A little project I have been working on recently is a custom sprocket cover for my 919.
It started as a few pieces of MDF to form the pattern and I had the pattern sand cast in alloy (old school). This is my first experiment with this method and I had a chat to the casting guy to understand the process so the pattern I made would work. It came out pretty well with only a little change I'd make to the front piece to get a cleaner extraction if I was to do more casts.
The first images are the wood pattern shot with a coat of primer before being cast. The rest are the cleaned up finished alloy product. I had a can of spray paint mixed up to (in theory) be close to the titanium colour of the engine but it turned out I was a shade or two too deep and grey. It is expensive to order paint in this manner so it may stay this shade for a while!
Cheers guys. The pour is aluminum. I comes out looking a bit etched as expected from a sand cast but can be easily cleaned up with a 120grit sanding flapper. You could polish it up if you desired.
My original design is as completed but while fiddling around it is a 3-in-one option - you can run just the back cover so the sprocket is more exposed, with a couple of spacers you can run just the outer cover (mind you there is no engine protection if a chain breaks like that) or as intended in the photos.
Darn - I may need a prettier front sprocket now - that stock one is very plain!
I find it good fun making stuff like this - there are a couple more ideas floating around for the bike yet .....
"Security is mostly a superstition, it does not exist in nature: avoiding danger in the long run is no safer than outright being exposed. Life is either a daring adventure or nothing."-Helen Keller
Location: Santa Maria, CA Otherwise known as heaven on earth.
Posts: 1,797
Excellent work! And modular to boot.
Did the foundry cast both pieces in one mold or separately? I ask because I have been doing nonferrous sand and investment casting since I was 10 years old, and there is no feeling quite like taking a design fron an imagined concept to finished parts by yourself. See a gyro housing I made for a steadycam project below. The pattern was generated stereolithographically from a CAD design about 6 years ago and used for the pattern for sand casting. The one in the picture is an unfinished extra.
Infinitely adjustable, made of the finest materials available, and completely sourced from local suppliers -- gotta support the local economy! Order today and know handlebar Nirvana.
Looks great! But whats the bungee cord in the 4th picture for?
Well spotted! After all the major earthquakes we have had here over the past year when the bike is parked up in the shed I place a brick front and rear of the back wheel, strap the bars to the rafters and bungee the sidestand down so if it jumps forward enough it will not retract. So many bikes were thrown over due to the force of the shakes
This method saved my bike in February's ripper.
Rob, I'm not sure if he used one mold for both pieces - he was planning on doing it that way. Once I was happy with it he said there are options to reduce costs on mulit- casts. I may have a chat to see what running off a few would cost. The only pain with sand casting is there is a bit of cleaning up to do later if you want a really smooth finish. Having said that the raw cast look does have an appeal too. I guess that is where CNC machining has a big advantage - clean, perfect reproductions every time.
Will this design catch more dirt since more exposed?
Minimal I'd say as it is tucked away so aerodynamically out of the way when in flight. It may create a mini air vortex causing my left boot to be sucked back into 1969. If so I'll be off to my Honda dealer to order the first CB750/4
I'm interested to see if there is any noticeable increase in noise with this end of the chain and sprocket more exposed.
Location: Santa Maria, CA Otherwise known as heaven on earth.
Posts: 1,797
Quote:
Originally Posted by AllanB
Rob, I'm not sure if he used one mold for both pieces - he was planning on doing it that way. Once I was happy with it he said there are options to reduce costs on mulit- casts. I may have a chat to see what running off a few would cost. The only pain with sand casting is there is a bit of cleaning up to do later if you want a really smooth finish. Having said that the raw cast look does have an appeal too. I guess that is where CNC machining has a big advantage - clean, perfect reproductions every time.
There are methods for producing a better finish on sand cast parts, one of which is called skin dried sand molds. It is a process where the pattern is rammed in a conventional sand mold, but once it is removed a mixture of 10 parts water and one part molasses or lignin sulphate is sprayed onto the surface of the mold cavity in the drag or cope (whichever side holding the "inspection side" of the pattern) and dried with a gentle flame to drive out the water. The binder fills the voids between the sand grains and leaves a finish nearly the equivalent of investment casting. It takes some skill to do properly, but is an economical alternative to investment or permanent mold casting. Another alternative is to riddle French sand; a particular type that has a finer grain size and a higher percentage of clays; onto the pattern before the coarser sand is riddled and rammed. It will not make as fine a finish as skin dried, but takes much less skill to produce repeatable parts.
Past that it will be necessary to produce as many patterns as necessary to make more than one piece or set (in your case) of parts in one pour. I have used silicone molds taken from the master pattern to make multiple patterns from epoxy resin which will serve for runs of a couple hundred parts before degrading too much to use.
At any rate either will be preferable to CNC machining, which in this case would require a block of aluminum weighing 1.3 kilos to produce a part weighing less than 100 grams: very wasteful! Add to that the amount of time spent profiling the surface to a smooth finish. Machine time costs, and it would raise the cost of the part to an unacceptable height.
As an example the clamps for TharBars weigh 67% of the weight of the billet used to produce them: a very good number, and there is practically no profiling needed. Both of these properties were worked out with the assistance of the machine shop, and saved me a large amount of money per finished part.
Infinitely adjustable, made of the finest materials available, and completely sourced from local suppliers -- gotta support the local economy! Order today and know handlebar Nirvana.
Allen, i'm liking the rough finish, i want one! let me know how much it would be to get one poured. my current plastic cover is warped and getting worse, needs to be replaced asap.
Well spotted! After all the major earthquakes we have had here over the past year when the bike is parked up in the shed I place a brick front and rear of the back wheel, strap the bars to the rafters and bungee the sidestand down so if it jumps forward enough it will not retract. So many bikes were thrown over due to the force of the shakes
This method saved my bike in February's ripper.
Rob, I'm not sure if he used one mold for both pieces - he was planning on doing it that way. Once I was happy with it he said there are options to reduce costs on mulit- casts. I may have a chat to see what running off a few would cost. The only pain with sand casting is there is a bit of cleaning up to do later if you want a really smooth finish. Having said that the raw cast look does have an appeal too. I guess that is where CNC machining has a big advantage - clean, perfect reproductions every time.
Why don't you just bolt a drive-in wheel chock to the floor? Assuming your floor is concrete, anyway. Drive in, step off. Roll it back and away you go.
Oil filter - shit I change mine every oil change ............. and I use full synthetic oil. Bawahahahahahhaah
Cheers for the info Rob. I'll pop down and have a chat to the caster to see what he can get multi casts priced down too. We did discuss a very fine sand he uses if you want a super clean finish - if the cast has lettering for example. I saw some examples of brass casts made from a piece of etched glass - very impressive. It is a fascinating process ages old.
Why don't you just bolt a drive-in wheel chock to the floor? Assuming your floor is concrete, anyway. Drive in, step off. Roll it back and away you go.
A local bike shop had two bikes on display in front wheel chocks and both had damage front end damage due to the force of the quake. We had had a few severe buggers. My theory is my strapping etc allows for a degree of 'give' - it's saved the bike on a couple of occasions so far.
A local bike shop had two bikes on display in front wheel chocks and both had damage front end damage due to the force of the quake. We had had a few severe buggers. My theory is my strapping etc allows for a degree of 'give' - it's saved the bike on a couple of occasions so far.
Makes sense. Sounds like you need a padded cell for your 919, lol.
nice work..looks like a million
Will pay of course...
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