|Project by wyeth||posted 01-24-2011 04:06 AM||5869 views||6 times favorited||7 comments|
This project uses a fairly complicated series of dovetail , floating tenon and mortise and tenon joints to create a spiral 3 step library ladder which is a prototype made from cheap recycled softwoods that I picked up for a total of $50 at a demolition yard.
The vertical axial member was turned from a 4X4” length of treated pine in 2 pieces as my lathe can not handle a full 6’ length and the top piece was carved to resemble some vaguely animal like head and neck shaped so that the head fitted the left had of the user in an ergonomic manner and the “neck” comfortably curves to accommodate the hand as the user mounts the different levels.
I spent some days on “sketchup” modelling the steps and the correct angle for them to mortise into the axial vertical. The narrow end of each step is extended as a single tenon mortised about halfway into the vertical support and there is also a shaped bracing support set about 1/2 inch into the cylinder and reinforced by a dowel into the cylinder and another dowel up into the step.
The supports for the outer ends of the steps consist of 3 planks that are edge glue joined at slight angles using multiple domino floating tenons and dovetailed to the outer ends of the steps. These vertical supports are also shaped to a smooth curved shape and a part removed to give the “cathedral window”shaped opening.
The two vertical axial cylinder sections were joined using a large peg shaped mortise and tenon with a thin slice of slightly contrasting wood between the ends to give interest and make a feature of the join.
All the other joints apart from the above one had do be glued and fitted and clamped in one exercise as there was no way of inserting the three tenons into the vertical cylinder once the outer dovetails were joined and also the outer supporting members had to be edge joined at the same time as the dovetails were glued.
This was quite an exercise for one unaided woodworker and there were quite a few dry runs before i was willing to take the plunge into the glue bottle.
My intention has been to display this prototype and offer to custom make similar pieces using more exotic timber and fitting the step and support heights to the customer. If hard wood were used the whole piece could be made to look less bulky if desired and I would be able to take more care with the joints and finish.
This prototype would serve as a model for future pieces but there are all kinds of variations that can be adapted to the individual tastes of the purchaser.
This piece took me a month working a few hours most days but I hope I could become more efficient however the price would not me inconsiderable.
The ladder is quite stable and the vertical support gives a lot of control and balance. It can be fitted into a corner when not in use and even used as a set of shelves.
This model needs a ceiling height of at least 9 feet to accommodate my 6’ standing on the top step.
-- David Australia