9 posts / 0 new
Last post
Mitering and Making Sure Drawn Dimensions Are Parallel


I am trying to determine the exact tube lengths for the bike I am trying to make. In the picture below I have added some dimensions to the top tube and down tube that are supposed to go from the extreme end of one miter to the extreme end of the miter on the opposite end of the tube. From a visual glance these dimensions seem to be accurate, but I am having a hard time telling if the dimensions are actually parallel to the center line travelling along the length of the tube. I am also wondering why the exact length of tube accounting for miters is already present for the seat tube, but not on down tube and top tube.

Thanks for the help

On further research I found

On further research I found that there is a minimum length feature available for the top and down tubes, which complements the seperate miter to miter dimension available for the down tube.  Iam wondering if a minumum length feature has been created for the chain and seat stays yet.

Oh wait, on further research,

Oh wait, on further research, it seems that the e2 measurement seems to get what I am looking for. Is the e2 measurement also representing the minimum tube length for chain and seat stays?

Minimum tube length

BikeCAD has always been thorough about showing the dimensions of the silhouette of the bike. So the minimum length of the seat tube is one of those dimensions that has always been accounted for. The minimum length of the top tube and down tube must take into account the contours of the mitres which weren't initially factored in. This is why the special minimum tube length dimensions were later added for down tubes and top tubes. They are shown parallel to the centreline of the tube.

Meanwhile, the chain stay dimensions you've shown aren't technically the minimum length as the chain stays will still partially wrap around the BB shell. The minimum length of the chain stays is a possible enhancement for a future update of BikeCAD.

On an unrelated note, I can tell from the sag in the chain in this model that there is an extra link in the chain. For a single speed bike, you'll want to set the extra links to zero as discussed at: bikecad.ca/chain_or_belt_drive.

Minimum tube length for chainstays

I see. I just drew this custom dimenion along the center line of the chainstays. This should be the minimum length right? Also, is their a way to constrain a drawn dimension to be parallel to a particular line or do you just have to stick with eyeballing it?

Thanks for all your help

Thanks for all your help Brent.

Minimum chainstay length

Yes. This should give you the minimum length of the chainstay. There is no way to snap user dimensions to geometric entities, but you can zoom in to get very good accuracy.

just checking

Just to be sure, the chainstay auxillery view shows the chainstays from a perspective where the measured length is exactly equal to the length of tube needed to build the seatstays on the bike. For example, if I got 374 mm chromaly tubes form aircraft spruce of about .5 inch diameter, it should fit as long as all of the other parts are in the same spot as in the bikecad sim right?


Happy fourth by the way. 

Chainstay length in auxiliary view

That is correct.

Log in or register to post comments