Author Topic: 30cc Flat Four (Puma)  (Read 7439 times)

Offline doubletop

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Re: 30cc Flat Four (Puma)
« Reply #135 on: September 02, 2019, 10:44:30 PM »
Lovely job on those copper intake runners.---Brian

Thanks Brian

A bit of a saga with the manifolds. I was going to do them all in stainless, I had plenty of seamed ¼” tube and a shortish length of seamless. The seamed tube doesn’t bend very well and certainly not tight bends. With our dairy and wine industries one thing we don’t have a shortage of is stainless steel but the minimum I could purchase was 6metres for NZ$150. Malcolm’s write up for the Bobcat suggests copper so I decided to try that.

I made sure I had the dimensions correct for the jig plate for soldering. I did it in CAD and then checked the job. Drilled the plate and you’ll see it all ready to go in my previous photo. Soldered it up and then came in for dinner. After dinner, the job had cooled down, I took it off the jig and checked it against the engine. Too short by 7mm!! I’d used the dimension for the inner set of holes between the and inner and outer row. I am getting error prone these days and its beginning to bother me. Anyway, it all had to come apart and be done again, fortunately I managed to recover the central manifold.

As for the exhaust the short length of seamless tube was sufficient so I didn’t need to purchase any more. You’ll notice that I haven’t done the double bends as in my original CAD design as the pipework would have ended up too close the carburettor to be comfortable. If you are careful the 1/4" seamless stainless tube can be bent with one of these




Pete

?To achieve anything in this game, you must be prepared to dabble on the boundary of disaster.? - Stirling Moss

Offline Brian Rupnow

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Re: 30cc Flat Four (Puma)
« Reply #136 on: September 02, 2019, 10:58:22 PM »
I am always tempted to buy some Cerobond. It is a solid metal at room temperature, but liquefies at about 180 degrees. Supposed to be the cat's meow for bending small diameter tubing without kinking. You heat it up with boiling water until it turns to liquid, pour it into the tubes, wait for it to cool off and solidify, bend your tubes, then heat the tubes up in boiling water to pour the Cerobond out. It's like a lot of things---I've heard about it but never actually used it.

Offline doubletop

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Re: 30cc Flat Four (Puma)
« Reply #137 on: September 03, 2019, 08:02:16 AM »
I've used pipe bending springs for 12mm/0.5" upwards, when doing plumbing. I recently obtained some small dia tube springs at a club auction but they don't go up to 0.25" although 0.25" springs are available.

Cerobond I guess is Woods Alloy. I imagine that it would make the bending a bit harder so you still need a suitably sized bending tool

The other trick, with larger diameters, is sand.

Pete
?To achieve anything in this game, you must be prepared to dabble on the boundary of disaster.? - Stirling Moss

Offline Brian Rupnow

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Re: 30cc Flat Four (Puma)
« Reply #138 on: September 03, 2019, 10:06:28 PM »
I've been hearing that "fill your tubes with sand" song for 73 years. It never worked for me. I think that is an urban myth.

Offline Admiral_dk

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Re: 30cc Flat Four (Puma)
« Reply #139 on: September 03, 2019, 10:59:58 PM »
Quote
I've been hearing that "fill your tubes with sand" song for 73 years. It never worked for me. I think that is an urban myth.

I have seen my dad do it in my childhood and he was an office worker, but to be honest, I do not remember how good the result was other than it was useable .... I'm on shaky ground here, but ... copper tube ...? :thinking: - I do also remember that he spend quite some time to stamp (compact) the sand and the temporary end-caps into place ....

Offline doubletop

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Re: 30cc Flat Four (Puma)
« Reply #140 on: September 04, 2019, 01:56:08 AM »
I've been hearing that "fill your tubes with sand" song for 73 years. It never worked for me. I think that is an urban myth.

I must admit it probably didn't work for me when I was re-plumbing my house years ago so purchased a set of springs.

Pete
?To achieve anything in this game, you must be prepared to dabble on the boundary of disaster.? - Stirling Moss

Offline Art K

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Re: 30cc Flat Four (Puma)
« Reply #141 on: September 04, 2019, 03:39:34 AM »
Pete,
I just thought I'd throw this out there. When I made my Upshur single I modified the valve guide so compression pressure couldn't push it out. That made it shorter and harder to center in the bore. I used a sharpie to see if the guide was in line with the valve. Put the marker on the head at the valve face, spin the valve in the guide, you can at least tell, the shiny spot is where the valve is in contact with the head, the broader the more the valve is in contact. In my case I had to tap the guide into position, I doubt yours is so complicated. A quick and easy way to see how much of the valve is seating.
Art
"The beautiful thing about learning is that no one can take it away from you" B.B. King

Offline Admiral_dk

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Re: 30cc Flat Four (Puma)
« Reply #142 on: September 04, 2019, 11:21:40 AM »
I should have made clear, that I'm not sure my fathers result would have been considered a success for our use here - sorry ....  :-[

Offline doubletop

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Re: 30cc Flat Four (Puma)
« Reply #143 on: September 04, 2019, 09:12:45 PM »

Pete,
I just thought I'd throw this out there. When I made my Upshur single I modified the valve guide so compression pressure couldn't push it out. That made it shorter and harder to center in the bore. I used a sharpie to see if the guide was in line with the valve. Put the marker on the head at the valve face, spin the valve in the guide, you can at least tell, the shiny spot is where the valve is in contact with the head, the broader the more the valve is in contact. In my case I had to tap the guide into position, I doubt yours is so complicated. A quick and easy way to see how much of the valve is seating.
Art


Art

This engine has combined guides and seats that are pressed into the head. The only real risk is distortion of the seat as a result of the pressing. The idea is good though and I do have some bearing blue that would be ideal for a similar test.


I should have made clear, that I'm not sure my fathers result would have been considered a success for our use here - sorry ....  :-[


The geat thing about these forums is the opportuinity to provide suggestions and alternative approaches and it is then up to the reader to determine which is most appropriate for their purposes. In a way there are no bad suggestions, although they should be limited to things that are not at all dangerous.

Pete
?To achieve anything in this game, you must be prepared to dabble on the boundary of disaster.? - Stirling Moss

Offline doubletop

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Re: 30cc Flat Four (Puma)
« Reply #144 on: September 09, 2019, 10:43:56 AM »
Not a lot to offer by way of an update. The engine is all assembled and waiting for the replacement ignition unit to arrive. The tracking from China says it is on its way so we will see.

Quote


     2019-09-05 04:08 China, Shenzhen, Departure from country of origin. Your item is in transit to New Zealand



Although it's not a torpedo motor Jo has the opportunity to say "I told you so". When I was assembling it I used thread locker on the big end caps. It took some of the paint off so I had to strip it down again and remove the paint completely.



A lesson learned. The paint may have looked nice but had no real purpose.

Pete
?To achieve anything in this game, you must be prepared to dabble on the boundary of disaster.? - Stirling Moss

Offline Brian Rupnow

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Re: 30cc Flat Four (Puma)
« Reply #145 on: September 09, 2019, 09:53:43 PM »
I have only painted one of my thirty one engine models, and that was to make it resemble an engine I seen on the internet. The best and safest bet is no paint at all.  I do like the look of nicely painted engines, but I don't paint mine for the same reason you have found.---Brian

Offline bpudney

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Re: 30cc Flat Four (Puma)
« Reply #146 on: September 10, 2019, 04:51:10 AM »
For what it's worth I have seen pipes being filled with sand prior to being bent on an industrial scale.   They even had a mezzanine to enable the pipe to be stood up vertically for filling.  It was a routine procedure for anything over about 75mm bore, in copper, copper/nickel/iron, steel.  The largest pipe I saw was about 500mm diameter, 6 or 7 metres long....it took a lot of sand!! For bending the pipe was dogged down on a big cast iron floor plate and heated with two huge gas torches.  Just heating the pipe up took several hours.  The person responsible was a early 20s guy only out of his apprenticeship by a year or two.  There were two big windlass' hooked up to the pipe by chain.  The "Master" was like a conductor, he directed the heated, told the people on the windlass' when to do anything.  When the pipe was being bent he was leaping all over it, tapping here and there with a 14lb sledge, keeping any ripples, creases etc at bay.

Anyway, there you are filling pipes with sand prior to bending definitely is not a myth.  All this happened in a shipyard in the UK, in the 70s.
cheers
Bill

Offline tghs

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Re: 30cc Flat Four (Puma)
« Reply #147 on: September 10, 2019, 11:36:19 AM »
the larger the tube the better compacted sand will work, particle size and compaction,, scaling down the sand for smaller tubes could help,, in the mid 80's scale model ship combat started,, air powered guns aboard ships blasting BB's into each other,, to build the gun barrel systems small SS tubing with an ID of a BB (.177) needed tight 90 degree bends .. these bends had to allow the ball to pass smoothly.. cerrobend or woods metal  was used with a great success..I've used to make tight bends in small tubes.. pre-anealing the tubes depending on material.. the neat thing is for the most part it's a never ending product as once melted out of the bent tube with boiling water it will solidify to use again..
what the @#&% over

Offline Laurentic

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Re: 30cc Flat Four (Puma)
« Reply #148 on: September 10, 2019, 08:13:56 PM »
Like Bill and for what it is worth, I also saw a copper pipe being filled with sand and bent under heat in a London ship repair yard in the 1960's.  I spent a few weeks in the blacksmiths shop and they had a maybe 6" diameter pipe to bend to fit on some ship and that's how they did it - filled it with sand, compacted all the way during filling and then stoppered top and bottom, and heated and bent.  Never forgot that.

They also re-white-metalled a big bearing - to suit a pin about 3-4 feet across.  When they set it up in the lathe and turned it down to size they collected all the white metal turnings and then melted it down and made white metal hammers for all.  I still have mine, a bit battered now but over 50 years old!

Chris

Offline doubletop

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Re: 30cc Flat Four (Puma)
« Reply #149 on: September 17, 2019, 09:34:02 AM »
A bit of an up-date:

The 1200 grit silicon carbide 'tumbler powder' arrived the other day. I had been told it may be a bit fine as others had suggested 600 grit or 1000 grit. The 1200 grit did look a bit fine, finer than talcum powder, but I decided to give it a go.

Mixed with a bit of oil the paste seemed finer than Autosol but it did the job. With the valves, springs and caps in place and the ends of the valve stems held in a pin vice each head took about 5mins. Testing on the test jig they held 60 psi without any problem. When re-installed on the engine there is a noticeable 'notch' as each cylinder goes into and out of the compression stroke.

All I need now is the second ignition unit which apparently in in NZ and heading my way.

Pete
?To achieve anything in this game, you must be prepared to dabble on the boundary of disaster.? - Stirling Moss