Printable View
I am currently working on my 3rd frame and have a question about the st and cs miter depth for the dropouts. On my second bike i mitered the cs as deep as the paragon dropout tabs. www.paragonmachineworks.com - VerticalDR2045SteelRearDropout70DegreewithEyelets. however the dropout interfered with the chain when in my smallest cassette ring. is there a rule of thumb for how deep the miter should be and how far away the end of the chainstay should be from the axle.
scott
Clearance will be influenced by center line offset, cog size (relative clearance needs), chain stay length and angle.
I'm sure there are some tech specs, but in general I would suggest keeping in mind the parts that need to occupy the space and mentally account for them during the design and fit up.
Scott- Did you have a chain stay end bevel/relief on it's inside? Oh i see that you say the drop out contacted the chain. Did you do a before brazing mock up? The usual way this happens is from having too little axle extension to handle the width of the cassette. So i wonder if you do mean my first assumption. That the CS is contacting the chain. Can you provide a photo? Andy.
Andy,
you are correct, it was the cs that was hitting the chain not the dropout. i mitered the cs so that it went almost all the way to the axle which was too much. i did bevel the cs on the inside a little...but not enough. the problem was that i did not order all the parts for the bike before i finished the frame (i learned my mistake and not i have all the parts). i plan on making the cs shorter this time, i am just wondering is there a minimum miter cut needed so that i have a secure connection between the cs and the dropout...i dont want to go too short
Attachment 68048That minimal dimension varies with the small cog tooth count. Back in the day when 14t was the highest cog the stay end was a bunch away from the axle. now what with 11-12t it's less. It should be easy to measure. But I, as many do, miter back the RH stay's inside further then the outside. So the out side look matches the nondrive side's. But the inside still has clearance for the cog/chain. This can also be needed for the seat stay end if it stands to far to the inside. In this case the chain will kick up as it shifts off the last cog and sometimes contact the SS end.
Here's a shot of what i do to the inside of the RH CS. It also shows the holding of the chain peg before brazing it. Andy.
Thanks Andy,
The picture helps a lot. i was originally concerned that if i did not have enough of the dropout tab inserted into the st and cs that it would not be strong enough....but i am guessing from your picture that you dont need a whole not to make a strong connection.
Scott
Scott- As long as you fill the ends of the stays enough to close up the gaps, flow down the length of the tabs and otherwise do good work you shouldn't have much to worry about. Just remember that millons of bike have far worse workmenship then what you'll do and they still manage to survive. Andy.
Andy,
Do you braze the dropouts onto the ss and cs before you weld or braze the ss and cs onto the main triangle or the other way around. On my first two bikes i connected the ss and cs to the main triangle first but i am thinking that is maybe not the best route in terms of cleaning the flux out of the stays after brazing.
Scott
If you're looking for exact measurements Shimano specify this clearance in their manual:
Attachment 68102
Don't forget that the chain also has to rise up and over the smallest cog to get the second position. Seat stay clearance and angle needs to be spot on as well.
Scott- I have always brazed the drop outs onto the chain stays (and fork blades, I make my own forks) first. It's a lot easier to do the finishing work with the CS to be held in a tube clamp, less noisy too. But the vast majority of my bikes have been lugged. I do see the reason to do the drop outs second (to joining the stays to the shell first) if you're filleting/welding the shell joints AND if you're using tabbed drop outs as the sliding placement within the CS gives you one last chance for alignment. But i don't do it that way on the few filleted frames...
Tristen and Bill make good points, same as i tried to say earlier. I wonder if the Shimano chart allows for chain kick up during the shifting. Andy.