Sonntag, 20. Januar 2013

Frame sketch

To make my idea of the planned plywood frame more comprehensible to You,
I have made a sketch.
It's rather crude, but understandable, I hope.
The cantilevering extensions of the middle box will take up the swingarms for the rear wheels.
These are placed off center to the red main beams, to provide maximum rear track and room between the wheels for childs/passengers on the back seat.
The geometry is the same as in the recent test frame.


Sonntag, 13. Januar 2013

Cold Water Test


Today I have made a water test to find out if the casein glue is waterproof.
I put a 6-7 inch long part of the hollow beam in the filled bathtub.
The results are the opposite of encouraging, the glue failed completely after three hours in the water.
The former hard drops of glue excess inside the beam have a consistency like rubber.
All four plywood sides still holds together after I picked it out of the water, but it takes just a little force to separate the pieces.

Although so much water exposure will only happen in very rare cases of daily use, I warn You to use casein glue as adhesive for weather exposed parts like a bicycle frame.
Even the water that will be sprayed from the front wheels in foul weather can result in a frame falling into pieces -> an accident -> injuries or death of the driver
Eventually a layer of GRP on the outside surface will make such a construction nearly waterproof, but then I prefer to use epoxy completely.

Pics of the failed glue joints.
The dark spots are screw holes


Montag, 7. Januar 2013

Hollow plywood beam

The first step on the way to the plywood frame is a test build.
I have build a beam that consists of four longitudinal stringers and 4mm birch plywood.
The beam is 2,4m/8ft long, 15,8cm/6'' high and 5,8cm/2 1/4'' in breadth.
Basically it's an rectangular tube with no bulkheads, You can look inside from one end to the other.
The stringers holds the four plywood sides together.
Two strips above has 20x15mm cross section, the two other 15x15mm.
For assembling I used casein glue and little wood screws.
Weight of the beam is 4128 gram, 1720g/m, 516g/ft

A few hours after construction I have made a load test.
I put the beam with its narrow side onto two wooden strips wich are 2,1m/7ft apart (means span)
Then I put my entire weight (90kg/180 pounds) on it.
The beam bends just 2mm.
Thats amazing, the beam is lighter than the quadratic steel tubes I used for the test frame.
And the steel bends 20mm when I stand on it.

Sonntag, 6. Januar 2013

Introduction of the "Retroadster"

Hi all.

My project is a four wheel tandem in sociable configuration and a lot of capacity.
I want to add a fairing to the frame later to make it look like an early streamliner car.
Main influence are the Velocars, which were build by Charles Mochet between the 30s and 40s of the last century.
I call my pedal car "Retroadster"
Until now I have completed a driveable test vehicle with box steel frame and two independent drivetrains.
A simple rectangular plywood box between the rear wheels acts as a trunk for childs and luggage.
Due to the steel frame the vehicle is way too heavy. 63kgs/126 pounds are too much to climb steep hills with reasonable speed.
But it helps to find the exact measurements for wheelbase, track, seat angle, distance between pedals and seats and so on.
And the steel version is easy to change.
Cut it apart with the angle grinder and weld it together again takes just a few minutes.
basic frame
underway on a sunny autumn day
a rear box for childs and groceries