I'd like to add a second top tube to my Boardtracker design, about 150 mm below the regular top tube. Is this possible? How would I do that? Thanks.
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Sat, Dec 17, 2011#1
Adding a second top tube
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There currently isn't a specific option for adding a second top tube. However, there are still lots of tricks you can use with the existing options. As you can see below, I've modified your Boardtracker bike by shifting the actual top tube down along both the seat tube and the top tube. Then I changed the attachment point for the seat stays. Instead of connecting to the seat tube, the seat stays now connect to the head tube. The seat stays are also curved so that they pass over the seat tube at the spot where the top tube used to connect. You can connect to the model info for this design by clicking on the image below.
Thanks Brent. Is it possible to terminate the lower top tube on the down tube? Will try later. Having a bit of trouble getting the app to load at the moment.This is a really amazing resource. I'm looking forward to learning more. Have tou thought about a gallery space for people to upload photos of finished bikes? Would be really cool to see the physical results of some of these designs.
There is currently no formal option to connect the top tube to the down tube. However, you can still fool the system into doing it. In the example below, I've made the top tube connect to the downtube at the same spot that the downtube connects. I've also added two bends to the top tube. The first bend is the large radius curve that stretches almost the entire length of the top tube. The second bend is close to the front of the tube. The radius of this bend is 0mm. The deflection is just enough to push the top tube down to meet up with the down tube at a spot a little further from the end of the down tube. As for a spot to upload photos of finished bikes. That's a great idea. I will see what I can do. In the meantime, if anyone has a blog or photos of their frame building projects uploaded to Flickr or Picasa, they can always add a link to that in the "More info" field associated with their BikeCAD model.
Brilliant Brent. Should be interesting to see how my build (or rather hack--I'm going to start with an ordinary cruiser frame, stretch the top tube, bend the down tube and add the secondary top tube) compares to this rendering.
Is there a way to add another parallel, side-by-side, top tube? Ala Mixte-style bike?
Below is an example of a mixte. I based this model off of another nice one by Libraio. This model actually has the top tube turned off. What now counts as the top tube is actually a second set of seat stays that have been attached to the head tube.