stronger BMX frame- cheap or expensive?

Yeah I know lol, but I'm really careful too. I AlWAYS have a finger on the brake in case something locks up, I keep the revs down so the flywheel doesn't pull apart or the rod doesn't break. And 90% I keep the speeds under 55 or 60kmh, and make threads like this one to get some better advice to keep things safe::D
 
your work is a deathtrap bro. you should see my bike.

i cant help but agree 100% with this.

im sort of dissappointed that you want to use this engine and then make some hideous contraption to support it. so backwards.

it should be mounted in a work of art... no expense spared!

as mentioned, i have one of these engines. i regret having TOUCHED it when i was young. it was me that destroyed the rotor, knowing no better. if id stuck it in the oven, id have popped the seals out in ten minutes... but no, gorilla grip here wacked it with a hammer. the troid was already chipped, but if id had a bit more sense and patience... it could be a going concern if i was given it, say, five years ago, instead of 15. every time i see or think rotor, im reminded of that little fact. it hurts.

it is fun making these things, i know... but at a certain point i started buying real tools so i could make them better. cus when i think back on some of my early attempts, and some of the engines ive destroyed, i sort of cry a little bit.

a really nice engine, all these hours of work i spent, and a few dollars here and there, and because i rushed some parts, thought more of the riding than the making, i ended up with abortions that just frustrated the $#^ outta me!



dealing with mounts that break, not considering the torque reactions and having chains throw every twenty metres on the return leg of what was an enjoyable ride, having to check all these bird:poop: welds and china steel bolts after each and every run... having solid engine mounts crack and break because the frame flexed, carrying exhausts home tucked under one arm, having to keep one foot jammed up against the fuel tank to stop it falling off... all these things caused by just wanting to finish it and ride, instead of concentratng on the task at hand which is mounting an engine securely.

its a way to learn about things, but it sure ruins a lot of good equipment, and gets depressing!

get a tig welder, get a lathe, and stick to just the cheap POS engines for now. please. that engine is a collectors item! keep it on the shelf for a few more years! if you want an engine on a bike, use ANYTHING but this one!

(lathe, welder, drillpress, bandsaw, benchgrinder...probably the top on the list of needed items for making stuff)

in the meantime, fill the rest of the shelf with books on metalwork ;)

(for your own sake too, cause one day you will look back and wonder...WTF did i do??)

not reading this thread anymore, it depresses me. evokes memories :(

ive seen better workmanship on the side of a dirt road in the phillipines...


i mean that in the most offensive way possible :)
 
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True, that's why Ive been waiting to put this motor on a bike. This would be my 5th MB, all were completely built from scratch, and I've made 2 experimental 2 stroke engines. My lawnmower bike definitely isn't my best workmanship (I made it on a zero dollar budget), these are:giggle:
image.jpg
That red engine made 1/2 the HC emissions that It made stock, and emitted not a single PPM of NOx! (Sorry to brag, but I think that's pretty sick lol)

But I've been planning this build for about 8 months now, and have put tons of research into this engine+setup- getting the right CDI with the right advance
Curve, how to detect detonation (you can't hear it as loud in wankel's), and I bought some mazda RX7 apex seals (really expensive part!!) that I will mill down to spec. And that's just getting into it...

I do agree though, that it would be a waste if I put this motor on a crappy bike. My original plan was to build the frame+ gearbox, and if it doesn't seem up to the job then I'll put that 49cc pocket bike motor I have on it:devilish:
(lathe, welder, drillpress, bandsaw, benchgrinder...probably the top on the list of needed items for making stuff)
I have access to/own every one of those :)

Ive seen better workmanship on the side of a dirt road in the phillipines...

You've gotta admit though, those Filipinos are pretty resourceful people! :laugh4:
 
You should put the Sachs motor in a Brooklyn Machine Works "Pooky", or get them to build a version of the "Race Link" especially for the Sachs motor. ;)
 
lol, phillipines. if, if things had gone differently...id be putting my sachs rotor into my tuktuk!

oooh yes, i got one of....four at the most, road registerable tuktuks in australia :) still has thai on the oil tank :)

can squeeze a daihatsu 600 in it, but im really gunna be struggling to get even a 10A rotor in there.... would sound sick but :)


i hate having to keep within "design standards" :(


im not in canada, obviously. brrr. too cold!

me, though...id be making a snowmobile :) screw the bike frame, just use some 1 inch thin wall tube, draw it out, jig up with timber, go make some noise! old tractor tyres for belts look awesome.


i believe thats what these rotors were predominately used for?


a good CVT and the rotor and weeee! white roosters!

scratch build removes so many limitations.

just allow for swapping the front skis over to wheels for summer?

then again, they steer differently , dont they? i dont know. too cold! brrrr! it was 10c here last night! yuk! i just recall hearing that they tilt instead of steer so much...


when it gets down to strength.... look at a 1300cc moto. big engine, yet the frame can still be pretty minimal. its where and how its put together. triangles are our friends :)


8hp will make pretzels out of anything inadequate.

keep stuffing around and you will learn more than any uni graduate with a computer will understand. meaning better designs.

meh, ill go dig up my parts and see if anythings worth doing more with than chucking... :)
 
Headsmess, I think I can see your chip in the rotor. I think you could stick/TIG weld that up (my mig/flux core SUCKS on cast iron, the weld just seems to float on top of the cast (the weld will be glowing and the the cast all adound it won't), I always have to make
Massive welds for it to be strong). Then grind the weld flat, Then you could either grind in the side seal groove, or just leave it and cut the end of the side seal shorter. (Shouldn't make a big difference in compression, and even if it does it will only be on 1 rotor face, and only at cranking speeds. You need to get it running! It's either a ghetto, but running motor,
or a table ornament. Same thing with mine, either I modify a bunch of parts to fit on the engine and complete it, or it's absolutely worthless. Of course I'm going to choose the 1st option :)
 
NO! the welds leave the signature. small flush smooth weld is steel. large obtuse ripled is aluminum. or use a magnet.

I know, but I needed to know if it was chromoly or hi-tensile (both steel).
But the seller said it makes a "ding", so it's probably chromoly, which I can't weld on :cry:
 
I rea that chromoly isn't usually heat treated, but I still can't weld or braze on it because it needs post weld heat treatment, to relieve the stresses. I wouldn't thrust my life on my own uneducated normalizing techniques :giggle:
 
Ok, I read that chromoly can be welded normally with a O/A torch. So if I got this bike, I would braze it (no worrying about using the right kind of filler metal) with my torch.
Sounds like this bike would be the best, because of the reinforced headtube junction and it probably being a subrosa
 
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