why im currently hating fourstrokes :)

Discussion in '4-Stroke Engines' started by HeadSmess, Jul 4, 2013.

  1. HeadSmess

    HeadSmess Well-Known Member

    so, a friend of mine relies on a motorised pushy. had one of those huasheng kits with a hoot? box, the cruddy ones, on a frame. internet, 200 dollars, was pretty good, but rough, like they all are.

    blew the conrod. way undergeared. so i lent her my lil HT that shes fallen in love with. meanwhile replaced the HS rod with the one out of my old dead HS. week later, it went as well. her ex hubby did the swap job....


    so, her daughters BF had one in his shed, has bought it round and guess who gets to play with it?

    right. :jester: i get a message saying its revving out, wont idle...simply loosen the cable, lol. some people just arent mechanical :rolleyes:

    so, with some fiddling, i got it going.

    now, this one had the single 3:1 chain redux gearbox. big 55T on the wheel. so first ive found it easier to swap motor over between frames. use her first frame, with a 44t.

    well, whoever set that one up in the first place never cared that the chain hits the stay! so that frames gone bin model :)

    the 44t with 11t sprocket, running that 3:1 primary. nope. slug and wouldnt get up a hill. obviously the hoot runs a bit more redux than 3:1!

    so flipped over to the other wheel with the 55t. better but still horrible. and hits the frame worse than ever :) clutch was slipping, and wasnt the best on the hill, but still did it. goes when its wound out :D

    so. clutch has late engagement, making me think this gearbox and clutch is off those 50cc twostroke pit bikes/pocket rockets. looks suspiciously familiar :detective:

    frames rooted, so i guess shes gunna get one of the suspension frames i got out the back. mount the rack, mount motor, find some weaker clutch springs or stretch them a bit, job done :)



    i love fourstrokes but gee i hate setting them up. every kit ive ever seen is deficient and only just "making do". HT just bolts in. everything else is a frustrating nightmare!

    i hate when idiots have worked on them! 1/4x20 gutter nuts do not fit M6 metric bolts!:dunce: frames need to clear chains! :dunce:sprockets need to be lined up!:dunce: bolts need to be inserted so that the motor can be slid across and adjusted!:dunce: all bolts must be fitted and tightened! :dunce:and except for the high end kits, they are just so badly designed/engineered...


    so ive gotten even more determined to do this...

    50cc4stroke.jpg

    4 stroke, single, 50cc, frame mount. give or take. looking at 40mm square configuration.


    yeah yeah, i havent drawn much on that page... just a basic view of crank and rod. background is obviously my layout for working out crankcase clearance, piston skirt clearance etc. i have to draw out a part, try it in all possible positions, determine clearances for next part, etc. lot of work. while keeping other parts still undesigned in mind. like cams.

    also have to keep manufacturing in mind. some things are impossible or stupid, and some things kill multiple birds with one stone :)

    say, use the camshaft as the output? gets a 2:1 redux :) you could even make "symmetrical" cams with two ex and in lobes 180 apart, and run a 4:1 redux! saves on having another geartrain and bearing set and all that stuff in there for the output... just an idea, see. but possibly worth contemplating.

    that shaft with the webs is around 30mm thick. probably be a bit wider in reality to get a wider bearing surface on the crankpin. things like this do actually need some maths, surface area versus film tension of oil versus load on bearing. +50% safety factor.


    most everything else is just a lot of patience drawing, deleting and redrawing...


    how did people design ANYTHING before puters? :jester:
     

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