stronger BMX frame- cheap or expensive?

Where do you put your feet when you're riding that THING? O_O Obviously not on the pedals.. oh I think I spotted it.. over the rear axle.. that's for the rider, not a passenger, right? omg and you say this DOESN'T loop out? o_O

I have to agree with sublunacy too.. you need some proper brakes for the safety of other road users and pedestrians.. if you're not just riding this alone on private land then it's going to be a big problem if you hit someone.

and going back a bit.. The reason I mentioned seatstay in particular was that when any weld on bicycle frame cracks, that's the one tube that goes through your leg, perhaps piercing your femoral artery. The upper welds if cracked cause the frame to bend IN, the others at the bottom bend OUT from your bodyweight squashing the bike down. But looking at the pics.. I'm not sure this is your biggest concern right now. I don't want to be rude, and I know it doesn't have to be pretty; but to me that bike looks like a deathtrap.

Your new bike is going to be awesome though, I'm sure.. with a different motor and an adult bicycle frame you'll be able to make something far better. :) Now how about some pics of this rotary motor then? :D
 
Where do you put your feet when you're riding that THING? O_O Obviously not on the pedals.. oh I think I spotted it.. over the rear axle.. that's for the rider, not a passenger, right? omg and you say this DOESN'T loop out? o_O

Those foot pegs are DEFINITELY not for passengers!!! image.jpg
image.jpgnotice the awesome homemade rear foot brake lol

The bike will wheelie if I try and I'm in firs gear, but otherwise no. Because I don't put any weight on those foot pegs at all, they're just for my feet to rest on. Actually a pretty comfortable position
FurryOnTheInside said:
I have to agree with sublunacy too.. you need some proper brakes for the safety of other road users and pedestrians.. if you're not just riding this alone on private land then it's going to be a big problem if you hit someone.
I'm already changing the brakes. Dual v-brakes on each wheel, remember? :)

FurryOnTheInside said:
and going back a bit.. The reason I mentioned seatstay in particular was that when any weld on bicycle frame cracks, that's the one tube that goes through your leg, perhaps piercing your femoral artery.
Holy ...(poop), point taken!!!

FurryOnTheInside said:
I'm not sure this is your biggest concern right now. I don't want to be rude, and I know it doesn't have to be pretty; but to me that bike looks like a deathtrap.
I know!!! That's why I'm replacing it after riding it occasionally for just a few months!:giggle:
So many wierd quirks on this bike, eg. The super-sensitive twist throttle because of a somewhat low twisting travel. And the massive rpm drop between 2nd and 3rd gears, or the 3 second delay in power delivery to the rear wheel at high speeds, that lets the engine rev up, than suddenly the chain goes tight and pulls
Real hard:) And not being able to pull in the clutch while
Moving without the belt coming off(have to stall the motor). Or the ungoverned engine that can blow if over revved. Or the kicking back. Or how it suffers a massive gunshot of a crankcase explosion (that makes my intake and carb come flying off the motor), almost every time it runs out of gas. Or the crazy torque that starts right when the engine is spinning fast enough to not stall. Or the left-side foot brake (bit of a mind gap haha), the list goes on, and gets longer every day. Now you can tell why I only have 45Kms on it! I'm as used to this bike (and my other deathtraps) as I am to my motocross bike, but to anyone else it's, well, a death trap! But I love it, once you get used to it's gypsy-voodoo like ways, it's an amazing bike to ride! I just don't want to break it/myself by riding it too often!:giggle:

FurryOnTheInside said:
Your new bike is going to be awesome though, I'm sure.. with a different motor and an adult bicycle frame you'll be able to make something far better. :) Now how about some pics of this rotary motor then? :D

image.jpg
 
Wow I am giggling now after reading that.. Must be like a drag bike riding position! :devilish: I didn't realise about the footbrake too! :sick: That is one crazy machine!!

Awesome motor.. thanks for showing me a pic of that. It looks amazing too, once I turn the pic the right way up haha.. and definitely worth getting a really good bicycle to put that li'l beauty in! :)
 
good old sachs KM48.

8PS at 5000rpm i think it was.

a pferder starke is pretty close to a HP at this low number.

not bad considering the size of the carb!

and a very strange intake porting system.

PICT0512 (Large).jpg


yours does look slightly better than mine.

im willing to sell certain parts, as mine will never go past being an ornament, the epitrochoid and rotor are STUFFED.

ie, fans, magneto, shrouds etc.

i actually wanted to make a new rotor for my HSC highschool project, out of alloy. that was a long time ago.

it looked pretty bad when i got it too. that goop is old lithium grease. got it when i was 16.

an idea to change the stock bing carb and seperate fuel pump over to a walbro with external pulse feed (ie, anything off a stihl chainsaw, perhaps)

the odd one or two pop up on ebay occasionally.

i remember 10 years or so ago, someone was selling a whole pallet, still in the boxes.

what annoyed me was when i contacted the australian SACHS dealer, he couldnt quite grasp the fact i had a rotary made by fichtel and sachs.... he kept on babbling on about the non sachs bike engines called rotary... i kept saying, wankel, wankel, wankel, until i got fed up and decided he really was a complete moron.


alternatives!


http://www.barnardmicrosystems.com/L4E_wankel.htm


http://www.nwuav.com/uav-products/uav-rotary-engines.html

http://www.wired.com/gadgetlab/2011/06/tiny-rotary-engines-could-power-gadgets-with-gasoline/
 
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Thanks headsmess, I could really use some parts, especially ignition (was thinking about using the stator from the Motorcycle gearbox, and connecting it To a 4 stroke CDI. (But the trigger coil might be in the wrong spot)
But what would shipping be like, I'm in Canada???
 
Ok, so what Im thinking I'll do is get a cheap BMX, because then I can weld on it (I can weld on tons of reinforcements to every joint, and mounting the motor with clamps might make the force applied by the engine too localized on the frame tubes (I'm probably going to weld a massive sheet of steel to the front triangle and mount my motor to that). Plus any decent BMX (Hoffman, Sunday, haro) I've found costs $150 minimum.
Did find a wethepeople frame for 110, but I can't weld to it :( And I'm really cheap.
I think I can make a cheap weldable frame alot stronger with enough mods.

So my 2 choices- a (probably late nineties, looks like the 1997 model) CM Mach 2. The thing that I don't understand about this bike is the bend in the downtube, close to the headtube. Does it actually serve a purpose, because to me it looks like a place where the frame could
Break, as it has no support on the bend. Also looks like it has weak wheels (low spoke count)
http://toronto.kijiji.ca/c-ViewAdLargeImage?AdId=521607423&Keyword=BMX bikes viper

There's also this bike-
http://toronto.kijiji.ca/c-buy-and-sell-bikes-road-Bike-For-Sale-W0QQAdIdZ528259156
A "BENT (brand) 180". Wheels look strong, but it's just another department store
Bike.

And this bike- an Eaton breakaway, made by supercycle (sold at eaton's). Looks exactly
Like a 1983 model.

http://toronto.kijiji.ca/c-buy-and-...eakaway-BMX-Bike-20-wheels-W0QQAdIdZ529163401
 
10mm rear axle may not be up to the job (opinion).. but the original 10mm axle can perhaps be swapped to a 10mm high quality axle. 14mm would be much stronger of course as they're for mounting stuntpegs.
The thickness of the rear dropouts is important.
Threaded 1" steerers and quill stems are nowhere near as good as a threadless 1&1/8" with a properly clamped on stem.
Are you planning to use the pedals/crank as on a motorised bicycle or are you going for footpegs on the back again, or footpegs mounted through bottom bracket?
1. Has scaryy old welded together stem, on a quill steerer thingy. 10mm rear axle. Reasonable bottom bracket height. Bend in downtube won't matter as you're welding a huge gusset into the frame. Old age indicates thin bendy dropouts. Did they really make them this old fashioned in 1997?
2. Has a solid stem, unfortunately also on a quill steerer thingy so better than 1, but not as good as the wethepeople. Dark photos, but presumably 10mm rear axle. Freestyle geometry though, reasonable bottom bracket height. Has a rear v-brake which is unusual on a non-racing BMX and could be useful or could indicate (likelihood of) thin dropouts. Lack of wear-and-tear on the original seat indicates little use so should be a good runner.
3. Has not much going for it IMO, WAY too old, ancient. Bearings all unsealed, even the bearing races will be worn if not actually rusted. It's fair to assume it's a thin-walled frame with paper-thin dropouts. I'd stay away from this.

My vote goes to ...... wethepeople! ;) :p haha.. okay, my vote goes to #2 the "Bent".
 
Yep, that's the bike I was naturally leaning towards because of the wheels.
Could thin dropouts just have a big thick plate of steel welded over them to make them thicker? I had to do that on my lawnmower bike, because I had the chain jam and the axle pulled out of the dropout, bending the slit where the axle goes really wide
 
48 spoke wheels are not nessesarily any stronger, it's down to the actual quality. Comparable quality wheels would be stronger with more spokes. A lot of riders prefer 36 spokes now as quality is good enough these days that they're strong, and the weight saved is more than the strength lost. So yeah it's hard for me to say that they're stronger.. but when comparing two department store bikes, yeah probably true more often than not.
Ah, that is just what I was afraid of happening to you! You might not have to strengthen the dropouts as they could be fine already, have to see the bike to know. But I would think you'd clamp the bike with the rear up in the air and hacksaw down the welds and remove the whole dropout (drill the last bit on the front I suppose), then insert your new dropout made from thicker plate into that slot that is wider due to your sawing, then reweld and harden. Never tried this myself and I don't fabricate frames, my experience is with bolting mismatched stuff together, finding it doesn't fit, filing and bending and bolting it again lol. And I'm assuming the dropout is welded into a slot in the tubes, but who knows maybe the tubes are welded into a slot in the dropout?
 
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