Four cylinder scale engine

[steamer]

Check out Shapeways.    3D Laser sintered parts for fairly cheap in stainless steel/bronze should work just fine.   Check out George's thread on his Holt 3 cylinder

Dave

[Vixen]

Hello Thomas

As Ian SC suggests, electroforming in copper is one alternative.

Steamer has also suggested 3D printed metal parts in stainless steel/bronze from Shapeways.

I have been investigating 3D printed metal for my exhaust system. Have a look at my recent topic http://www.modelenginemaker.com/index.php/topic,7391.0.html

The big problem with 3D printed metal parts is the unpredictable warping and shrinkage during the hot metal fusing stage which follows the printing stage.  You must anticipate errors of 2% to 4% in the finished dimensions, unfortunately they are not predictable.


Mike

[ThomasM]

Hello everyone,

Thank you all for the good sugestions i really appreciate that.

The sintered parts method sounds very interesting. I will keep that in mind for the future.
The only problem at his situation is that i cant do this at my homeshop. I want to make that part myself.

Electroforming sounds also very interesting and many years ago i experimented with an education kit to create a thin coper layer around a plastik part to chrome it after that. So it seems that electroforming could be possible in a homeshop but all the chemicals are rather expensive or not available for private use.

Professional ceramic  invesment slurry as you suggested was also on my own " problem solving list ". I searched the web for this and the only available source for this could indeed be suppliers for dental laboratorys.
But dont ask about the price. Also this expensive investment materials are ceramic based and i think i would run into big problems when the time comes to remove the material out of the part. I think ultrasonic would not work on such a small diameter. Plaster of paris could be dissolved whith a fairly cheap solvent and the help of ultrasonic while sodium silicate bonded sand can be removed by cooking the part long enough in boiling water.

As advertised i started to cast the manifold out of individual parts to be able to use sodium silicate sand for the outher shape and the core. I just burned out the first mould with my propane torch. The whole mould was red glowing and because it is so small the heat surely made it all trough and all the plastic is vapourized.

I am not sure if i can cast this mould today because its sunday but maybe i will test the patience of my neighbours.....

Best regards,
Thomas

[Brian Rupnow]

That engine was originally used in 1928 to 1931 Fords. Back in the early 1960's I had three or four different Model A Fords. It was a great little engine, the only chronic fault being that it leaked oil thru the rear main bearing seals. This oil would then migrate to the clutch plate, so that every time you let the clutch out became a new and exciting experience. Sometimes the car took off very smoothly. Sometimes the clutch engaged with a lot of chattering and shaking, which shook the entire car. Sometimes, just when you thought the clutch wasn't going to engage at all, it would "catch" at the very last moment and you either stalled the engine or took off so damned fast it would almost give you a whiplash.  Great job on the build.---Brian

[Vixen]

Hello Thomas.

A complete copper Elecroforming kit is available in the UK from Gateros          http://www.ebay.co.uk/itm/Bright-Copper-Electroforming-kit-for-plating-non-metals-/253099158892?hash=item3aede2ad6c:m:m5nSuHUPb3iLj1BOp8Osz8A

A 22.5 Kg sack of jewelry investment powder is available in the UK from H S Walsh (jewelry makers supplies)       http://www.ebay.co.uk/itm/Pioneer-Smoothcast-Extra-Fine-Investment-Powder-22-5-KG-Casting-Metals-TC0451-/253007797911?epid=24003895796&hash=item3ae8709e97:g:1doAAOSwN2VZTSJR

Maybe a propane torch for burnout produced too many hot spots

Hope this helps

Mike

[ThomasM]

Mike , that was the hint i probably needed. Everytime i looked for professional investment powder i found the ones at dental laboratory suppliers for a unbelivable high price. I also recognized the jewelery makers use this kind of stuff but  i didnt look at the pricing because i was thinking dental laboratory = expensive , jewelery = more expensive ....

I will order a sack of it and try it out. Meanwhile i can do other things such as experimenting with brass pours or machining something else when i have the time.

Did you already use this investment ?

Thanks again to all of you for all the advice ! I will keep you informed.

Best regards,
Thomas

[Vixen]

Hello Thomas

H D Walsh are an old long established firm of jeweler suppliers, Their products are second to none.

You still have the problem of providing support for the long central core. You could try pushing thin pins of the same material as the casting through the walls of the PLA before you pour in the investment. The casting should fuse with the pins, if not you can drill and tap some small plugs and afterwards file then smooth.

You should also think of building a burn out oven from loose fire bricks, that should keep the direct flame off the investment and also spread the heat evenly. It takes a long time.

Plenty to experiment with

Cheers

Mike

[ThomasM]

Hello everyone,

I followed your advice and purchased a bag of professional investment powder. This was the right decission because it makes the burnout progress a lot easier but not bullet proof. It is of course still possible to break the mould while burning out the PLA printed model.

The last weeks i  tried differend methods of breaking a mould before pouring and i was sucessful in every single of them.

I also bought a used electric burnout killn to make the burnout progess more controlable.

My last four attempts in casting the exhaust manifold where all with moulds which where gravity feed like the ones showed in my previous posts. On my last failed attempt i decided to switch to another technique.

This part asks for vacuum casting because of its thin walls and the overall shape.

So i have build a simple vacuum chamber to swich over to vacuum casting  for my future attempts ( hopefully not to much ).

My first attempt was today and it was a " successful fail ".

It was a fail because the manifold is not usable but also a success because the vacuum chamber worked very well and the casing was the best of all of my previous ones.

I think this is the way to go and it will lead to a sucessfull casting sooner or later.

I have used an empty oil spray bottle for the flask at my first attempt. Unfortunately i didnt do any pictures of this because i was to excited trying this new way to fail.

Pic. 1 : The vacuum chamber. I took care to use only combustible materials such as plastic tubing and chipboard. Only the two pieced sealing on the top which is closed after the flask is inserted is made from aluminium.
The vacuum is produced from a strong industry vacuum cleaner i usually use to clean my machines and shop.

Pic.2 : The casting after the investment had been removed. It is at least 90% complete so i call it a 90% success. The buble at left side of the picture is the top of the mould while pouring the investment. It is most likely only an air bubble in the investment. This casting defect is no big deal and i dont worry about that.

Pic.3 : Every single printing layer is visible in the casing. I believe this is a good sign and proves that the vacuum casing progress has worked.

Pic. 4 : The biggest problem is seen in this picture. It seems that the casing was only feed trough itself and the flow through the feeder stopped for some reason. I am not able to evaluate this exactly. The first thing i will do is to increase the diameter of the feeder in my next attempt.

Pic. 6 : I broke the casting while investigating the crack. Hopefully the enlargement of the feeder is also the solution for this defect.

Pic. 7 : The area wich didnt fill is a little mysterious for me. The core is covered with metal but why is it not copletely filled ? Maybe i have to increase the leght of my flask to bring this area more to the inside of the mould. Actually there was only a few millimeters of feeder leght over this section because the spay bottle i used to do the flask was a little short.

I will do more pictures on my next ( hopefully sucessful ) attempt to show more of the process.

Maybe some of you have other thougts about the casing defects ?
I feel i am about to be sucessful.

Best regards,
Thomas

[ThomasM]

Hello !

I finally did it !

After i have done any possible mistake when designing a model for investment casting i sorted out the problems and was sucessful on the todays pour of the exhaust manifold.   

After switching from gravity feeded casting to vacuum casting the last remaining problem which you can see in my last post was a shrinkage problen due to the small feeder.

The solution was to increase the feeder to prevent it from solidification as long as possible. I also heated the top aera of the mould after pouring with a propane torch while maintaining vacuum for five minutes.

Here are the pictures :

1. The casing model whith investment already injected into the gas channel. There are also five little steel pins on the backside going trough the walls to support the investment core. The large feeder is a candle. I connected the pla model with hot wax to the candle.

2. There is not much clearence with the flask  i have made ( 60 mm diameter ).

3. The holes in the flask are temporarily closed with tape.

4. After pouring and solidification of the investment and removing the tape the flask is ready for bourning out the wax and pla model. This takes four hours after increasing the temperature of the electric burnout killn up to 700 degrees within the first two hours.

5 - 6. Total happyness after the pour. The manifold is complete with no defects and ready for finnishing.

Now i am back in business. I wil keep you informed.

Best regards ,

Thomas

[Myrickman]

Nice work Thomas....that was quit an accomplishment to get a good useable manifold casting. Can't wait to see it fitted up to the block. Paul

[Art K]

Thomas,
That looks great, but I must admit that it isn't something I would attempt. Great work!
Art

[Roger B]

Excellent, way beyond me but excellent   

[ThomasM]

Hello everybody,

Thanks for your kind comments.
With the experiences i have collected with the exhaust manifold i was able to cast the intake manifold being successful at the first try.

The inner diameter of the intake manifold is only 5,5 mm and even smaller as it is on the exhaust manifold.
As you can see i painted the manifold to make a little contrast to the sandblasted exhaust.

I think i am gettig closer......

The pictures :

1. The red hot glowing flask after burning the pla model out shortly bevore inserting it into the vacuum box for pouring.

2. The manifold after removing the investment. The investment in the inner section has to be removed by driving a rotating steel cable which can follow the corners trough the manifold.

3. It is useful not to remove the sprues or risers to early. They are useful for clamping the part to be able to machine it.

4 + 5. The two manifolds bolted provissionally to the engine for my personal amusement .... 

Now i will continue with finishing the cylinder head and the distributor....

Best regards,
Thomas

[Dave Otto]

Impressive work Thomas.

Dave

[william johnson]

 :pinkelephant:I want one