Bike frame

[Rolsy]

g'day all im am making my own bike frame and have a designe i really like and think would give you more controll and balance and place less stress on the engine mounts. plus i am looking for some thing a bit more heavy duty than the frame i curently have. lol i dont take it easy on the bike. she has hadled it so far but for how long is the question. in my designe i have a frount support strut that i want to have but i havent seen many if any pit bikes with them. i was just wondering if there was a reason for this. if it isnt a good idea for some reason i cant see why not and like i said i think it will imporve it but i thought id get some expert edvice.
please let me no.
ill post some pics tonight. of my designe ( they will only be rough but ull get the idea) im currently at school lol.

 

[mech_eng_matty]

Hey Man,

I'd be very keen to have a look over your designs. Please post em up ASAP.

Cheers

 

[tubes380]

just make a cradle mount frame as this will reduce nearly all the stress on the engine mounts as you are then transferring the force due to your bidy weight to the frame directly rather than to the frame through the engine

i think the reason pitbikes dont run the front strutt is beacuse it would make the frame really heavy and also there not alot of room in front of then engine

 

[FULL-ON]

sounds cool carn't wait to see some pic's

 

[Rolsy]

hey guys im sorry i have had an issue the the comp and lost alot of my stuff so pissed videos and all so my design's have gone to but i just done a realy quick rough basic one in pait then, to keep you going untill i redo them sorry again.
oh and how do i post a pic?

 

[Rolsy]

http://i175.photobucket.com/albums/w130/rolsy/reallyroughbikeframe.jpg

 

[daniel40]

use photobucket

 

[mad man]

man i think you should just use metalwork time for english.

 

[STICK]

Go and feed the choock's mad man

 

[jayden-pitbikez]

^^^^^^^^^^^^^^lol

 

[mad man]

lol i don't have chooks. dam 40 year old pitbikers

 

[wog<-]

lol ur good at paint...i suk

 

[cass38a]

Im with tubes380. I recon its a wast of time trying to reinvent the wheel. Mod and reinforce your existing frame (or get a new one for $70) would be a much better use of your time. Have a look at what Mack is doing.

 

[pascal125]

just add som mods or as cass said, buy a new frame if ur not happy!
u won't pay over $100, what is the problem with ur frame now, startin 2 bend?

 

[mech_eng_matty]

Im with tubes380. I recon its a wast of time trying to reinvent the wheel. Mod and reinforce your existing frame (or get a new one for $70) would be a much better use of your time. Have a look at what Mack is doing.

Rolsy,

Don't listen to the guys that tell u to just buy a new frame, if you really do want to design and build one yourself then i say go nuts man. New inventions don't come about by people just buying whats already out there, people are always changing stuff in an attempt to make it better, thats what modding is all about.

It is not going to be an easy job though; its not as easy as slapping a few bits of steel together and welding it up in the shape you want.

Bike chassis are designed to have a certain degree of flex in them to aid the handling characteristics of the bike. MotoGP bikes can actually stiffen or soften their chassis to a certain degree as another form of adjustment.
Now, most mini bikes aren't exactly a Honda RCV1000 so i can't say for a fact that their chassis are "designed" to have this same function. Of course the chassis is going to flex but that may just be due to poor design rather than an actual characteristic of the bike.

I say go right ahead and design one yourself, get an engineer to look over it for you (if you cant find anyone else then i'll attempt to have a look myself), talk to some fabricators about how your going to manufacture it etc etc. Its going to be a costly experiment though, if your using chromolly which needs to be TIG welded for a good finish, your looking upwards of $40 per hour on labor, chromo is not cheap to buy, maybe $100 per meter depending on size plus getting it bent into the right shape is going to be a bitch coz of how brittle chromo is. You coud of course use steel which is cheap and strong but also heavy as a freight train. The last thing is something that was pointed out earlier, there is not much room at the front of a mini, your chassis rails would simply have to cradle the bore of the engine coz i don't believe there is any engine mounts on the head. Its gonna be tricky, but doable, perhaps a removable sub frame would work so u can still take the engine out sideways?

Weigh up how serious you are about the whole thing, if you've got time and money to burn then do it bro. It'd be sick to see a new kind of evolutionary chassis.

Good luck

 

[Cactus Jack]

About all you could do is make a pitbike type frame with SL70 type front twin cradles - the engine could be easily removed from them ! I think that's what he had in mind ! Most horizontal engines will bolt straight into them !


http://i18.ebayimg.com/03/i/000/99/a4/b85c_3.JPG

http://i9.ebayimg.com/07/i/000/99/a4/b744_3.JPG

http://i11.ebayimg.com/04/i/000/99/3f/7a2e_3.JPG

http://i18.ebayimg.com/01/i/000/99/3f/7c3c_3.JPG


SL70's were the go before the XR75's were released in 1973 and the vertical XR engine design anhilated the horizontal motors of the same cc due to far superior airflow and a far more advanced valve train . Horizontal engine valve springs are a laughable joke and toy-like junk in comparison to the stock XR springs - the XR's were super reliable and could be revved to over 12,000 rpm for years without valve or spring problems .

 

[Rolsy]

thanks all for the positive feedback sorry i havent been on since my last post ill add the pic i did today at school of the design for you

 

[Rolsy]

bikeframe.jpg - Image - Photobucket - Video and Image Hosting
there is the better designe guys let me no what ya think

 

[Trashthumpy]

i see a problem though, the bottom bar (that istn usaly their) would have to come out alot more that that, because of the long horizontal engine.....

 

[mech_eng_matty]

i see a problem though, the bottom bar (that istn usaly their) would have to come out alot more that that, because of the long horizontal engine.....

You could get over that by creating a Y shape at the botom of that link so the head/rocker cover actually pokes through gap in the Y.

The problem with that is:
The whole idea of putting the extra link in there is to strengthen the chassis on landing jumps or hitting bumps. When that happens without that link in there is that the chassis will have a tendancy to bend upwards. The new link will therefore be under tension upon landing a jump (in otherwords, the link will be trying to pull apart, just like a bit of clay/playdough when u pull either end of it). This tension will pull the underside/cradle area upwards with it and could cause problems getting the engine out etc etc. On the otherhand, if the link is in compression (trying to squash it into a smaller size), the Y member is nowhere near as strong as a single member.

Long and the short of it, i rekon it can be done however i might be inclined to manufacture the bottom link and try it out on the chassis you've got to see if it makes any difference before you make a full chassis.