Current Projects chat and miscellany

that's if I can find it, although, they are very easy to make. the press discs in that one were made from bullet-proof glass (taken from IDB house in Belfast that was demolished years ago, my grandad was head of security and somehow bagsied the ground floor windows) but they could just as effectively, and probably far more easily, be cut from wood. so long as they are at least, say, 10mm thick they will stay parallel to each other.

I made another one using just big washers but that was cack

Good point... Headtube is 318mm so might end up with some wood+hammer tappy tappy action.

Feck me!
I've worked out my ideal headtube to around 11cm. I can see why your going custom geo now.
My bike cad looks more like a big wheeled BMX with drops :S

but they could just as effectively, and probably far more easily, be cut from wood. so long as they are at least, say, 10mm thick they will stay parallel to each other.
I made another one using just big washers but that was cack

I cut two additional smaller wooden discs (fit inside the HS cups) to centre the press the avoid the slipping off centre problem.

thats a good tip too, i just held them in place til there was enough pressure but that was a pain in the arse

Thanks for the info chaps.

how come the frame is so big ? im only 3 inches shorter than you Mr Braker and im comfortable on a much smaller frame.
My point being the frame seems excessively big to the point of being massive. is that a fair appraisal ?

It's big, but not excessive :-)
If my cyclefit data is accurate, then it should fit me perfectly!

Because of my limited fork choice and in order to achieve the desired trail, the headtube angle has to be 73deg. If it were at an angle typical for track frames, the length would be maybe 20mm less. Add to this the fact that my saddle to bar drop is only 60mm, and that equals a fuck-off frame.

Good point... Headtube is 318mm so might end up with some wood+hammer tappy tappy action.

Forks / steerer tube may be a bigger problem than head tube & tools.
I remember the longest steel steerer tube Reynolds / Columbus used to be just 300mm.
I haven't seen any longer modern forks either.
Of course there're plenty 6 m long steel tubes that can be used.
So, you've got to use a custom fork I guess.

I've got that sorted actually.... both Alpha Q and Serotta make an especially stiff OTP carbon fork with 450mm steerer.

Cyclefit do put you in a very upright position IMO.

I've found the key measurement from my Cyclefit were the saddle to BB centre height and Q factor. Everything else I normally fudge myself.

Thanks for the info chaps.

It's big, but not excessive :-)
If my cyclefit data is accurate, then it should fit me perfectly!

Because of my limited fork choice and in order to achieve the desired trail, the headtube angle has to be 73deg. If it were at an angle typical for track frames, the length would be maybe 20mm less. Add to this the fact that my saddle to bar drop is only 60mm, and that equals a fuck-off frame.

Same height as you, but there is no way I'd go for such a long head tube.no-rise stem combo. I know that its a custom frame and your a tall guy but that just looks wrong. Maybe a 5 or 10 deg stem would work better for getting the desired seat to bar drop without limiting your choice of forks so much by having such a long head tube.

Is it the aesthetic that concerns you more than the engineering? Sincere question.

Is it the aesthetic that concerns you more than the engineering? Sincere question.

Well, but wouldn't the wheels* for you have to be bigger than 700c? I mean, will you be able to take as much advantage of your bike as someone smaller on a smaller frame, with 700c wheels?

(*same with crank size)

Is it the aesthetic that concerns you more than the engineering? Sincere question.

Your bike will be fine, and looks great,
I am 6ft 3 and have had some pretty large frames, some think they don't look righ... well i think small frames look silly :)

Don't worry about what people say, i'm sure it will fit perfectly, and thats what counts :)

Agreed. It's teenage headtube envy, that's all.

@nuknow, I do use longer than average cranks (175fixed 180road), but i think changing the wheel size would be more trouble than it's worth!

Is it the aesthetic that concerns you more than the engineering? Sincere question.

No nothing to do with the aesthetics, just don't understand why you would go with ahead tube so long that it limits you to a single set of forks. or custom, when a 5 or 10 deg riser stem would give you the same handle bar position with a for more conventional stem position.

From an engineering point of view geometry of your frame is also far weaker. Without resorting to moment diagrams, the less triangular the main tube structures in your frame are the more flexible it is. The long head tube and low slope top tube put a lot of bending moment through the top and down tubes that would otherwise be compressive loads in another frame. If you are so inclined, try downloading a basic finite element modelling package and mucking around with various configurations, or try some structural/mechanical engineering tech books. The concept of small triangular shapes is used in a lot of MTB frames, GT triple triangle frames and all modern road frames.

Far too technical for me :)
From what you say, would a more agressive toptube slope and a stem similar to that which you mention, result in a stronger and more stable frame? Unfortunately, i am getting this made on the cheap and don't have a frame builder as such to discuss with! Any advice much appreciated.

Far too technical for me :)
From what you say, would a more agressive toptube slope and a stem similar to that which you mention, result in a stronger and more stable frame? Unfortunately, i am getting this made on the cheap and don't have a frame builder as such to discuss with! Any advice much appreciated.

Yeah its annoyingly hard to explain (for me anyway) but long head tube acts like a long leaver pivoting around the two joints. This means that under load instead of compressing the down and top tubes the long head tube will make the loads bend the tubes which is bad. Would suggest trying a shorter seat tube, longer seat post and more angular stem, more agressive (compact geo) top tube will also help. This will have the added benefit of making the rear triangle smaller and improving the stiffness.

Look at things like big cranes and truss bridges and , they are constructed from a heap of small triangles because it is a very strong shape, same basic principle behind bike frames. Good seat posts are strong, the with road geo your weight is spread through all 3 contact points (saddle, peddles and bars) so it makes sense to have a rigid frame made up of small triangles and longish seat post and stem. This is the logic behind most modern road frames and MTB frames.

Thanks for the advice, much obliged.
I'll be giving the design a tweak and a fondle before finalising it.

What size is this please?

60cm largest they do

Thanks for the advice, much obliged.
I'll be giving the design a tweak and a fondle before finalising it.

No worries, if you don't have an expert frame builder to guide you some strangers from the internet will do just fine.

Well worth checking out some bigger bike frames just for reference. I'm riding one of the huge surly cross checks at the moment and love it. 6'6" is at the top end of suggested size for most OTP road frames but you shouldn't have to deviate to far to get a custom frame works fits really well.

http://static.londonfgss.com/memberpics12358-albums924-picture5721.jpg

This is my first fixie and first project.....Sorry its so massive, just had this powder coated and stuckit together in the living room.....
pointers please as I know nothing.....and Yes; i realise it hasn't a chain nor pedals!! White bmx pedals maybe??

stay away from any more white ! what you have is about the right balance, a little bland, but hey it looks fine.

what sort of brand....its a 15 year old rigid saracen mtb....No white pedals duely noted!!

Oh, and I know the wheels are pretty nasty.....but their round, so I'll go with them, the seat post is also chrome, but I've taped it for the pic....black one on order!!

http://static.londonfgss.com/memberpics12358-albums924-picture5721.jpg

Plenty of clearance...

Plenty of clearance...

As I said, its an old rigid mtb frame....managed to squeeze the 700c's on there!!

It ain't pretty, but its my first!!