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Quote:
Originally Posted by Rockfox View Post
Quick question what swingarm arm is that. from which bike and is it fully aluminium?
It is fully aluminium, cast aluminium front with 2 profiles welded to it.
Unfortunately, though, they are rare as hens teeth.

They were made by Touratech for the F650GS, to allow for better fitment of an 18" wheel and mounting a longer shock (+30mm suspension travel at the wheel), but only a handful (less than 10 are known to still be in use today) were ever sold.
Took me 2 years and a good portion of luck to find one to purchase.




Just remembered there was another extreme 650 conversion by an italian BMW motorcycle dealer,
they also modified or replaced pretty much everything other the main frame and swingarm (carbon underseat tank and the bike has been equipped with a carburetor, afaik).

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Old Today, 10:12 AM   #7
DirtyDog
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Twofer, and I'm in on the ground floor.

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