OK, it's been a couple of weeks...
Samples arrived this afternoon and were assembled (after a bit of tolerance management with a file) and overall I am very happy with the prototype. They have proven that the concept is good and also helps me to understand where more work needs to be done.
Some time in the next 3 weeks I will order a small production run of the new version. The video
here shows the sample that arrived this afternoon. There are a couple of images which show the sample alongside the original and the second sample in a deconstructed state.
Below that I'll talk about the next batch and what I've decided to change and why...
The protoyypes tell me that everything can be made to fit and that the operation of the button and its interactions with the handle is sound. After the last round of discussions I decided to go wholesale on the rectangular version of the button. I also developed my thoughts on how to allow the Z3 key (or a screw driver) to be used to prevent inadvertent pushing of the button.
Having designed the model of the original 507 / 700 handle and looked at the desired positioning of the handle on the door I concluded that it just wouldn't work. There is no practical way to move the lever on the door latch by pressing a button when the lever wants to come towards the outside of the door, i.e. in the opposite direction. BMW get around it on the Z3 by having a handle which when pulled up pivots around a point and operates a lever which then pulls the door latch lever. That'll be quite a different action than what the 507 handle was designed to do.
The desired position of the 507 handle (on or just above the swage line) places it at the same position as the door lock lever which is rather inconvenient for the original 507 / 700 handle but rather nicely convenient for the new version (below). The new version borrows some of the techniques from the Grassbank
Classic Italian style handle.
To operate the Italian Job I developed a cable guide which effectively replaces a pulley which is often used to invert the action of the push button (a push) into the pull action which the lever needs. I had to create a new cable guide for this handle and was able to integrate the push lever directly into the handle as you can see in the images.
The cable guide is fixed to the inside of the end of the door panel with an M6 bolt and a nyloc. I have a jig which precicely locates it where it needs to be. With the Italian handles I also produced a mounting template for the handle and I'll do the same for these. As with the Italian handles a loop of stainless steel cable will be crimped onto the Z3 latch lever, that's the tricky bit. The cable will be threaded through the cable guide which will present it to the lever of the 507 handle. I have created a threaded end and a hole through the thread. A nyloc threaded on to this will allow for adjustment before fully clamping the cable in place. This should be a lot easier to install than our Italian handles which are tucked up high on the top of the door.
It will be necessary to cut a bit of an opening in the Z3 door panel to gain access to the 507 handle for fixing purposes. The door skin fibreglass is around 5mm thick. The front of the handle has an M6 thread onto which a washer and a nyloc can be fitted. At the rear there is an M6 thread and something like an M6 x 8mm bolt (with a bit of loctite should secure that end. I think I will also offer a spreader which you can bond onto the inside of the fibreglass and onto which the M6 bolt can fasten, just to save the fibreglass from too much strees. Having said that 5mm is a lot of fibreglass.
The Z3 lever has around 25mm of travel and the latch is released around half way. If you have read my understanding of the dealock issue in our
reference library you will understand why we advocate a cable solution rather than a lever approach which usually includes driving the original Z3 door handle...
As a cyclist I have a high level of confidence in the reliability of cables when it comes to critically important issues such as stopping my mass and that of my bike when travelling down hill at speed. They also work quite well on Z3 handbrakes... The real benefit in this case is that the lever has 27mm of travel so you can build in more than a couple of millimeters of slack which will ensure that the Z3 lever is back where it needs to be without impacting the operation of the system.
One key point relates to the half cocked position of the handle. The spring which is built in to the Z3 lock system is quite strong. I am concerned that when the handle comes out to its half way position it might get pulled closed again by that spring. Not knowing what BMW did on the inside of their original 507 locks I can say how much force was applied in the half cocked position. The original solution allows for the handle to be put in the half cocked position and then pushed close again. I don't think we will be able to do that so I propose that when the handle get to the half cocked position it becomes latched there and will not be able to be pushed closed. Instead you will have to pull the handle fully open to release the latch and so allow the handle to be returned under the force of the Z3 lock lever spring.
Finally (apart from the cosmetics which need a bit of a revision to get the shape of the top of the handle closer to the original) I have developed what I think is an elegant and will be a cost effective mechanism for preventing the push button from being pressed. You might also notice that the push button side of the handle is much slimmer. That's because all the push button is doing is moving the handle into the half cocked position which also starts the action on moving the lever, after that the handle does the rest of the work by continuing to pull the cable through the cable guide and so drawing the lever outward and downward.
I'm due a couple of weeks holiday starting on Monday so I'll catch up with you towards the end of the month, by which time I hope to have those production models on order...