31511_1442861986 Posted February 2, 2022 Report Share Posted February 2, 2022 Just found this on the framebuilders forum. What you guys think? Quote Link to comment Share on other sites More sharing options...
Canardweb Posted February 2, 2022 Report Share Posted February 2, 2022 (edited) That's well nice! Not a fan of steel's behaviour for trials though. Edited February 2, 2022 by Canardweb Quote Link to comment Share on other sites More sharing options...
PLIW Posted February 2, 2022 Report Share Posted February 2, 2022 That disc mount won’t last! Fillet brazing is an art. Making it nice and smooth like that isn’t always best. Any more info on it. Quote Link to comment Share on other sites More sharing options...
Topsy Posted February 2, 2022 Report Share Posted February 2, 2022 Part of me thinks that that won't hold up well enough. ..The other part of me kinda wants it. Quote Link to comment Share on other sites More sharing options...
31511_1442861986 Posted February 3, 2022 Author Report Share Posted February 3, 2022 On 2/2/2022 at 4:41 PM, PLIW said: That disc mount won’t last! Fillet brazing is an art. Making it nice and smooth like that isn’t always best. Any more info on it. The builder is called Dave Bohm. Found it on the framebuilders facebook thread. Apparently he wanted a bike to start doing trials with. So he built one himself. Thats all I know. Regarding the smooth fillets the way brazing works is by having a root pass done in which the silicone bronze flow inside of the tube mitter and create a inner fillet. This gives it the strenght, the big outter fillet is pretty much overkill, you would need 2 to 3 times the thickness of the wall tubing in the fillet to make it really sound. From the picture it looks like way much more than that. Id say the tubes buckle way before the weld. I say this from doing test runs on fillet tube. The problem with smooth fillet is actually undercutting the tubing while one smooths it out. That can create problems. Quote Link to comment Share on other sites More sharing options...
PLIW Posted February 3, 2022 Report Share Posted February 3, 2022 3 hours ago, 31511_1442861986 said: The builder is called Dave Bohm. Found it on the framebuilders facebook thread. Apparently he wanted a bike to start doing trials with. So he built one himself. Thats all I know. Regarding the smooth fillets the way brazing works is by having a root pass done in which the silicone bronze flow inside of the tube mitter and create a inner fillet. This gives it the strenght, the big outter fillet is pretty much overkill, you would need 2 to 3 times the thickness of the wall tubing in the fillet to make it really sound. From the picture it looks like way much more than that. Id say the tubes buckle way before the weld. I say this from doing test runs on fillet tube. The problem with smooth fillet is actually undercutting the tubing while one smooths it out. That can create problems. I’m a frame builder by trade dude. I use to work at Argos Racing Cycles in Bristol and also Bike Workshop frame building before going on my own. Fillet brazing is just an art and flare, showing off. A brazed joint is fine. Look at Chris and Leeson for example. The mount is unsupported and has very small surface contact for support. It’ll flex and twist off very quickly. Quote Link to comment Share on other sites More sharing options...
31511_1442861986 Posted February 3, 2022 Author Report Share Posted February 3, 2022 13 minutes ago, PLIW said: I’m a frame builder by trade dude. I use to work at Argos Racing Cycles in Bristol and also Bike Workshop frame building before going on my own. Fillet brazing is just an art and flare, showing off. A brazed joint is fine. Look at Chris and Leeson for example. The mount is unsupported and has very small surface contact for support. It’ll flex and twist off very quickly. Thats cool, good to know you're building frames too. Thought you were giving you opinion on fillets in general and not on that specific part of the build. Quote Link to comment Share on other sites More sharing options...
La Bourde Posted February 10, 2022 Report Share Posted February 10, 2022 (edited) Interesting and weird at the same time. The yoke of the chainstays is just incredible... it seems to be CNC'd. Don't want to know the cost of it (steel is really expensive to machine) Some of the tube shapes is unconventional, I don't think you can order this kind of shapes, so it will be interesting to know how he got those. Also the frame has a direct mount disc brake. This is typically used on gravel and road bikes. Not sure what calipers are available in this standard and how much power or modulation you can expect from them. And I agree about the fork brake mount. Really nice project though and I love the look of it. I owned an Explozif Zon'up. It was a perimetric brazed steel frame. It broke twice! The material of the frame has not the major influence on the frame behavior. The specific modulus from steel, aluminium or titanium is almost the same. That is why the design of the frame is much more important. But one has to take in consideration that huge diameter steel tubes will be very easy to dent (to maintain a good weight you have to reduce the wall thickness ), so it is difficult to build a stiff frame (due to the second moment of area, when the radius of a tube doubles, it gets 16x stiffer) with this material. Now if you compare the chainstays and seatstays of a Crewkerz to the ones of this frame, you can imagine that either this frame shall be pretty heavy to get the same stiffness or it won't be as stiff as a Crewkerz (which has much wider chain- and seatstays) Edited February 10, 2022 by La Bourde Quote Link to comment Share on other sites More sharing options...
Ali C Posted February 10, 2022 Report Share Posted February 10, 2022 That yolk is two cnced halves which you then sandwich together, you can buy them in steel or titanium, they’re really cool! I’m curious about the flat mount brakes, I’d thought about using this style of I got a frame made…it’s way more compact and removes the weak “tabs” a normal caliper has. Only issue is no DH powered brakes have this design however Magura do make an MT6 version and that is a pretty powerful brake so should be a decent option. Quote Link to comment Share on other sites More sharing options...
La Bourde Posted February 10, 2022 Report Share Posted February 10, 2022 1 hour ago, Ali C said: That yolk is two cnced halves which you then sandwich together, you can buy them in steel or titanium, they’re really cool! I’m curious about the flat mount brakes, I’d thought about using this style of I got a frame made…it’s way more compact and removes the weak “tabs” a normal caliper has. Only issue is no DH powered brakes have this design however Magura do make an MT6 version and that is a pretty powerful brake so should be a decent option. Nice! Small concern: I think it makes the frame alignment more difficult due to the length of the weld. On some dirt bikes (YT, Norco, DMR, Eastern), there also a yoke with a similar form. But it is not CNC, it is one piece hydroformed piece of steel that goes to the rear end of the frame! Regarding the brake mount: thx, I did not know that the MT6 was available in direct mount. On one hand, I love when someone tries something different On the other hand, as an engineer, having only one solution available on the market is a bit dangerous -that is why I tried to buy bikes without special solutions/standards. Quote Link to comment Share on other sites More sharing options...
La Bourde Posted October 15 Report Share Posted October 15 The complete bike: https://www.instagram.com/dbohemian/p/ClhVXNtSoDz/ Quote Link to comment Share on other sites More sharing options...
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