My Metal Workshop

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AKinnunen

Registered
Messages
35
Reaction score
76
Location
Beijing
# of dives
200 - 499
CCR manual valve project

This is a small project since there's not much to do recently, waiting for COVID to end so we can travel again...

I serviced my CCR manual valves (MV) and found that it had leaked water inside. After further investigation, the leak was due to low tolerances, wrong shape O-ring cavities, and some machining and design errors. Saltwater has gotten to the inside valve and already caused damages. I lost my interest in installing parts together and decided to make a new valve.

SF2 valve system is copied from inflation valve so most likely there are the same parts in use. The idea is good, but like all SF2 parts, tolerances are very low which leads to leaks all the time.

I redesigned the SF2 MV so that the outside shape (which I like very much) is similar to before, but with all other parts being new. I also increased the O2 flow a little because I feel that the original is too little. I also dream that my CCR is traveling weight <20kg (with tanks), which is why I took out weight wherever possible.

In the first version, all parts were titanium and I used previous valves from a number of dives until my friend from Germany asked me "are you stupid? You use titanium with pure oxygen…". After further study, maybe it was a bad idea after all, but even some brands use titanium for the 1st stage (O2 limit 40%) I thought. Since I couldn't see any visual changes in the parts after use, I decided that safety comes first so I changed the materials to aluminum and stainless steel. This was also a good chance to test hard oxidation for AI parts for future projects. The one negative being that black is the only color that you can use. All of the tolerances and O-rings are designed to support a temperature from -20 to +40°C.

After machining, I spent a few hours polishing parts before coating. The final result was better than what I had expected! I also designed and made a few assembly tools to make assembly super easy (takes just a few minutes to get ready).

Changes I made:
- Both piston ends are supported, which prevents horizontal movement
- Tolerances and new design prevent water from entering the valve
- Bigger flow to oxygen valve
- Ports O-ring cavities design is fixed (based on ISO standard and standard O-rings)
- Added holes where water can come out from the knop and makes saltwater possible to wash out
- Longer thread to cylinder part. The original was only a ~3 rounds-thread
- Materials AI 6001-T6, AISI 304 and Ti Gr4

Summary:
The easiest solution is to order a new MV from the internet, but that's too easy for some of us. I don't use manual valves too often and this was a good lesson to learn that they also need service. Due to the quality of parts, the functionality of the valve is now super smooth and soft. I've used the new valves for only 25 hours, but it still works as well as any new valve. Let's see if there is any need to service it before a hundred hours of diving!

Photos:
  1. Some design pictures
  2. New valve
  3. Parts (first Ti version)
  4. Old (right) and New (left) cylinder parts. Some idea about original valve quality and note this was first service and opening!!.
  5. Water test (Underwater Grate Wall, Beijing)

  1. 1.jpg 2.JPG 3.JPG 4.JPG 5.jpg


Br:
Arto
 
More metalwork..
Travel-friendly Harness and Backplate

Since all of my dives require traveling (typically including flying to other countries), I optimize all of my gear to fit airline standards.
Here are some photos of my lightweight harness. I made a travel-friendly aluminum backplate, titanium D-rings and other metal parts. I went a bit overboard so I made different colors as well - I can change colors based on my mood now.
I also made a single tank adapter for fun dives, but typical I use this backplate for my CCR. The most lightweight for traveling is my titanium side mount harness, but my dream is to travel with a complete CCR with a traveling weight of 22KG (including bag).

Here are some photos:
1. My backplate project, the design phase
2. Some photos of the ready parts
3. Same hardens, different configurations
4. I made and tested a backplate with a radius - it also works very well and is very comfortable with a 3mm wetsuit

For future projects, I will use only hard anodizing so the color will always be black. Normal anodizing is a little too weak when using gears in saltwater.

Hopefully, this can give you some new ideas for your future projects.
 

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The finish work of the valve is beautiful.
 
absolutely gorgeous, maestro.
 
MCH-6 restoration project
This small project includes many DIY parts so I put them under this thread.
I found a rusty old Coltri MCH-6 compressor that had been in storage for a long time without use. The original user manual shows that the manufacturing year was 2010. Based on what I know about the history of this compressor, it looks like it was used for less than 100 hours.
However, this compressor has not ever been serviced or cleaned. A number of screws were missing and the rest were loose. I believe that the filter inside the tower was also original. When I got it, a packet was upside-down, the engine dropped and the compressor had new and old transportation damages.
1.JPG

Because all of the safety covers were broken, I designed and made new ones which were a bit stronger than the originals. At the same time, I re-built the compressor, sandblasted, and re-painted all the parts.
The aluminum parts I cleaned of old paint and anodized surfaces while steel parts got zinc coating. I washed all of the parts using an ultrasonic cleaner before assembly.
2.jpg

1st test
After assembly and new oils, filters, belts, new changes etc. I made the first run. The Honda GX160 was easy to start, it ran immediately after a year in storage. However, the first problem was the OPV that started to leak after 80bar. I can't adjust or service it so it has to be replaced. Otherwise, no other leaks so far (so far so good). The original filling hose/head is a little too simple, so I ordered new ones with a closing/relief valve.

2nd test
Everything is fine after the new OPV installation. It starts to work after 305bar, but the air smells bad! I believe the smell comes from the compressor being upside-down when I received it, and the oil had gone into the 1str stage air inlet. I ran the compressor for one hour without a filter, after that the smell is gone from what I can tell.
I'm still waiting for the PMV ordered from Italy to arrive since it's not available in China.

I maintain the relationship with my neighbors:
3.JPG

3rd test
Finally, I received the PMV. It is hard to understand why this is an accessory. You can find a lot of discussion about PMV in these forums, but to keep it short, you need it! It is easy to install, but it doesn't work at all. It leaks and even adjustment doesn't help. After investigation, I found out that the dimensions of the filter tower tube don't support PMV at all. Lower o-ring leaks all air through, which doesn't keep any pressure. It's infuriating to say the least.
So, I have to design and make a new tower (yet another delay and extra cost to this project- looking like it will be a disaster). I found several issues about the filter tower design, and actually it doesn't support PMV nor filter, but that's a story for another time. The filter tower is a high-pressure component so don't make it at home like I did.

4.jpg

4th test and fill up test
The new filter tower has now been installed and finally, everything works well. The tower is coated by hard anodization, which produces the black color. I adjusted the PMV to 140bar, it works now as it should. Finally, this project is ready for use! I also installed an hour meter to help future maintenance. The last task was to check performance. Records start from 140bar because I don't have a gauge in the filling hose (yet). The average filling speed was 77.7l/min, which is a good result. I removed the water twice during this test.
5.jpg

Summary:
I don't plan to use this compressor in the near future, but it was a fantastic project for the Beijing COVID-19 Autumn season. I will make an electric motor conversion kit next, and also some kind of wheels would be a good extra. (Electrical start is maybe too much?) If someone wants to make a similar project or plans to buy a used MHC-6, I want to say forget it. A new MCH-6 in Europe goes for 2,000 euros or less, and a used one + service is easily over 1,000 euro.

Here is a list of parts that I used, I converted the prices to USD.
You can find some parts for a better price, but I have to use what is available here. At least you can get an idea about the cost if you invest in an old compressor.

Honda GX160
  • Motor oil Honda 1l 7USD
  • Honda foam air filter 0.5USD
  • Gasoline can 5l (pro model J) 9USD (+gasoline 5.2USD)
  • Air filter spray oil free
Some tuning parts because rust or damaged
  • Muffler 12USD
  • Fuel tank 12USD
Compressor MCH6
  • Compressor Coltri oil ST766 1l 55USD
  • Coltri air filter SC000340 55USD
  • Coltri inlet air filter SC000340 27USD
  • Safety Valve 300bar 54USD
  • PMV 113USD
  • New filter tower + bottom cap 150USD
  • Filling head 230 bar 46USD
  • Pressure gauge + Cu washer(50 pcs) 22USD
  • Custom made Fan and belt cover 35USD
  • Old parts Sandblast and re-painting 10USD
  • Anodization and Zn coating 5USD
  • Hour meter 5.5USD
  • Spring under filter (10 pcs) 2USD
  • New screw and nuts 2USD
  • Driving belt (V-belt 800mm) 1USD
  • PVC hoses 5/6mm (2m) 1 USD
  • O-rings to tower(10 pcs) 0.5USD
  • Cleaning stuff 5USD
  • Storage box free
  • Total 629USD
Refurbished MCH-6
6.jpg
 
Small update on my compressor project:

I like the Honda gasoline motor (but my neighbors don't). I will need a gasoline version for traveling but at home, it is just too noisy to use.

I made a simple fast change bracket which is designed so that the shaft is exactly in the same line for both motor options. This means that the belt tension is the same and there is no need to adjust it. Motor change time is less than 10 minutes and only needs one tool.

2.2kW motor - electric motor RPM is 2800 (same as Honda). This means that the fill-up speed is around the same for both engines.

I'm very happy with the results. I can now fill up tanks indoors, make nitrox, and boost helium.

If someone is interested about El conversion cost
  • 1 phase Electrical motor 220V 69 USD
  • Switch 1 USD
  • Metal parts 45 USD
  • Assembly material 5 USD
Tot 120USD

Some photos are attached below:
Sketch.jpgEl conversion.jpg
 

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