Tandem bicycles

I feel bad that I told some people at last years NAHBS show that I hoped to have a tandem version done by this year's NAHBS. Well, it's the eve of NAHBS 2012 and I've been too busy with other tasks to start work on the tandem option. All I'll say for now is that it's definitely moving up in the queue.

Please, bring the tandem option on bikeCAD!
:-)

Another "yes please"... *goes back to twiddling thumbs*

I'm another person who is looking forward to this.

I'm going to bump this thread and say I have been playing with the old TandemCAD and the Pro 10.0 version and I can get different numbers out of the 'same' model.

If I select BB drop, HTA, fork, etc to all be the same I get different mitre - mitre lengths for the tubes. Not much, but still a mm or 2...

If you are using the old TandemCAD, then you are modeling a tandem. If you are using version 10 of BikeCAD, then you are modeling a single diamond frame bike. So they are obviously not going to be the same model. However, I trust what you have done is modeled the front end of the tandem and done your best to match up the specs on that with the front end of your single bike. You claim that you have chosen the same BB drop, head angle and fork. If you are seeing a discrepancy in miter lengths, my assumption is that you have still failed to match at least one critical dimension beyond the few dimensions you've already checked. Remember, all the following numbers would also have to match if you want the down tube to be the same on both models: front center, BB shell diameter, lower stack height, fork length and rake, down tube and head tube diameters, extension of head tube below bottom edge of down tube, down tube offset at BB.

I'm pleased to report that it is now an option to model a tandem bicycle in BikeCAD version 11.

I have to say this is a great upgrade!

Hi Brent, thanks so much for the Tandem option in version11 !! I can't wait to give it a workout. I've just sent out a quote on a tandem and was pleased to be able to add my first draft tandem BikeCAD design with it.

It was great to have crossed paths with you in Australia all those years ago. You're a good bloke!

Thanks for the kind words everyone.

Ewen, working with you in Australia is where the seed got planted for BikeCAD. I have fond memories of that time and am still proud to say that I once rode on the back of a mountain tandem piloted by an Australian downhill champion.

A couple of things I'd like added nw the tandem feature is here:

UCI rules section updated so front BB is used for bar position checking
Gap between top and down tube be able to give gap between top and extra tube, and extra tube and down tube

Not a tandem feature specifically, but a way to make the rider 'fatter' or skinnier, or other limb sizes to look at thigh/gut interferance issues

Thanks for the feedback. I will investigate all that in a future update.

As for changing the fatness or skinniness of the rider, you can already do that. In the Rider anatomy tab, changing AD, KD, ED and PD will all change the appearance of the rider.

When designing a tandem, or a bike with extra tubes, they don't display a line on the intersection in the main window, nor do mitre templates get printed for them. Can this feature please be added?

Also, when using really big tubes (44mm TT and 25.4mm SS), the TT and SS templates overlap. I can always print a 2nd copy of the page, but just thought I'd let you know. Can't imagine it will affect many builds.

I assume when you speak of a line of intersection on a tandem, you are referring to the joint highlighted below.

Notice that if you run a single tube from the head tube to the boom tube, there will be no intersection shown. However, if you model this arrangement using two extra tubes instead of one, you will get an intersection as shown in the second frame. BikeCAD will also give you the miter to miter lengths for these tubes. I understand that what I'm showing as two tubes often is a single continuous length of tube. I agree that it would be nice to model it as such and will try to make that happen in a future update.

Thanks also for the note about miter templates. I will try to get the extra tubes accounted for in the miter templates. As for large tubes overlapping on the templates, your suggestion to print a second sheet is a good idea. The templates will also be more spread out if you choose an 11"x17" sheet instead of an 8.5"x11".

I had modelled it as a single tube.

I was also looking at the lack of displayed intersection of rear ST, boom tube, and extra tube. The extra tube displayed an intersection with the boom tube, but not the rear seat tube.

Thanks

You have a good eye. I will look to add miter contours to the boom tube in a future update.

Currently, BikeCAD calculates the miter to miter lengths for an extra tube based on the two tubes that the extra tube connects. If the extra tube happens to attach at a corner and therefore intersects more than one tube at one end, the miter to miter dimensions will still just assume that the extra tube fully connects to the tube specified in the Extra tube dialog box.

Presenting more options for complex intersections is something I will try to account for in the future.

Another comment regarding the tandem model.

The boom tube does not seem to have any mitre-mitre lengths assosiated with it

Great to see the update to 11.5 now prints the mitre templates for the extra tubes of a tandem, however the boom tube does not realise it is (possibly) intersecting with the seat tubes, yet.