Seeing as my buggy still has no rear end I've decided to go straight to finishing a springboard axle.
I wanted to make a composite anti-sway bar for the leading link so it seemed like a good time to dive in and finish that too. While it's curing I started making the stub axles and frame to hold it.
Monday, June 22, 2009
Damp and squishy
The original idea for a rear damper was to build an elastomer torsion suspension unit. The concept consists of two sections of square tubing, one inside the other, with an elastomer filling the corners providing resistance to torsion:
The original prototype worked well with only 30° of preload required for my weight. After several hours of work on the 'production' model I was disappointed to learn that the rubber inserts I used were too soft and getting 60° of travel for preload.
This won't be suitable and I'll have to consider finding an alternative rubber or filling them with urethane in future.
The original prototype worked well with only 30° of preload required for my weight. After several hours of work on the 'production' model I was disappointed to learn that the rubber inserts I used were too soft and getting 60° of travel for preload.
This won't be suitable and I'll have to consider finding an alternative rubber or filling them with urethane in future.
Cast off
Wayne Carkeeks' leading link fork design requires the use of 60 shore hardness elastomer donuts to support two short swingarms holding the front axle. These can be had from Mackay Rubber at about NZ$75 a unit which works out to NZ$150 per fork. I found a source for the 2 part casting urethane with a similar hardness. At around $100 for 1.5kg of urethane I can cast about 10 sets. Leaving me needing some time on the machinery to make some molds.
The first molds were solid blocks of aluminium(square mold on the right) milled out to the dimensions with caps and relief holes for overcast. The elastomers proved just hard enough to demold that this was not suitable though the first set came out very nice. For the next molds I went three part and made 4 in total so I can cast a set at a time. I used blue acrylic tint for the first set as used for colouring epoxy which worked well. Though the second set I used a grey tint provided by the supplier. These did not cure nicely and will need to be redone. I'll stick with acrylic tints I know too.
The first molds were solid blocks of aluminium(square mold on the right) milled out to the dimensions with caps and relief holes for overcast. The elastomers proved just hard enough to demold that this was not suitable though the first set came out very nice. For the next molds I went three part and made 4 in total so I can cast a set at a time. I used blue acrylic tint for the first set as used for colouring epoxy which worked well. Though the second set I used a grey tint provided by the supplier. These did not cure nicely and will need to be redone. I'll stick with acrylic tints I know too.
Saturday, June 6, 2009
Leading link fork... hot off the welders bench
In staying with the through-tube design I decided to mix it up a little. Since I'm casting my own elastomers I don't mind integrating the stubs in my design. Smaller cheaper fasteners and less loose parts.
To give you an idea of size, fork is over 300mm or 1' wide and that is a 20mm bolt and 32mm through tubes. I've made another set of rocker arms for the axle mount. The first set did not finish as nice. I will use them on the race buggy leading link fork.
Next to weld on some bolt tabs for footpegs and stirrups.
To give you an idea of size, fork is over 300mm or 1' wide and that is a 20mm bolt and 32mm through tubes. I've made another set of rocker arms for the axle mount. The first set did not finish as nice. I will use them on the race buggy leading link fork.
Next to weld on some bolt tabs for footpegs and stirrups.
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