Author Topic: 30cc Flat Four (Puma)  (Read 19058 times)

Offline doubletop

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Re: 30cc Flat Four (Puma)
« Reply #210 on: November 23, 2019, 08:20:56 AM »
I had a think about how I was going to create some registers on the camshafts for the timing pulley grub screws and still maintain the correct orientation. I had in mind some sort of jig that I could use to lock the camshaft and crankshaft orientation, move the pulley out of the way and create the flats at the witness marks left by the grub screws. Amongst other things major problem was the ends of the camshafts, that held the ignition magnets were just not long enough to accommodate the clamp and get they pulley out of the way.

I had already added a second grub screw at 90deg to the original so it occured to me I could remove one grub screw and insert a drill down the hole to put an indent on the shaft. Replace the grub screw and do the second.



The problem with that would have been the possibility of damaging the thread if I used a twist drill.

I’ve used 6ba grub screws for which the tapping drill size is 2.3mm I have some 2mm piano/music wire so decided to try a D bit. The advantages being that I could grind the end to the 90deg of the tip of the grub screw and there would be less chance of damaging the threads.



The brass collar is a stop set for a 1mm indent in the 4mm camshaft.

I had thought that piano wire is capable of being hardened and tempered like silver steel. It proved not to be the case. Case hardening with “Cherry Red” (Kasenit equivalent) did the job.



The indents were done ‘in situ’ so the timing didn’t get disturbed. The drill vice used to clamp the two shafts together and stop them moving. It was all very easy in the end

Pete
« Last Edit: November 23, 2019, 10:07:37 AM by doubletop »
?To achieve anything in this game, you must be prepared to dabble on the boundary of disaster.? - Stirling Moss

Online Vixen

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Re: 30cc Flat Four (Puma)
« Reply #211 on: November 23, 2019, 10:40:40 AM »
Hi Pete
It often happens that way. Your greatest fears can turn to nothing. Making an end cutter fromm piano wire is a brilliant idea. If you have room, try to fit a second grub screw on each hole to lock the one below. It works very well.

Mike
 
It is the journey that matters, not the destination

Oh! sod the journey, lets hit the bar and pool instead.

Offline Admiral_dk

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Re: 30cc Flat Four (Puma)
« Reply #212 on: November 23, 2019, 09:08:07 PM »
I'm happy to hear that you found a useful solution and sorted the problem  :ThumbsUp:

Offline Art K

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Re: 30cc Flat Four (Puma)
« Reply #213 on: November 24, 2019, 03:17:10 AM »
Pete,
That was a good run. I like the RC controls for the throttle, to me that seems like a novel solution to throttle control. I have no doubt you will sort out the remaining problems & have a steady dependable runner.
Art
"The beautiful thing about learning is that no one can take it away from you" B.B. King

Online Roger B

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Re: 30cc Flat Four (Puma)
« Reply #214 on: November 24, 2019, 08:02:35 AM »
That looks to be a good solution  :ThumbsUp:  :ThumbsUp: Fine camshaft timing is always difficult in these sizes. If you can find a way to fit a 60 tooth gear it all becomes much easier as one tooth is 6 degrees and two keyways offset by 3 degrees allows adjustment to 3 degrees. The camshaft sprocket on my old Triumph had two pairs of fixing holes offset from the teeth such that by turning the wheel around you could get 1/4 tooth resolution.
Best regards

Roger

Offline doubletop

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Re: 30cc Flat Four (Puma)
« Reply #215 on: November 29, 2019, 09:10:51 AM »
Art

The servo controlled throttle idea comes from a project I had going a few years ago where I had the ignition controlled by a PIC microcontroller using an in-plug coil unit for the HT. The idea was that the ignition parameters could be adjusted, real time, on a running engine. The micro controller was used to set the throttle  position and then the advance adjusted to the best running position and then the data saved. The advance curve could then be setup across the rev range. It sort of worked but the engine under test, my single cylinder Lynx, wasn't that reliable and I got bored. Now I better understand what I should have been doing I may resurect it.

Roger

Interesting that you say that because it crossed my mind as I recalled something similar from my car tinkering days. I could well have been a Triumph. I've a picture of it in my mind.

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

Offline Jasonb

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Re: 30cc Flat Four (Puma)
« Reply #216 on: December 22, 2021, 08:07:08 PM »
Pete's Puma is now in Print  :)

Offline doubletop

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Re: 30cc Flat Four (Puma)
« Reply #217 on: December 28, 2021, 07:04:29 PM »
Pete's Puma is now in Print  :)

We'll that is a nice surprise!! I was wondering when Martin was going to print the article as I sent him the draft a while ago. With the supply chain issues my copies of ME don’t get to NZ until weeks, even months, after the publication date.

I’m looking forward to seeing it

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