stronger BMX frame- cheap or expensive?

pfred_flap_disc_40_grit_4_1_2x7_8_2.jpg


flap disk on a 4.5 inch grinder would be much faster then a file Chrome is super hard while the copper is soft will clog up a file
 
Good idea, and yeah I forgot about the hardness of the chrome. I usually use a grinding wheel, but I want this bike to be nice and pretty :giggle: I think I have a few of those wheels lying around
 
But if you guys don't think this frame will hold up for long then I'll mount the motor on it temporarily, then once I have all the bugs worked out I'll saw off the motor and put it on a more expensive bike.

I've already spent $250 on this bike, which is ALOT of $ IMO; and I got the bike for free. But most of the parts I've bought can be used over and over for decades in all my different projects, if something ends up going wrong with this bike. But if I buy an expensive BMX frame and weld/braze all over it, then find out it's too unstable at speed or something, then Ive just ruined an expensive frame and lost all of that money I just spent on it
 
meh. ill accept that. anytime i do a quick tack near a dropout its brazed, but, just to prove myself wrong, i had a squiz at my frame pile. 5 of 6 bmx frames were welded there. all bar one mtb and racer frame was brazed. pays to keep quiet :giggle:

250 is a lot right now, but compared to a new norton with a rotary...cheap as chips :) if the money goes on tools, good. if it goes on macdonalds...get rid of the engine!


maybe... get the intended frame. try loading it up with the intended weight in the right areas. yes, i suggest zip tying bricks and sash weights to your bike :) see how it rolls...


or...find a frame you like... block it up at the axles and BB etc, make a jig, and then build the frame around the engine. as long as you retain the ideal geometry...
 
you might just want to stop and think what is a serious suggestion and whats just being silly...

notice this guy doesnt incorporate any way to change, say...a tyre. they just look pretty cool. could be the way to trial a quick mock up version before cutting and welding... still, not overly practical as such...

most carbon fibre frames are designed to be working at the limits of the material. most carbon fibre frames use complex shapes that arent the easiest to create in any other material whilst retaining the strength to weight ratio.

most carbon fibre frames cost more than the average joe cares to spend.

i say most, not ALL. i can think of a bamboo bike that costs more than some CF frames...

im more than aware of how plies work, thankyou. the benefits of tube over bar, even. whoop. bamboo again. excuse me, im off with the birds... :giggle:

the thread and fabric is fairly cheap, nonetheless, and theres a variety of bonding agents available... if thats your cup of tea.

can you tell me what carbon fibre does in an induction coil at 15 Kw?

all frame builders use a jig. now thats a serious suggestion.

personally i feel it would be easier assembling all the parts on a jig, and filling in the dots with new steel tubing rather than stuff around with all the annoying features of an existing frame with tubes just where they shouldnt be, but thats just me...

any more facetious comments?

really, all that matters is that this guy is strapping a km48 rotary into his pushy :)

keaton, whats the box off? going to be chain drive to the crank i take it? then feed through a ...five? speed box...neat :)

could you hack the whole crank case off and run chain straight to the boxes primary?

if the crank has a gear on the primary... and spins "forwards", flipping the engine round, and running chain redux straight to the box would give the reversal the gear other wise provides.

just an idea.


im waiting for that to be shot down in flames too :) i probably have no idea about rotary engines, either :giggle:

 
http://www.fibreglast.com/product/1...abric-2365/carbon-fiber-fabric-classic-styles
average of 3 or more yards are used


yeah really cheap..
plus the epoxy resin to do CF is $200 a gallon on average
now a factory built CF framed recumbent is $5000 or more so it it's cheaper to build one but being the huffy frame he wants to use was a less then $200 bicycle...

as far as shaping pink styrofoam is used quite a bit to make custom frame recumbent bicycles
20130408_054209_zps53697797.jpg

complex enough shape for you?

and Norton stopped making motorcycles in the 1970s
 
whatever. sorry. a refurbished norton.

back to the OP and subjects directly relating to the OP...

HeadSmess said:
personally i feel it would be easier assembling all the parts on a jig, and filling in the dots with new steel tubing rather than stuff around with all the annoying features of an existing frame with tubes just where they shouldnt be, but thats just me...



really, all that matters is that this guy is strapping a km48 rotary into his pushy :)

keaton, whats the box off? going to be chain drive to the crank i take it? then feed through a ...five? speed box...neat :)

could you hack the whole crank case off and run chain straight to the boxes primary?

if the crank has a gear on the primary... and spins "forwards", flipping the engine round, and running chain redux straight to the box would give the reversal the gear other wise provides.

just an idea.
Click to expand...

assuming as it is, the km48 shaft on the left, drive to crank, and crank drives gearbox on the right, as per standard( for the pundit i better mention harley which is on the left or maybe even kawasaki with a primary chain drive)

so, rotate km48, shafts on right hand side, should be spinning the right way too...


and have you got the thing up and running yet? video :)
 
HeadSmess said:
whatever. sorry. a refurbished norton.

back to the OP and subjects directly relating to the OP...



assuming as it is, the km48 shaft on the left, drive to crank, and crank drives gearbox on the right, as per standard( for the pundit i better mention harley which is on the left or maybe even kawasaki with a primary chain drive)

so, rotate km48, shafts on right hand side, should be spinning the right way too...


and have you got the thing up and running yet? video :)
Click to expand...

I haven't got it running yet, I'm still waiting to get some apex seal springs in the mail (didn't want to risk it with homemade springs and have the tension wrong).
Also, I can't start the engine till it's in the bike. Cuz my ignition is a weed wacker bottom end and flywheel, with a 4 stroke ignition coil atatched, that's going to have it's crank welded to the left side of the e-shaft (and yes, I ground off the counterweights lol). Therefore I can manually adjust the ignition on the flu until I find the sweet spot (just manually rotate the bottom end to change the timing. I'll have a bracket with long slits in it, that the lower end can be bolted in place to, so the bottom end can be rotated and then cranked down onto the bracket when the timing is set. It's hard to explain, I can post a drawing if you want.

The box is off a beat up 89 Kawi kd80x with a blown back tire (burnout), no spark, seized forks, etc.(a rare bike, parts are impossible to get). I bought it off a friend's dad, he wanted $100 for the whole bike, and wouldn't sell just the motor for any less. And there was no chance my parents would let be being home a complete bike, so I was sorta stuck and had to buy just the motor for $100. Still a better deal than getting a box off ebay, cuz this comes with a top end, 2 new wiseco pistons, a carb, expansion chamber, etc. The friends dad agreed to let me keep the bike frame at their place until I sell it for 20$ or something.:cool:
It's a 5 speed, 1 down 4 up.

The actual gears are in mint condition, but the actual engine was completely done for. Crank was full of water and the bearings had 1mm of play, big end and wrist pin are pitted beyond belief (good thing I'm not using most of those parts).

The output sprocket will be on the crank, on the magneto side of the case, and I'll be cutting a big hole for the chain to run out of. I'm not actually using the crank because I didn't want to have to grind off the counterweights to balance it. (I have no way to balance test it anyways). The crank bearing ID is a wierd side, somewhere between 3/4" and 13/16". However I managed to find a shaft that fits the bearings fine, it's a gearshaft from that rm125 case I got (which was missing more than half of the parts, but was supposed to be complete).

And I'm just beginning to get into the wierd things about this build, have I mentioned turning down the massive cast steel flywheel on a lathe to make the engine fit in the frame correctly? Yeah, I knew this means having no more counterweight on the flywheel, so I need to build a homemade adjustable counterweight, and experiment with adding washers until it stops vibrating :giggle: that old flywheel was too heavy anyways.
But seriously, every part that isn't homemade is modified somehow. When I make a build thread when it's done, the explanation of how it works will take me days to type lol. A lot of that being from my homemade v-tec of sorts with 3 adjustable weedeater carbs, and 1 being used at low rpm, but the others activating only at high rpm:helmet:
I can't wait to see the dyno numbers, with this plus tons other crazy mods I'm doing!

The engine's shaft'll be sticking out the left side. Otherwise it would be spinning backwards (unless I drive it off the fan side of the crank)

I'm contemplating making a custom frame with thick (like 3/8" thick) wall pipes, but getting all the parts aligned and mitered properly would be a huge pain. 1mm change in the position of the headtube and the angle is affected by a lot of degrees, and any side to side misalignment and the headtube is being twisted side to side too
 
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