T50 vs Q45 boom stiffness?
- Thread starter Rampa
- Start date
dtseng
Well-Known Member
I think the only weak point in T50 is the movable joint between the chain stay and the BB shell. Only the two sides (i.e., boom and fork) of the front triangle are fixed, the bottom side (the chain stay) is not. If that joint can be locked, then the front triangle would be stiff. In earlier Quest with front fork suspension, the front triangle is even more flexible. For urban riding and touring, flexibility in the frame is highly desirable, so your body won't get hard jabs from uneven road surface.
Last edited:
benphyr
Guru-me-not
@dtseng
Your identification of the joint at the bottom bracket on the T50 (and QX100, Quest, Sofrider, conversion kit) is something I never thought about. Seems like it might be the biggest difference between the triangles.
And some of my thoughts that were triggered:
Smaller effects on flex of the front triangle could be flex of boom. chainstays, fork, length of headset, joint at headset, axle, bottom bracket, and then after that some of the peripherals would also have an effect: crank arms, pedals, etc. but the peripherals are not part of the frame.
There would still be more flex from the handlebar to foot connection between the handlebars-stem-fork extension-clamp-pivot-boom on the T50 than there would be on the handlebars-boom direct connection of the Q45, S40, V20. BUT it would be pretty similar if you are only using the triangle and not using your arms. So, this last paragraph describes main differences between beginner and advanced / skilled rider more than it describes between the two models for a beginner.
Similar efficiencies would be noted between me on a racing DF compared to a trained rider: for me the increased efficiencies of stem/handlebar/frame stiffness of the connections between pedal and hands would have very little impact because I don't know nor am trained on how to use them. The pedal to wheel stiffness and increased efficiency would be much more significant for a beginner / non-racer.
I am not an expert so...
rx7mark
Guru
You can find 38mm OD aluminum tubes with 35mm ID. The harder problem for me is how to mount the handlebar to a 38mm tube. I just finished my Emeljay mod and used a 31.8mm slider tube, because I was able to find a bar mount solution for that size tubing. A 38mm tube would have required me to have a custom part machined, greatly increasing my total cost for the mod. I also could not find anyone interested in doing this kind of prototype machine work. So if you don't have the machining tools, or have a friend who has them, then you might be out of luck. If you find a solution for this let us all know.
Mark
Rampa
Guru
Hi Mark,
The first tube I got off Amazon was so close, but ended up binding. I had to order one from a metal supply place. Hopefully it'll work this time. It'll actually end up with an OD of 38.1. I have some clamps on the way too. Anyway. I'll be able to prototype on my old Sofrider. It has enough 34.9 boom to work, but I'll be clamping the new tube on down closer to the bottom bracket.
The Cannondale stems seem to sometimes be 1 9/16. A little to big. But there are some freeride/downhill 1.5 stems out there. I know Truvativ makes/made one. Finding an affordable one might be tricky.
I also was considering cutting the steerer clamp off of a long stem and gluing/clamping it into the end of the 1.5 inch tube.
The first tube I got off Amazon was so close, but ended up binding. I had to order one from a metal supply place. Hopefully it'll work this time. It'll actually end up with an OD of 38.1. I have some clamps on the way too. Anyway. I'll be able to prototype on my old Sofrider. It has enough 34.9 boom to work, but I'll be clamping the new tube on down closer to the bottom bracket.
The Cannondale stems seem to sometimes be 1 9/16. A little to big. But there are some freeride/downhill 1.5 stems out there. I know Truvativ makes/made one. Finding an affordable one might be tricky.
I also was considering cutting the steerer clamp off of a long stem and gluing/clamping it into the end of the 1.5 inch tube.
billyk
Guru
Yeah, I've thought of this kind of thing myself, but always come up on the inescapable fact that every additional joint introduces flex (including glue). That's the big difference between the Q2 and Q45: three joints between the BB and the handlebars vs one.
I have to question @dtseng above about "flex being desirable for urban riding and touring". My experience on the Q2 (mostly urban in a very hilly city) is that flex makes little difference except when climbing, and then it eats your hard work.
Rampa
Guru
All Cruzbikes use 1 1/8 headsets don't they? So you could totally mix-and-match.
Gluing clamping a long stem in the end of the tube should as stiff as the slider tube junction if done properly. I was going to stiffen that up to by extending the slider tube towards the bottom bracket as far as possible. I think it be will much prettier that way as well, with the clamp hiding down by the crank.
Gluing clamping a long stem in the end of the tube should as stiff as the slider tube junction if done properly. I was going to stiffen that up to by extending the slider tube towards the bottom bracket as far as possible. I think it be will much prettier that way as well, with the clamp hiding down by the crank.
rx7mark
Guru
Yep I think this is your best bet, but you still might have to get the cut stem machined for OD to fit the tube tightly if you are going to use glue, you might also be able to weld the cut stem onto the tube, but both require a fairly tight fit for best strength in the joint.
Mark
