NVWOCI WVS Posted April 25, 2007 Report Share Posted April 25, 2007 (edited) so basically, i want to design and buil a new trials frame for my a level tech final project! i want a horizontal dropout stock frame and i made a cad model on prodesktop with my initial ideas...the models arent finished, its going to have a steel plate across the back between the seatstays to stiffen it up and act as a brake booster/something to sit on! i plan on mounting a magura on the underside of the seatstays as the frame will be really stiff there anyway and i will use a booster with it too! i reckon this will give the bike really good lines?!anyway, this is only my initial idea and any suggestions for improvements would be very welcome!thanks, heres my cad model...edit:the frame will be made from fillet brazed reynolds 853 steel hopefully!ok, so heres the second draft of the frame(after losing 2 hours work and finally finishing it at 01:10AM!), some slight tweaking, specicfically to the bottom bracket/chainstay area, plus the booster plate has been added, and this time the geometry is as follows:*72deg head angle*385mm chainstays* 1070 wheelbasepretty standard geometry wise really! anyway...what do you think of this one?... Edited April 25, 2007 by samdoman Quote Link to comment Share on other sites More sharing options...
Ryan. Posted April 25, 2007 Report Share Posted April 25, 2007 looks really good mate i was looking at doing this for my a level next year but am put off a bit as i get the feeling its going to take ages to finish!is it that hard?? and what tech have you choosen?? Quote Link to comment Share on other sites More sharing options...
James Quigley Posted April 25, 2007 Report Share Posted April 25, 2007 A friend of mine made a frame for his A level tech.Only he cut up about 4 different frames, welded together a contraption and put an electric motor in it. Put body panels on it and the lot, looked sweet, will try and get pictures.Not a useful post but I'm bored - oh and good luck with it. Quote Link to comment Share on other sites More sharing options...
Bill_B Posted April 25, 2007 Report Share Posted April 25, 2007 (edited) I can't help thinking your seat tubes should be angled back a little more the whole area between the top tube and seatstays somehow looks weak, it may be fine with the steel plate brazed in or even just as it is, I would personally try and go for more triangulation as it makes things very strong. the twin seat tubes look cool for sure but I think a single traditional seat tube type affair would be stronger and maybe take the seatstays right up to the top tube brazing them to both the top tube and seat post. Or even take the seat stays to the top tube and just bring your seat tubes up to join the stays as you have there but less abrupt bends near where the stays join the top tube, I imagine their is a lot of stress in that area. You can then use the fact the seat stays are brazed onto the top tube as a way of running the cables (rear brake and gears but I assume this is going to be single speed, but the dropouts look quite wide apart) inside the tubes, makes for a really tidy looking frame.Please bear in mind what I have said is based purely on how it 'looks' I havn't tried any real analysis of your design.I like it though Edited April 25, 2007 by Bill_B Quote Link to comment Share on other sites More sharing options...
poopipe Posted April 25, 2007 Report Share Posted April 25, 2007 I think a shallower angle on the chainstay/BBshell join would be stiffer too - so the stays are attached nearer the edges. you've got plenty of spaceI'm no expert so get a 2nd opinion Quote Link to comment Share on other sites More sharing options...
Bill_B Posted April 25, 2007 Report Share Posted April 25, 2007 Also I don't think you can get 853 in small enough diameter for chainstays etc so you may have to use 4130 or another type of Reynolds. Have you considered using box section for the rear stays, IMHO it looks quite cool and you would get nice big area to braze to the BB, it would also be very stiff for your brakes. Quote Link to comment Share on other sites More sharing options...
NVWOCI WVS Posted April 25, 2007 Author Report Share Posted April 25, 2007 yeah, absolutely agree with all you've said! as for the box section chainstays thats what i was thinking too as an option, so thanks!i've just been in contact with reynolds and they recomend that i get hold of some plain guage 4130 tubing which apparently brazes really well!and i reckon 4130 will make the bike feel really nice as it's weight to strength ration is really good and iu love the feel of cromo bmx frames which are really solid bot not overly-stiff if you know what i mean?!?any other suggestions?geometry-wise, i really love the way my echo pure rides with pashley forks, so i'm probably going to go for a similar geometry to that i reckon!thanks Quote Link to comment Share on other sites More sharing options...
future orange 660 Posted April 25, 2007 Report Share Posted April 25, 2007 hmmm. do you have to build it? or is that just something extra? because we only had to design. if you have to build thats a shame because to be honest..its going to be quite heavy and poor welds etc and does not give you time to add complex features wheras if you design a frame that isnt designed to be easy to make... could get something good. plus if its steel im sure many experienced frame builders would build for a price.4130 though? rather u ride it than me. Quote Link to comment Share on other sites More sharing options...
NVWOCI WVS Posted April 25, 2007 Author Report Share Posted April 25, 2007 hmmm. do you have to build it? or is that just something extra? because we only had to design. if you have to build thats a shame because to be honest..its going to be quite heavy and poor welds etc and does not give you time to add complex features wheras if you design a frame that isnt designed to be easy to make... could get something good. plus if its steel im sure many experienced frame builders would build for a price.4130 though? rather u ride it than me.yep, designing and building as next years A2 project...i can fillet braze it well enough myself, thats the same construction technique iolo uses so it should be fine! Quote Link to comment Share on other sites More sharing options...
Joe_Elding Posted April 25, 2007 Report Share Posted April 25, 2007 Might just be the angles of the pictures but it looks like you would have to have a reallly long bottom bracket to not hit your feet on the seat stays. Quote Link to comment Share on other sites More sharing options...
NVWOCI WVS Posted April 25, 2007 Author Report Share Posted April 25, 2007 Might just be the angles of the pictures but it looks like you would have to have a reallly long bottom bracket to not hit your feet on the seat stays.yeah, i didnt realise that until i'd finished the model, but the next version will have shallower angles where the chainstay meets the bb to give enough clearence...thanks for noticing that though. Quote Link to comment Share on other sites More sharing options...
Walleee Posted April 25, 2007 Report Share Posted April 25, 2007 Have you a jig for making it? that would be a suitable project in itself.are school actually going to get you 4130 from reynolds? your lucky if they are, order more than you need so you can make modifications down the line.I hope you very good at brazing because soe of the join's you've made there will need to be perfect for a braze to have any considerable strength, i'd be filling them all up with big fat welds, and then smoothing them off, but that takes more time, which I guess is at a premium.... Quote Link to comment Share on other sites More sharing options...
RR_Trials Posted April 25, 2007 Report Share Posted April 25, 2007 I took graphics for GSCE and there were'nt enough people thast wanted to do it so it was murged with resistand materials and is now called product design.We have a free range we can either just deisgn on the computers or just make or do both. We can use any material within reason and the school will get it for us.I might make a frame for year 11. Quote Link to comment Share on other sites More sharing options...
NVWOCI WVS Posted April 25, 2007 Author Report Share Posted April 25, 2007 Have you a jig for making it? that would be a suitable project in itself.are school actually going to get you 4130 from reynolds? your lucky if they are, order more than you need so you can make modifications down the line.I hope you very good at brazing because soe of the join's you've made there will need to be perfect for a braze to have any considerable strength, i'd be filling them all up with big fat welds, and then smoothing them off, but that takes more time, which I guess is at a premium....i can get hold of a suitable jig from work (a bike shop!)i reckon the school will pay the most of it but i dont mind chipping in if i get a frame out of it at the end and i hope my brazes are good enough, i'm going to spend ages getting the tube profiles perfect before i braze them, but i'm going to spend ages practising my brazing before i go to the frame! yeah, brazing isnt too hard anyway really! Quote Link to comment Share on other sites More sharing options...
Walleee Posted April 25, 2007 Report Share Posted April 25, 2007 yeh it's easy, but it's the preparation that matters. you seem to know that anyway Quote Link to comment Share on other sites More sharing options...
Broomer Posted April 25, 2007 Report Share Posted April 25, 2007 Got enough tyre clearance there lol. Should be nice when its done, saw a home made frame thing here a little while back which looked kind of crazy, made out of box section if i remember correctly. Quote Link to comment Share on other sites More sharing options...
Ash-Kennard Posted April 25, 2007 Report Share Posted April 25, 2007 sick, any geo decided yet? Quote Link to comment Share on other sites More sharing options...
NVWOCI WVS Posted April 25, 2007 Author Report Share Posted April 25, 2007 (edited) sick, any geo decided yet?yep, well, i like my '04 echo pure and how it feels...but i can see room for improvement so this is what i've come up withprovisionally...*72degree head angle *1070 wheelbase(but not exactly...horizontal dropouts), *+10mm bb rise*365mm chainstaywhat do you reckon?any suggestions on geometry?im gonna do 2nd version of the frame on cad tonight, i'll post it up here later!cheers Edited April 25, 2007 by samdoman Quote Link to comment Share on other sites More sharing options...
manuel Posted April 25, 2007 Report Share Posted April 25, 2007 (edited) 385 stays = winplus i think you will struggle to make 365 out of steel - as youll probably end up with no tyre clearance. - with ally you can use fancy cnc bits to overcome these sorts of problems .. Edited April 25, 2007 by manuel Quote Link to comment Share on other sites More sharing options...
Orgun_Donor Posted April 25, 2007 Report Share Posted April 25, 2007 +20 BB Its nice for manuals and bunny hops still while giving it a trialsy ish feel.Id also say 375mm stays Quote Link to comment Share on other sites More sharing options...
NVWOCI WVS Posted April 25, 2007 Author Report Share Posted April 25, 2007 385 stays = winplus i think you will struggle to make 365 out of steel - as youll probably end up with no tyre clearance. - with ally you can use fancy cnc bits to overcome these sorts of problems ..yeah, i quite like an uber short back end but tyre clearence is an issue, hence the ridiculous angle where the chainstays meet the bb in the model!!anyway, cheers guys Quote Link to comment Share on other sites More sharing options...
NVWOCI WVS Posted April 25, 2007 Author Report Share Posted April 25, 2007 biggest gay ever i just started making a new improved cad model with more accurate geometry and stuff, really precise...just finished the rear end, the bb, chainstays dropouts and seatstays, they loked so much better than the old ones too!my computer just crashed and i lost the lot :( about an hours work!o well...gonna start again now! Quote Link to comment Share on other sites More sharing options...
Bill_B Posted April 26, 2007 Report Share Posted April 26, 2007 (edited) Come on then, where is it????I've been trying to think of something innovative you could do with this, instead of 'just' designing and building your own frame, is there anything you can do that no one else has to make it a truly better and NEW frame design. I'm sure you will do VERY well in the project if you can show some real ingenuity with the design.So my contribution, in order to make the rear end as short as possible, have you thought about trying to design it with an integrated bottom bracket? a bottom bracket only needs to be fat atthe ends where the bearings are, the middle is just a tube for the axle to run through. How about instead of a bottom bracket 'shell' for the BB to fit into, you make the BB shell into the outer of the actual bottom bracket. you may have to design your own BB with sealed bearings etc, but I think it could easily lose you a good few mm off the back of the bike allowing you to shorten the rear end. Providing you design it with replaceable bearings it should be fine and IMHO an innovation. you can still fatten it out around the bearing area to accept good big bearings and give plenty of surface for the chainstays to be brazed onto. but it can all be slimmed down in the middle of the axle to get the tyre right upto the BB. the bottom bracket would need to be turned up on a lathe to get the right shape etc but I think its all feasable.good idea or bad idea??EDIT: just seen you have edited your first post with new pics,I like it BUT, I would try a single 'seat tube' from the BB up to the top tube before it splits to the seat stays, keep your two 'seatpost' pieces you have now but bring them down at a more horizontal angle to meet the new seat post not the BB. I think this would be stronger without adding much weight and give you a little more clearance for the rear wheel.EDITTED EDIT: what type of brakes are you intending to use, Disc, Rim, Vee? and what size wheels will it have? Edited April 26, 2007 by Bill_B Quote Link to comment Share on other sites More sharing options...
chrishayton Posted April 26, 2007 Report Share Posted April 26, 2007 365 backend will be awful, 375 minimum, 380 is perfect and 385 aint bad Quote Link to comment Share on other sites More sharing options...
Walleee Posted April 26, 2007 Report Share Posted April 26, 2007 why does the downtube come out the arse end of the BB shell?That just decreases clearance and add's weight why can't you weld the stay's directly to the bbshell? Quote Link to comment Share on other sites More sharing options...
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