bicycle bits

[porter_jamie]

this is a link i made for a friends full suspension mountain bike.The idea is the longer link lowers the rear and makes the headangle slacker, which is supposed to make the bike more stable when you are throwing yourself off the side of a french alp! the dimensions were modelled off a link you used to be able to buy from the frame maker called an 'alplink'





i rode it afterwards, and i think it made the steering feel more stable, but i probably imagined it!

 

[porter_jamie]

this is an engine rocker i made for my brothers race bike. the idea was we needed bigger inlet valves, but the ones we had were almost touching because they we as big as we could fit anyway. so, we moved them apart some, and fitted even bigger ones. this took quite a bit of jiggery pokery, as you can imagine, and needed a new rocker with wider finger spacing.





we pulled the old seats and guides and welded the old head up, and refitted bigger seats. we decided to offset bore and oversize the guide parent bores and make oversize (not eccentric) new guides, which you can just see. it did work, and we got an extra 7 bhp on the local dyno, which we were very happy about. to be honest, it's not a very good job, it leaks oil out of the welds, and in a couple of places we broke through the cast material, and we had to patch it up with liquid metal and so on. but as proof of concept, it's a winner. there was some talk of a billet one, but i think thats some time away yet!

 

[Tom Griffin]

Nice job on the rockers. It looks like it was a fun project.

What alloy did you use? Hopefully you polished out all the stress points!

I used to rebuild heads for a guy who raced Kawasaki drag bikes. He would spend a ton of money on flow work in the heads and then blow up the engine. My job was to weld the pieces back together and re-machine them. That often meant reconstruction of the lifter bores and cam bearings, which was quite a challenge.

Tom

 

[jumps4]

you do some nice work jamie
steve

 

[porter_jamie]

cheers chaps.

the rocker was made out of EN24T, which is think is about the same as 4130. It seems we can only buy it in round bar, so we hacked a lump off some 8" bar my father had, and sliced it up so the grain was going along the rocker, not across.

we gave it a good polish and it has managed hours on the dyno managed a whole season racing and has not broken yet. I fully expected it to smash its way out of the cylinderhead the first time we fired it up....

 

[09kevin]

Nice work Jamie! What type of racing does your brother do?

Kevin

 

[porter_jamie]

it is a class called supermono, the rules are: 1 cylinder, fourstroke. and thats about it really. no turbos etc.

unfortunately this class does not exist any more in the uk, but there is a really good class in europe. we have not been racing for a couple of year, babies and things get in the way!

the engine is based on a rotax 604, with billet crankcases (that was a job and a half), our big valve head, we even tried fuel injection for a while, but it was too much hard work trying to keep it reliable, so we went back to carb. we made the frame, swingarm, exhausts, tank, and most of the other bits. (well, my brother did really)

 

[AirChunk]

Awesome Job Jamie!!!

 

[porter_jamie]

a later iteration


final spec it made 72rwbhp on a dynojet, and weighed about 110kg

 

[porter_jamie]

balance bike


billet wheels!