Re: TB5 proposal

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I'd like to see some more of the real thing Pat. Any idea on a time frame when that will be? It really doesn't seem like almost an entire year has gone by already, my how time flies. :eek:

BC1
Jim
 
Yes, it has been one of those years for me, and I have been pursuing setting up a casting kit business since my other business has not earned any money this year.

It is a bit dicey to go a year without income, but I am sure more than a few here are experiencing the same thing. I think I finally have an upcoming project, so maybe a little cash flow in 2012.

I really have to catch up with TB5 using the 3D modeling since it has been so long since I worked on the TB5 engines, and I have to remember what I was doing, and figure out where I left off.

Maybe I can get out to the shop and get a little done tonight.

Pat J
 
I got my list straightened out for which engine needs what maching done, and who gets what parts.

I also got the 3D model complete, and that was a good refresher.

Maybe I can start making some real chips tomorrow.
(Edit: Virtual chips are much easier to clean up. ;) )

Pat J

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Finished silver soldering the remaining frames tonight (yes, I got some actual work done on TB5, don't faint).

The new torch works much better than the old one.

Now it is just a matter of machining work.

You can buy an entire torch kit with two regulators, hose, handle, tips, cutting attachment, etc. cheaper than you can by a replacement handle.

Pat J
 
Nice 3D models. :) :)

What program are you using?

Pat H (TB 4 & 6)
 
I am using 2011 Solidworks.
I needed to convert from 2D to 3D at work, and so decided to use the same program for model engine design.

I have seen similar results with Alibre, and I would have gone with Alibre if I did not also need the program for work.

It took me forever to rewire my thought process from 2D drawings to 3D modeling, but as others predicted, once you learn 3D, it is much easier from many standpoints than 2D, and 3D is especially useful once you start making changes after the engine is almost complete.

I look back now and wonder how I use to do engine designs in 2D (very slowly).

Pat J



 
I was able to get one engine completed for TB5, and it turned out ok, but then in December, as I started working on the remaining engines, I started having all sorts of issues with the frames, and problems with the hole through the crankshaft supports not being aligned properly, and the supports themselves not coming out the same size.

The cylinders look ok, and they are complete, but I am really unhappy with how the frames look, and so have been sitting on the TB5 build, trying to figure out what to do.

I decided to set up for castings last year, and have been building a furnace, which is a work in progress, but is functioning for the first time this week.

I have been trying to duplicate what others on the internet have done, which is to melt gray cast iron and pour it in the back yard. After much research on the net, and a whole lot of head scratching, I attempted a cast iron pour today.
I did not get the cast iron to melt, but it got very hot. I was afraid of melting my camera lens, and so the picture below is sort of a miss.

The problem was as others had told me, which is that it is difficult to keep the pressure up on the propane tank during heavy usage. I ended up wrapping heat trace cable around the propane tank, but that did not help, so I will have to go to plan "B" on that (not sure what plan "B" is yet).

Anyway, it struck me the other day that maybe I need to cast the TB5 frames and try again with those. At least I could maintain an accurate shape on both crankshaft supports, and would just need to drill an accurate hole through both for the crankshaft. So maybe I will try casting the TB5 frames. The other ones are just not something I want to send out.

Pat J

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A friend brought me some aluminum rims, and so I made a large ingot mold, and decided to try and melt rims.

As has happened so often in the past when I have tried to use scrap metal, I ended up spending 10 times more trying to use scrap than if I just purchased new material.

Some may have access to a lot of good scrap though, and if done right, it could be a viable source. The asbestos needs to be power washed off the old rims before they are melted, and all the lead weights removed, as well as the stem.

Problems I had were oxidation of the metal because I directed the burner directly onto the rim (not a good idea), and I miscalcuated the volume of the ingot mold, and so the metal overflowed into one big mass. :p
If I tried to melt rims again (which I will not), I would place the torch under the ingot mold, and away from the rim. I used a quicky furnace around the rim, which was made up of some fire bricks and a tent of ceramic blanket (sort of a makeshift afair at best).

I think most aluminum rims are either painted or clear coated, and it looked like this added a lot of trash into the melt, which is not good at all.

In the future, I will just use the AL356 from Budget Castings (California supply house).
It is very clean, and for the last melt using 356, I did not use flux or degasser, and did not even skim the slag, and I got a perfect pour, and a far better pour than when I prevously used degasser, flux, and then skimmed the slag, melting a glove in the process of skimming. Go figure.

Pat J

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I started to make a wood pattern for the new frames last night.

It was late, and I was tired, and so it went great until I glued the centerpiece in backwards, and it went downhill from there.

I generally make patterns with balsa and superglue, since you can build continuously and you don't have to wait for the glue to dry. Balsa is easy to sand and carve, and you can repair mistakes if necessary.

Having botched the wood pattern, I decided to just print a pattern, and so I printed the blue pattern shown below.

If the rain stops, I will get out the green sand and try pouring some frames.



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Are talking about a 3d printer?

If so can you tells us more about it?


Pat H.
 
Pat H-

I have a low-end 3D printer. I will not mention the manufacturer, since I am very unhappy with the unit, and have had enless trouble with both the hardware an software.

The only good thing about the low-end printers is the low cost of the material.

3D printers are like metal working machinery, you get what you pay for, although I must say you can get a very reliable and fairly accurate low-end lathe, and with the 3D printer I purchased, it is more of you get much less than you pay for.

I knew when I purchased the unit that low end 3D printers were not ready for prime time, but I really wanted to do some pattern making that was complex enough to warrant a 3D printer.

The process I use is to draw a part in either Alibre or Solidworks, then create a STL file, which is like a tool path file similar to CNC. The STL file then has to be processed by the printer's software, which is very slow, and a proprietery file is created and then sent to the 3D printer.

The printer has an extruder head that is heated, and a thin plastic material is fed to the extruder from a roll as the print head follows the tool path, similar to injet printer technology, but with a third (Z) axis.

I have sent out parts to be made on $25K machines via the internet, and those parts turn out extremely nice, but the cost is so high that it is difficult to justify unless you plan on sellling the part as a casting kit or just have money to burn. I can print a part for anywhere from 2-10 dollars, whereas the same part printed on a high-end machine may cost 100 dollars or more when you include shipping.

My machine is so unreliable that I generally use it only as a last ditch effort, and even on this frame part for TB5, the machine printed the bottom incorrectly, and I had to sand off about 1/4" from the bottom and glue on a piece of balsa filler. The surface finish on the high-end machines is extremely good, and on the low end machines the surface finish is considerably rougher. The method I use to correct the rough surface finish is to coat the outside of my 3D parts with a filler, and then sand lightly and paint. Some have mentioned using a solvent to smooth the exterior or a part, but solvents make some fumes that can cause some bad health problems, so I don't use solvents.

Also, you cannot just print the exact 3D model that you make using Alibre or Solidworks and expect to be able to cast that part. You have to add machining allowances and draft angles on the surfaces. The draft angles allow you to extract the part from the sand. When you print the part in 3D, you have to add a 1.02 multiplier for aluminum, or a 1.01 multiplier for brass/bronze/cast iron, since the part shrinks as the casting cools.

So in summary, I do not recommend a low-end 3D printer. If you really want a pattern, and cannot make it from balsa or other type woods, consider sending the part out to be printed on a high-end machine. If you forget or ignore the shrinkage, draft angle and machining tolerances, then your printer part will not be usable.

The process for making a pattern entails creating a 3D model, and then saving that part as a separate file for use as a pattern, and then adding draft angles, machining allowances, etc. If you modify your original 3D model to add the draft angles and machining tolerances, then your assembly does not work, so I use unmodified 3D model files to create assemblies, and then separate modified 3D files for patterns.

Pattern making is a little confusing at first, but you get the hang of it with some practice, and after you make a few patterns wrong.
 
Here are a few photos of a V6 engine printed on a high-end printer.
The 3D model for this part was not created by me, this is a sample that was shown at a printer seminar.

Note that this part is usless as a pattern, since the draft angle and machining tolerances have been ignored, but it does demonstrate what you can do with a $25K 3D printer.

The 3D printed part can be exactly like the real part down to the most minute detail, in fact you can scale down and print a full size engine if you want, but it can be challenging to keep all the fine detail unless you use a lost-wax type of casting.

The petrobond sand (petroleum-based sand) does capture a lot of fine detail, and unfortunately it captures so much fine detail that it will mirror the slightest imperfections in your pattern.



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There is so much misinformation about casting on the internet, I will mention a few myths, as well as some safety items that must not be ignored.

Almost everyone you see on the internet uses a degasser and flux when casting aluminum, and they always skim the slag off the top of the aluminum before pouring.
If you use petrobond, there is virtually no gassing, and you don't need to add a degasser. If you use a high quality metal such as aluminum 356 available in the US from Budget Castings, then you don't need to add any flux, and I don't even skim the slag, since clean 356 does not have any appreciable slag.

Heat the metal as fast as possible, and do not stir it in any way, since stirring can introduce things that may cause gas (in the metal).

Use a pyrometer to get the exact pour temperature. I usually pour AL around 1,350 F.
If you pour at a temperature that is much less than 1,350, then the metal will solidify before if finishes filling the mold.

And of course, don't stand over the furnace and breath in AL fumes, they are not good for you.

Everyone on the internet says that steel crucibles add contaminates to the aluminum, but I see no evidence of that, and I have been getting perfect castings using a steel crucible, as do many others on the internet. You can really abuse a 1/4" thick steel crucible, and it just keeps on pouring. You can very easily damage a clay or silicon crucible just by handling it or putting metal in it.

Anything that contacts molten metal has to be preheated to remove all moisture, and you can expect an explosion if you mix molten metal with anything that has not be preheated to dry it completely, such as metal added to a hot crucible, metal poured into an ingot mold, and metal poured onto concrete.

Below is an ingot poured from AL356. You can see that the metal picks up the mill scale pattern from the ingot mold, and also perfectly copies the pattern left by the weld on the end of the ingot mold. This pour did not use flux, degasser, or slag skimming (none of my pours do).

The good part about clean AL356 used with petrobond is that it accurately copies the surface of any pattern. The bad part of clean AL356 is that it accurately copies the slightest of imperfections in the surface of patterns, but the solution is to just make smooth patterns.


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Thanks, really appreciate the info ...

Some time ago I had the opportunity to use one at a local college.
Think it cost about 30K, project came out real nice.


Pat H.
 
Here is the filled, sanded and painted pattern for the TB5 frame.

I will try and pour today weather permitting.



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1st attempt at casting some frames today.

Not too bad, a few pourous spots, but usable.



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