The Bucket Foundry

[WilDun]

. Is there a chance for unmolding 0.75-1.0° or is this attempt waste of time?

I guess it will all depend on how much time you have and whether or not you are using a hardened mould (sodium silicate) as opposed to greensand etc.
I remember FLETTNER said somewhere that he used a (tidied up) original Kawasaki head as a pattern and he got it out of the sand by carefully 'tapping' it and wriggling it around till it could be withdrawn, - those production heads don't appear to have a lot of draught angle (or 'draft' as the Americans say) at all!
I reckon just try it and you'll know for sure - but, a few extra degrees in this case can't really hurt anything!

[husaberg]

I will try 2% for the first shot. The next thing is the mold slope for the fins. A mold slope with 1,5-2,0° is looking very roughly. Is there a chance for unmolding 0.75-1.0° or is this attempt waste of time?

Ask Neil.
I know a lot of the simple copy cast stuff is just "wiggled" to allow for the shrinkage factor.

I guess it will all depend on how much time you have and whether or not you are using a hardened mould (sodium silicate) as opposed to greensand etc.
I remember FLETTNER said somewhere that he used a (tidied up) original Kawasaki head as a pattern and he got it out of the sand by carefully 'tapping' it and wriggling it around till it could be withdrawn, - those production heads don't appear to have a lot of draught angle (or 'draft' as the Americans say) at all!
I reckon just try it and you'll know for sure - but, a few extra degrees in this case can't rally hurt anything!

He had to sand down each fin individually if memory serves. The stock Japanese stuff is likely diecast with a steel tool. which is why they gat away with intricate and fine fining designs try something like a euro sandcast maybe Maico or CZ Jawa or its ilk for appropriate drafts and what fining you would get away with. Brian Demarge mentioned he did or has a programme that analyses air cooled fining patterns effectiveness or something similar.If I quote him he might share.

I did some work on Enfield engine cooling if its any help

Stephen

Not sure of your Eng mod , but the design of the fins I can help I have some papers , on them somewhere

Stephen

No,,,,

Stephen

Actually it made me even more impressed by those old english designers ...just enough and no more !

[Michael Moore]

My friend Jeff and I have done some test molds with 2.25" tall by approx 1.5 degree fins. Some release paint that has AL powder in it helps a lot to get them out of SS or urethane binder sand but it still doesn't come out easy. That is with fins sections about 1.5-2" long and 3 fins on about .5" centers.

It looks like determining a good strip time to pull the pattern before the bound sand hardens completely will be important. Also, if you use the wrong paint on your pattern that reacts with the sand binder you won't get it out at all!



I'm going to make a couple of pneumatic matchplate vibrators to see if they will help get the pattern out. Once those are made we'll try pulling the test patterns out of Petrobond, though that may need some support wires inserted into the fins in the mold to support them. We'll see.

cheers,
Michael

[WilDun]

if you use the wrong paint on your pattern that reacts with the sand binder you won't get it out at all!

....... test patterns out of Petrobond, though that may need some support wires inserted into the fins in the mold to support them. We'll see.

I'm told you can get a Teflon spray coating, would that be of any use for spraying on the pattern? - Any of you guys here know the best place to obtain that?

How tricky would it be to put support wires in thin sections like fins?

Flettner, did your hip hold out ok?

[Michael Moore]

from here;

http://buickcity.blogspot.com/2010/0...-at-buick.html





It appears there were 700+ support wires in each mold.

cheers,
Michael

[ken seeber]

A few years ago, in an ill fated attempt to provide a better cylinder for the KT100J engine, using a much more accurate core set up and a shrunk in CNC machined liner, we used the original J cylinder as a pattern for the external. We wire cut an existing cylinder down the guts and back screwed these to 10 mm alum plates, which were then set into 2 pattern boxes (cope/drag). The actual fins, were spaced at 10, were 2.0 at tips and 4.0 at bases and had a max height of 76mm. This gives a 1.0 mm drop per side, equating to 0.75 degree = draft angle.

We smoothed the fins as best we could with emery on a flat steel strip. In some case we also laid in some bog to give a less undulating surface. To help reduce friction, we also doused the pattern with some Foseco (good old British name hey!) stuff called Slipcoat. Also added a pic of some other Foseco stuff for gluing cores, but I do know of others just using a hot glue gun successfully.

Anyways, using a cold box corebinder, they were a real prick. Despite rapping etc, the sand fins often broke. It seems that waiting for the stuff to slightly go off was better than letting it go fully hard. Maybe CO2 would have been better, but as we were not going to cast them immediately after making the moulds, I was concerned that the sand would go to shit, as per our earlier experiences.

My thoughts that I would go to at least 1 degree, and that Yamaha must have used the hot box method with nicely machined pattern fins.

[Flettner]

I'm told you can get a Teflon spray coating, would that be of any use for spraying on the pattern? - Any of you guys here know the best place to obtain that?

How tricky would it be to put support wires in thin sections like fins?

Flettner, did your hip hold out ok?

I use teflon spray you buy at say Supercheap but let it set properly don't be like me and be in a hurry. AND put a few coats on, don't be cheap (like me). The smoother the finish the better on fine tapers. 1 (per side) degree will work but you have to have everything in your favour. I have used wires before but your best bet is to try and keep the broken sand part intact and sand glue it back in place after the pattern is out and before you reassemble the mould. This sand glue is very good. Husa will know what is called, or Ken

Oxford dictionary ; cantankerous - bad tempered , quarrelsome, example - push starting a high compression TT500 with a soft ignition!
It was only our backup bike but we must have pushed that bugger a kilometer up and down the pits. Finally after warming up a sparkplug in the YZ first did it start!! Lucky we didn't have to use it. Meagan and I entered the Acerbis four hour as a team swapping riders after every lap, Meagan had a bad crash on her first lap but managed to get the bike home so I was forced to finish the rest of the day on my own. We got five laps in including Meagans lap. The hip performed floorlessly BUT I was well aware of it and rode accordingly, it's nice to ride now without that little man (or could be a woman) stabbing me in the hip with what felt like a knife all the time . By the end of the day the track was cut up very bad with huge holes, I am real glad I didn't have to use that TT. A fun day though.
And yes, Meagan is ok, she said when she finally managed to get up off the track she wasn't sure which bike to ride back out of the forest, as she could see two of them, mild concussion. That's why she wasn't allowd to continue.

[Flettner]

Where we got to on Friday, the FOS, just a bit of paint and a tidy up and it's ready to mould. Water jacket on this cylinder is botted around the outside. For reasons that will become apparent.
And the water jacket core box for the Zurg cylinder

[Flettner]

Same core for both sides on the Zurg. I think I will need to water core the "ears" as well, they may get hot.

[F5 Dave]

Hey good to hear the body working well and that your daughter is ok after her spill. Only got as adventurous as a road ride today but looking forward to getting out on the dirt bike.

Watch progress with interest.

[Flettner]

Hey good to hear the body working well and that your daughter is ok after her spill. Only got as adventurous as a road ride today but looking forward to getting out on the dirt bike.
.

All Hintz's have had a bang on the head at some time or other.
Good to hear you are on the mend, Aria two day trail ride is a good one. Mid Febuary.

[Frits Overmars]

I'm told you can get a Teflon spray coating, would that be of any use for spraying on the pattern?

If Neil does it, it must work. But you better make damn sure nothing of it stays behind in the sand. If you heat teflon it may reward you with a sniff of hydrogencyanid, aka Zyklon....

[Michael Moore]

Graphite spray is what I see people mentioning as a pattern release, not Teflon.

[Flettner]

Graphite spray is what I see people mentioning as a pattern release, not Teflon.

Or graphite powder, rubbed into the surface of the pattern, I think it's called Plumbago ?? parting powder, I certainly use that stuff to good effect.

[Michael Moore]

Yes, plumbago is the graphite parting powder. The spray can is a convenience for applying it. The powder sure makes a mess and you'd better not have an itchy nose while handling the old sock filled with dust.