Free 173 Best Homemade Tools eBook:  
Remove advertisements
Page 1 of 2 1 2 LastLast
Results 1 to 10 of 13

Thread: Can you make tools from plaster?

  1. #1
    [email protected] tonyfoale's Avatar
    Join Date
    Nov 2016
    Location
    Spain
    Posts
    494
    Thanks
    208
    Thanked 820 Times in 261 Posts

    tonyfoale's Tools

    Can you make tools from plaster?

    Once more this is a specialised tool for serious petrol heads.

    Background
    One of the principal ways of improving the power output of IC engines is to increase its ability to breath air. The mechanics of doing this is often called porting. This involves cutting metal away in the ports and sometimes adding material by welding or with epoxy. Some people such as myself are prepared to go further and do a lot of machining and other work to try and get the most favourable port shapes possible within the confines of original head castings.
    However, getting the optimum port shape is not straight forward and some trial and error is the norm. Various tools are used to help, a flow bench which measures air flow is the main one, but even with that it is possible to go down the wrong path and the result can be a ruined cylinder head. When I plan to do major modifications I use a different sort of tool which only involves minimal cost if I get it wrong. I make another for testing before attacking the real one. The difference is that the test head is made from cheap plaster.

    A specific implementation
    I race a Yamaha SRX600 in the US, this started life as a useful street bike with no racing pretensions so the ports were designed without all out performance in mind. It has 4 valves but the two inlets each have separate ports and carbs, unlike the usual 4 valve system of combining the ports into a single port.

    Can you make tools from plaster?-waiting-go.jpg

    Initially I did some quick modifications (away from my flow bench) which produced a useful power increase, but I was sure that more drastic work would produce a much bigger improvement. This would have been a big risk to the head because there would have been no way back to the original if it didn't work well. So I made my plaster tool.
    Firstly I had to make a tool to make the plaster tool. This task requires moulding the original ports and combustion chamber of the real head, this is a non-destructive job. There are many moulding compounds that are used for this, some are a two part mix which can only be used once but I use "Vinamold" which can be re-melted and used many times. Resins like polyester and epoxy which set rigid are not suitable for this process because you need a rubbery like material so that you can extract the moulds from the ports.

    Can you make tools from plaster?-port-moulds-01.jpg Can you make tools from plaster?-port-moulds-02.jpg
    Here we have ports moulds, the pink one is from a port with small modifications which showed a 10% flow improvement over the stock port moulded in white.

    Can you make tools from plaster?-chamber.jpg
    This shows the mould of the combustion chamber.

    To produce the plaster head I had to combine the port and chamber moulds as shown here.
    Can you make tools from plaster?-both-ports-02.jpg Can you make tools from plaster?-stock-port-02.jpg

    Air flow doesn't like to turn corners and so the best way to get good flow is to aim the port as close as possible to the back side of the valve. This requires raising the port as much as possible. The practical limit to this is breaking through into the lower valve spring seat area, which contains oil. In this case there is not enough metal to raise the port to that height, so I planned to bore out a hole where there was supporting metal and insert a sleeve.

    Can you make tools from plaster?-ports06.jpg
    This sketch shows the planned inserted sleeve, It can be seen how much straighter would be the flow path.

    In order to test this with my plaster tool I needed to cast the plaster with the same steep port alignment. To enable that I cut a Vee out of one of the port mouldings and glued it back with a steeper path. The other port mould was left stock which gave me a base for comparison and also a check that the plaster head gave similar flow bench numbers as the real metal head. I call that an "honesty" check.

    Can you make tools from plaster?-steepened-port-01a.jpg Can you make tools from plaster?-both-ports-01.jpg
    The first pic. shows the steepened port and the second illustrates the large change in port angle between the stock and modified ports.

    Now was the time to mount these moulds into a box for casting the plaster.

    Can you make tools from plaster?-moulds-box-02.jpg Can you make tools from plaster?-moulds-box-03.jpg
    Ready to go.

    Can you make tools from plaster?-plastercast-01.jpg Can you make tools from plaster?-plastercast-02.jpg
    Here is shown the plaster cast, in its box and when removed.

    Can you make tools from plaster?-plastercast-06.jpg
    The de-boxed plaster head awaiting the removal of the port moulds.

    Can you make tools from plaster?-plastercast-08.jpg
    Note the difference in the air entry height of the raised port compared to the stock one. The entry radius is to smooth the air entry and is common practice when flow testing.

    Can you make tools from plaster?-plastercast-10.jpg
    For the flow bench tests, the valve is opened in steps of 0.050" and the flow is measured at each step and processed in my own software. I find the quickest way to do this is to place different width spacers between the base and a collar on the valve stem.

    The plaster head was tested and modified and the cycle repeated a few times until I was satisfied with the results. The results were good enough for me to proceed with machining the head.

    Can you make tools from plaster?-srx-head-26.jpg Can you make tools from plaster?-srx-head-25.jpg
    Machining the port to receive the sleeve and the machined head.

    To be continued.
    Attached Thumbnails Attached Thumbnails Can you make tools from plaster?-port-inserts-05.jpg   Can you make tools from plaster?-port-inserts-02.jpg  

  2. The Following 4 Users Say Thank You to tonyfoale For This Useful Post:

    Carlos B (03-13-2017), olderdan (03-07-2017), Paul Jones (03-06-2017), Toolmaker51 (03-08-2017)

  3. #2
    [email protected] tonyfoale's Avatar
    Join Date
    Nov 2016
    Location
    Spain
    Posts
    494
    Thanks
    208
    Thanked 820 Times in 261 Posts

    tonyfoale's Tools
    Continuation.

    Can you make tools from plaster?-port-inserts-05.jpg
    Here are the sleeves to be shrunk into the head.

    Can you make tools from plaster?-port-inserts-02.jpg Can you make tools from plaster?-port-inserts-06.jpg
    Two views of the fitted sleeves.

    Can you make tools from plaster?-srx-carbs-02.jpg Can you make tools from plaster?-srx-carbs.jpg
    Comparison of original head to carb orientation and the modified version. It is fairly obvious that the air has a much straighter shot with the modifications.

    So how did the plaster tool work out. Well if I had not made it I probably would have made the same modifications to the real head and achieved the same results. What the plaster version did was to remove the risk to the real head of getting it wrong. It allows experimentation beyond that which would be practical with the real thing. If any experiments were unsuccessful and the plaster head was changed beyond repair then it would be a simple matter to cast another.
    The following comparative "before and after graphs of the flow through a single port show the degree of success achieved, this was all achieved without enlarging the diameter of the port, which is important to keep airflow velocity high which has several beneficial effects.

    Can you make tools from plaster?-comparison.jpg
    Last edited by tonyfoale; 03-07-2017 at 03:44 AM. Reason: Added forgotten pix.

  4. The Following 7 Users Say Thank You to tonyfoale For This Useful Post:

    Carlos B (03-13-2017), DIYer (03-08-2017), nashty1 (03-17-2018), olderdan (03-07-2017), Paul Jones (03-06-2017), Rangi (03-17-2018), Toolmaker51 (03-08-2017)

  5. #3
    olderdan's Avatar
    Join Date
    Jun 2016
    Location
    Devon UK
    Posts
    421
    Thanks
    912
    Thanked 804 Times in 272 Posts

    olderdan's Tools
    Fascinating stuff Tony, the graph result is impressive.
    A lot of tuners will keep their work to themselves to keep an edge, I like the way you share it with us.
    Regards
    Alan

  6. #4
    [email protected] tonyfoale's Avatar
    Join Date
    Nov 2016
    Location
    Spain
    Posts
    494
    Thanks
    208
    Thanked 820 Times in 261 Posts

    tonyfoale's Tools
    Quote Originally Posted by olderdan View Post
    Fascinating stuff Tony, the graph result is impressive.
    A lot of tuners will keep their work to themselves to keep an edge, I like the way you share it with us.
    Regards
    Alan
    Alan,

    Glad you like it. The results that I have achieved with my Aermacchi engines are much better, I'll dig out those results, but it took a lot of work to get that far. I have put much less effort into the SRX.
    I have no reason to have secrets. Almost by definition if someone has to copy your work they are lagging behind. Throughout my life I have always found the knowledgeable willing to share, those with secrets are usually hiding their own lack of knowledge.
    A funny story on that theme from the past. When I was about 16 or 17 I decided to build a frame for a racing bike, without prior experience I sought out the only bloke I could find in the city who had done this. His reaction was something like "Go away kid, it's a matter of knowhow, you either have it or you don't. If you have to ask then you don't". I guess he was wrong.

  7. The Following User Says Thank You to tonyfoale For This Useful Post:

    Toolmaker51 (03-08-2017)

  8. #5
    Imabass's Avatar
    Join Date
    Dec 2015
    Posts
    66
    Thanks
    0
    Thanked 112 Times in 33 Posts

    Imabass's Tools
    nice work. Skills that I can only dream about.

    One thing that I noted is that the angle of your carburetor has now changed. It was designed for a certain position. Now that you have changed that angle, the float may function differently and you may have issues with tuning the carburetor or the bowl leaking.
    Why buy it if you can build it.

  9. #6
    [email protected] tonyfoale's Avatar
    Join Date
    Nov 2016
    Location
    Spain
    Posts
    494
    Thanks
    208
    Thanked 820 Times in 261 Posts

    tonyfoale's Tools
    Quote Originally Posted by Imabass View Post
    nice work. Skills that I can only dream about.

    One thing that I noted is that the angle of your carburetor has now changed. It was designed for a certain position. Now that you have changed that angle, the float may function differently and you may have issues with tuning the carburetor or the bowl leaking.
    Way ahead of you. Have a look at https://dl.dropboxusercontent.com/u/...Amal%20Mk2.pdf

  10. The Following 2 Users Say Thank You to tonyfoale For This Useful Post:

    DIYer (03-08-2017), olderdan (03-08-2017)

  11. #7
    Imabass's Avatar
    Join Date
    Dec 2015
    Posts
    66
    Thanks
    0
    Thanked 112 Times in 33 Posts

    Imabass's Tools
    Quote Originally Posted by tonyfoale View Post
    nice! In your racing class, can you switch to EFI?
    Why buy it if you can build it.

  12. #8
    [email protected] tonyfoale's Avatar
    Join Date
    Nov 2016
    Location
    Spain
    Posts
    494
    Thanks
    208
    Thanked 820 Times in 261 Posts

    tonyfoale's Tools
    Quote Originally Posted by Imabass View Post
    nice! In your racing class, can you switch to EFI?
    No, not period.

  13. The Following User Says Thank You to tonyfoale For This Useful Post:

    olderdan (03-08-2017)

  14. #9
    Content Editor DIYer's Avatar
    Join Date
    Aug 2013
    Posts
    3,087
    Thanks
    338
    Thanked 666 Times in 604 Posts


    Thanks tonyfoale! We've added your Mold Forming Tool to our Motorcycle Engine category,
    as well as to your builder page: tonyfoale's Homemade Tools. Your receipt:




  15. #10
    Content Editor DIYer's Avatar
    Join Date
    Aug 2013
    Posts
    3,087
    Thanks
    338
    Thanked 666 Times in 604 Posts


    Thanks tonyfoale! We've added your Mold Casting Box to our Miscellaneous category,
    as well as to your builder page: tonyfoale's Homemade Tools. Your receipt:




Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Tags for this Thread

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •