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Suspension Suspension and Handling Forum - bouncy bouncy!


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October 1st, 2010, 02:55 PM   #1
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Bushmechanic frame Build pics and Stuff

some of the ideas in here viewtopic.php?f=8&t=13017 need to be tested

the pics still truncate, you can open the links below to see more

frame design looks easy in photoshop



adjustable mythbusters "Adams rig" style to check geometry



another jig to hold the head still and locate shock mount while I cut out the heavy mid section

Attached Images
File Type: jpg photoshop chop.jpg (498.9 KB, 7 views)
File Type: jpg adjustable geometry.jpg (438.8 KB, 6 views)
File Type: jpg frame 001.jpg (419.8 KB, 6 views)
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October 1st, 2010, 03:09 PM   #2
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Re: Bushmechanic frame Build pics and Stuff

mid section removed, weighs about 7 kgs



putting stuff back in, idea is to add less than I removed



all tacked up so check alignment and angles before welding . checking the alignment and deciding what to do are the tricky bits, just making the thing is fast by comparison



total weight is 6kgs so far but another 3 or 4 still left to add. FWIW the stock subframe weighs 2kgs

the twin tube or perimiter design is NOT the lightest strongest or cleverest way to build a frame becasue the 2x 1" tubes weigh the same as a single 2" centre spar and Im still to add another 2 sets of tubes to triangulate it

the advantage of the perimiter setup is you have more room for a forward mount air filter if you wanted one and the tanks don't have to be load bearing. every bike ive had with a tank you sit on has eventually given me grief in some way or another. so the choice is between a heavy loadbearing tank thats a PITA to make or a heavy perimeiter frame to protect some lightweight tanks. the perimiter frame can also be stiffer torsionally if that were an advantage.

so with the hindsights switched on the easiest way to lighten a stock frame is to cut out the airbox and replace it with a damaged 48mm fork lower tube. I'm mostly doing this to change the geometry and get betterer ergonomicals, it will still be lighter than stock but a single spar frame could be 2-3 kgs lighter again.

more botching pics soon
Attached Images
File Type: jpg cut.jpg (540.0 KB, 5 views)
File Type: jpg jig.jpg (552.9 KB, 5 views)
File Type: jpg frame 012.jpg (642.1 KB, 5 views)
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October 2nd, 2010, 12:02 AM   #3
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Re: Bushmechanic frame Build pics and Stuff

Strewth Ruth.
Now I have seen it all, a Husachopper.
Probly just the perpective photo taken from but it looks like a big gap between top of motor and headstock. should make it nice and steady but how many inches over are the forks gunna hafta be lol.
But seriously, You must have a set of clamps with plenty of offset there brother.

I take my hat off to you bushie.
I have cut up a cuple of frames it the past and modified things but by sorting out one issue I created others in other areas. I gave up and bought a proper bike to start with (me berg.) Maybe one day when time, money, motivation and patiance allows I try again....... Nah ill just enjoy other peoples labours.
Keep up the good work Bushie, yor an inspiration.
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October 2nd, 2010, 02:56 AM   #4
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Re: Bushmechanic frame Build pics and Stuff

seen the buckets and tins of stuff he's got in his shed! they ought to call him chemical ali !!!

regards

taffy
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October 2nd, 2010, 06:35 AM   #5
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Re: Bushmechanic frame Build pics and Stuff

Twas wondering if the products had been carfully placed in the background for the photos or pure coincedence?
Gotta love the special race gas alongside the special race oil!
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October 2nd, 2010, 02:01 PM   #6
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Re: Bushmechanic frame Build pics and Stuff

tis a long way from the front wheel to the engine

the "problem" starts with the output shaft location in the cases, its 40mm to low so in order to lower the COG without ruining the swingarm angle I had to cant the engine forward. then if i want 28 - 30 deg rake the headstock needs to be right where it is or the wheel hits the frame. the once piece radiator makes this about 30mm "worse" than a 2 radiator setup.

its about 50mm further from the front wheel to the COM than I had before which is about 50mm further than stock. that 50mm extension was an improvement, 100mm further than stock may make it hard to turn but then I'll just make the swingarm longer. the idea is not really to increase stability its mass centralisation lower COG and increasing the trail for sand. the new bergs have an extra 160mm between the wheel and the crank...........

from what ive seen shorter bikes don't nescesarilly turn any better 3rd gear and above, the hayabusa hillclimber in my gallery has a 1700mm wheelbase.

my berg at 1520mm wheel base is 30-40mm longer but still has higher front wheel loading than the japper MX bikes and still turns inside them.

not sure what will really work in the end but its fun this stuff. the film on any sunday sublty points out that a great deal of the enjoyment of motorcycling can be found in tinkering, working on and improving the bike. its sad to see how many dirtbike riders miss out on that bit.

30% off sale on chemical alis argon racegas and special 5 viscosity blend red bottle forker oil
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October 3rd, 2010, 07:29 PM   #7
 
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Re: Bushmechanic frame Build pics and Stuff

it's really hard to say what will work & what won't bushy,thats for sure
I see the logic in what you are doing,for the outcome you want.
i'm sure you will get a reasonble good outcome eventually,its just trial & error really.
I still can't get my head around this high output shaft & swingarm angle?dunno,not convinced
personally, i like yamaha's idea of low crank & gearbox height for a low c.o.g ,then the barrel & head on a lean back to get weight central.
probably the only problem i can see is, with getting that output so high,the engine has to be leant forward,which spreads the weight along the wheel base of the bike.this is opposite to the modern day theory of gettting all those extra kilo's in the centre of the wheelbase or the turning pivot point of the bike.the more weight that is either side of the pivot(forward/back) the slower it will turn.whats good for one thing maybe not be good for another.
not much you can do about that though using this motor.
10 out of 10 for trying.in no way am i trying to be a wet blanket on your project bushy.no way,i'm just looking at your project from a different slant.
do what you think then test it.
..weed..
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October 3rd, 2010, 11:35 PM   #8
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Re: Bushmechanic frame Build pics and Stuff

personally, i like yamaha's idea of low crank & gearbox height for a low c.o.g ,then the barrel & head on a lean back to get weight central.
me too, if the dreaded husaberg mains would fail or even just look a little tiny bit worn Id make my own set of cases with bigger mains, the crank down low output shaft up high and the cylinder leaned back, would be BT i reckon.
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October 4th, 2010, 11:52 AM   #9
 
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Re: Bushmechanic frame Build pics and Stuff

Originally Posted by bushmechanic
...the crank down low output shaft up high and the cylinder leaned back...
You'd end up with the output shaft on the cylinder head...
Can just as well put the gear box there too, all power going via the cam chain.
Its what we alla re going to have in 20 years I guess...
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October 4th, 2010, 03:45 PM   #10
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Re: Bushmechanic frame Build pics and Stuff

or we could spin the engine 90 deg in the hrozontal plane use a Guzzi style carbon driveshaft instead of a drivechain

should be able to put the crank well back
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October 5th, 2010, 01:11 AM   #11
 
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Re: Bushmechanic frame Build pics and Stuff

bloody briliant idea bushy.
that output shaft coming out the wrong way is the sticker though
i can't really see how you could get that to work.?but you are better than i.
what about just moving the motor back,so the motor weight is more central to the centre of wheelbase?
maybe,forget the swingarm pivot through the motor/frame where it is& mount it up higher in the frame? nah that won't work,the output shaft has to come up the same as the swingarm
then again,just another thought ,if you want this better swing arm angle,mount the motor central to the wheel base,then & up.i think it was only like 40mm higher you wanted?
even at 40mm higher,it won't be as top heavy as the slant motor bergs & the motor weight is central.
dunno lad just a couple of rammbling thoughts as i hit the "been drinking button again"
..cheers..weed..
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October 5th, 2010, 03:14 AM   #12
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Re: Bushmechanic frame Build pics and Stuff

all good ideas great stuff lads ideas are cheap chromoly tube is not

next bike I build will be more conventional ; the old burnt 550 engine with lightened crank, angular contact mains estart and in an 85 bigwheel chassis, perfect tight track enduro weapon for a light rider.

pretty sure this big one is gonna work fine though, the wheel 100mm forward from stock puts the engine closer to the geometrical centre of the bike, well the engine stays put but the geometrical centre moves.

downside is perhaps not enough weight on the front but the engine is canted forward, its not much really, the front of the rocker cover is only 15mm further forward. so both concerns work together really and with a nicer seat ill be able to get my weight 200mm further forward on corner entry.

almost got another 3/4" tube fitted today after work, blasted work
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October 5th, 2010, 03:29 AM   #13
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Re: Bushmechanic frame Build pics and Stuff

what is to stop you having an extended headstock with the front wheel where you want it but with the rake steepened? I realise that this may puncture your sand plans .. but will it?

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October 5th, 2010, 03:40 AM   #14
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Re: Bushmechanic frame Build pics and Stuff

ahh.... well see the front wheel is where I want it

everyone else wants me to have it closer to the engine. if I wanted to do that I could easily have picked up a rolling jap chassis cheap and just squeezed my engine in like enginehardware did.

the other way to do this is like Taffy hints at is steeper rake and reduced offset or simply go this way and extend the swingarm if needed
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October 5th, 2010, 06:44 AM   #15
 
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Re: Bushmechanic frame Build pics and Stuff

Originally Posted by bushmechanic
next bike I build will be more conventional ; the old burnt 550 engine with lightened crank, angular contact mains estart and in an 85 bigwheel chassis, perfect tight track enduro weapon for a light rider.
You mean something like this??? Montesa 4RT motor in an HM Honda 50 enduro chassis.
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