Porsche 917 flat 12 engine

Help Support HMEM:

Foketry

Well-Known Member
HMEM Supporter
Joined
Sep 12, 2014
Messages
559
Reaction score
1,187
Location
Modena (motor valley) Italy
Another step forward for camshaft
I have temporarily installed the camshafts complete with bearings, aluminum spacers , gear ,intake and exhaust cams , now are locked in position by M3 grub screw .
Still to be done: timing, drilling hole for spring pins to lock cams on the camshaft, complete disassembly, cam hardening, final reassembly.

IMG_2213.JPEG
IMG_2214.JPEG
IMG_2215.JPEG
IMG_2216.JPEG
 
Last edited:

Foketry

Well-Known Member
HMEM Supporter
Joined
Sep 12, 2014
Messages
559
Reaction score
1,187
Location
Modena (motor valley) Italy
Gearbox, lost PLA
To make the gearbox castings I used the lost PLA system. I therefore designed the gearbox in 2 parts , + 2 covers and a connecting flange with engine
Gearbox has a smaller scale than the engine, it would get too long.
I will hide the ignition system in here and perhaps the oil pump if the one provided inside the engine block will not be able to pump all the necessary oil
No internal gears , differential and clutch, it will be a fake...

Cambio.jpg
Cambio sopra.jpg
Coperchio.jpg
 
Last edited:

ddmckee54

Well-Known Member
HMEM Lifetime Supporter
Joined
Jul 8, 2009
Messages
340
Reaction score
61
Foketry:

Those castings look great. You should post some of your castings on thehomefoundry.org. They have a Lost PLA forum and I'm sure the guys there would be interested in this work.

I've got a couple of questions:
1) What do you use for an investment? You say plaster but it almost looks too grainy for plain plaster, sand added maybe? Is this something you bought, or is it a home-brew?
2) How do you pour into the molds? In your picture of just the molds, it looks like the molds are open topped. But in your picture with the molds in the burn-out oven it looks like there's been something added to the top of the molds. Did you add some type of a pouring basin?
3) You show approximately 4 hours at 550, I'm assuming 550°C? Any ramp up time, or ramp down time, or is that your entire burn-out schedule?
4) Do you pour immediately after burn-out with the mold hot, or do you cool the mold?
5) Do you use a vacuum assist during the pour?
6) How many attempts did it take to get the castings shown? If you are able to do this in one shot then thehomefoundry.org will definitely want to hear from you. They'll be jealous and want to know what you do to get such results.

Don
 

Foketry

Well-Known Member
HMEM Supporter
Joined
Sep 12, 2014
Messages
559
Reaction score
1,187
Location
Modena (motor valley) Italy
Foketry:

Those castings look great. You should post some of your castings on thehomefoundry.org. They have a Lost PLA forum and I'm sure the guys there would be interested in this work.

I've got a couple of questions:
1) What do you use for an investment? You say plaster but it almost looks too grainy for plain plaster, sand added maybe? Is this something you bought, or is it a home-brew?
2) How do you pour into the molds? In your picture of just the molds, it looks like the molds are open topped. But in your picture with the molds in the burn-out oven it looks like there's been something added to the top of the molds. Did you add some type of a pouring basin?
3) You show approximately 4 hours at 550, I'm assuming 550°C? Any ramp up time, or ramp down time, or is that your entire burn-out schedule?
4) Do you pour immediately after burn-out with the mold hot, or do you cool the mold?
5) Do you use a vacuum assist during the pour?
6) How many attempts did it take to get the castings shown? If you are able to do this in one shot then thehomefoundry.org will definitely want to hear from you. They'll be jealous and want to know what you do to get such results.

Don
the aluminum castings you see in the photos are obtained after the second attempt, the blue PLA mold are those of the first attempt, the castings were not of good quality, I had 2 types of problem, cracks in the plaster and the aluminum did not fill all cavities. In some areas the thickness is about 2.5 mm and if the temperatures of aluminum and plaster are not correct, the aluminum does not penetrate uniformly. I repeated the whole process turning the models upside down for slower cooling and more pressure.
I created a containment lip in the plaster to generate more pressure.
In the first attempt i used special foundry plaster, but i had cracks. In the second attempt I used a first layer of ceramic powder, using a brush to fill in all the small cavities, about 4-6 mm thick. I let the ceramic dry for 1 hour, I put each piece in a metal container (in case of cracks, the liquid aluminum remains inside the container and does not go on the feet). I then filled each container with inexpensive plaster, the one that bricklayers use.
I let it dry overnight, put the containers in the oven, 220 degrees C for 2 hours to evaporate the water, then 550 degrees for about 4 hours, this time depends on how much PLA has to melt and burn.
It is important in this second temperature step to turn the containers down to release the liquid PLA. When no more smoke comes out of the oven, the process is finished, the cavities in the ceramic return perfectly white and clean.
A blow with compressed air to remove powder and you can pour the aluminum. Very important, the plaster must remain very hot, so when you remove it from the oven you must have the molten aluminum ready. Once poured into plaster , it will take several minutes before solidifying.
Each container is housed in a bucket of sand, safety is important !
I did several tests with foundry plaster of different brands, I also bought plaster in England but I always had cracks problems , with ceramic powder I solved this problem.
I don't use vacuum pumps, a first layer with the brush avoids air bubbles but it could be useful.
I hope my tips are useful to you, but I am not a professional and surely someone else knows the subject better than me.
Needless to say that molten aluminum is very hot and dangerous, always use protective devices , on Youtube you see Indian foundries where very experienced men working without shoes and gloves, we are not so experienced and our skin is very delicate.....
I will visit the site you suggested to me, thanks
 

ddmckee54

Well-Known Member
HMEM Lifetime Supporter
Joined
Jul 8, 2009
Messages
340
Reaction score
61
A vacuum table would probably help the thin sections fill. But getting those results on your only your second attempt with these parts is no small achievement - it's a pretty big deal.

It sounds like you're using a combination of the ceramic shell method and the investment block method, to take advantage of the best of both worlds.

What ceramic power do you use? The slurries used for ceramic shell sound like they are much thinner than what you are using. It takes several coats of sand and slurry with them to achieve the 4-6mm thickness you mentioned. Usually with a substantial drying period between each coat.

How difficult is it to de-mold the part when it's cast? I know the plaster will pretty much dissolve in a bucket of water, but how hard is it to remove your ceramic shell?

I'm not doing any casting yet, but I've got several projects in mind where cast parts would be almost a requirement. I've got a 3D printer, and I'm getting better at 3D CAD, With Lost PLA increasing as a casting method I'm slowly picking up some of the required skills.

I agree with you regarding personal safety, common sense rules - liquid metal is UNFORGIVING. There'll be no "What happens when you pour molten salt into an aquarium filled with water?" type of experiments for me. I like my skin the way it is. In relatively one piece, and not boiled, broiled or baked.

Don
 

CFLBob

Well-Known Member
HMEM Supporter
Joined
Feb 10, 2018
Messages
798
Reaction score
214
Location
Central Florida
A vacuum table would probably help the thin sections fill. But getting those results on your only your second attempt with these parts is no small achievement - it's a pretty big deal.

It sounds like you're using a combination of the ceramic shell method and the investment block method, to take advantage of the best of both worlds.

What ceramic power do you use? The slurries used for ceramic shell sound like they are much thinner than what you are using. It takes several coats of sand and slurry with them to achieve the 4-6mm thickness you mentioned. Usually with a substantial drying period between each coat.

How difficult is it to de-mold the part when it's cast? I know the plaster will pretty much dissolve in a bucket of water, but how hard is it to remove your ceramic shell?

I'm not doing any casting yet, but I've got several projects in mind where cast parts would be almost a requirement. I've got a 3D printer, and I'm getting better at 3D CAD, With Lost PLA increasing as a casting method I'm slowly picking up some of the required skills.

I agree with you regarding personal safety, common sense rules - liquid metal is UNFORGIVING. There'll be no "What happens when you pour molten salt into an aquarium filled with water?" type of experiments for me. I like my skin the way it is. In relatively one piece, and not boiled, broiled or baked.

Don
I don't want to derail this thread because it's one of the best on the HMEM, but I'd like to learn more about this side of things. I have a small vacuum caster and kiln from doing some silversmithing. Nothing is big enough to cast any of these models, but I'm at least a little familiar with the process.

I went to go look around at the Home Foundry, but I'm getting a browser error, which seems to be one of those security certificate date things. The "advanced" tab in Firefox says, "The certificate for thehomefoundry.org expired on 2/15/2018." It seems that with being expired over three years, I shouldn't be the only person getting that, so do you know anything about that? Have you been there lately? Is there another URL or something?



Bob
 

G54AUST

Active Member
HMEM Supporter
Joined
Sep 14, 2018
Messages
25
Reaction score
12
Location
Victoria, Australia. (Great Southern Land)
G'day Bob.

I've just come from there, and returned after reading your post above, and have no probs with the site.

Have you tried a different search engine ???

Did you hold your tongue to the left when pressing the "enter" button ???


Regards,

Trevor,
Melbourne, AU.
 

Foketry

Well-Known Member
HMEM Supporter
Joined
Sep 12, 2014
Messages
559
Reaction score
1,187
Location
Modena (motor valley) Italy
A vacuum table would probably help the thin sections fill. But getting those results on your only your second attempt with these parts is no small achievement - it's a pretty big deal.

It sounds like you're using a combination of the ceramic shell method and the investment block method, to take advantage of the best of both worlds.

What ceramic power do you use? The slurries used for ceramic shell sound like they are much thinner than what you are using. It takes several coats of sand and slurry with them to achieve the 4-6mm thickness you mentioned. Usually with a substantial drying period between each coat.

How difficult is it to de-mold the part when it's cast? I know the plaster will pretty much dissolve in a bucket of water, but how hard is it to remove your ceramic shell?

I'm not doing any casting yet, but I've got several projects in mind where cast parts would be almost a requirement. I've got a 3D printer, and I'm getting better at 3D CAD, With Lost PLA increasing as a casting method I'm slowly picking up some of the required skills.

I agree with you regarding personal safety, common sense rules - liquid metal is UNFORGIVING. There'll be no "What happens when you pour molten salt into an aquarium filled with water?" type of experiments for me. I like my skin the way it is. In relatively one piece, and not boiled, broiled or baked.

Don
this is the ceramic powder I use such as investment casting :

This ceramic powder has the advantage, compared to plaster, it becomes much harder and heat resistant, but very difficult to remove from the piece of aluminum, water has no effect, you have to remove it in small pieces with a chisel and hammer.
 

Foketry

Well-Known Member
HMEM Supporter
Joined
Sep 12, 2014
Messages
559
Reaction score
1,187
Location
Modena (motor valley) Italy
I don't want to derail this thread because it's one of the best on the HMEM, but I'd like to learn more about this side of things. I have a small vacuum caster and kiln from doing some silversmithing. Nothing is big enough to cast any of these models, but I'm at least a little familiar with the process.

I went to go look around at the Home Foundry, but I'm getting a browser error, which seems to be one of those security certificate date things. The "advanced" tab in Firefox says, "The certificate for thehomefoundry.org expired on 2/15/2018." It seems that with being expired over three years, I shouldn't be the only person getting that, so do you know anything about that? Have you been there lately? Is there another URL or something?



Bob
I also had the same problem with Chrome and also with Microsoft Edge, it would be interesting to log in, but there seems to be a problem, a security and invalid certificates
 
Last edited:

Latest posts

Top