Author Topic: 30cc Flat Four (Puma)  (Read 2351 times)

Offline doubletop

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30cc Flat Four (Puma)
« on: June 27, 2019, 11:10:53 AM »

I built the Malcom Stride Bobcat something like six years ago







When I was building it t occurred to me that the crank could easily accommodate another pair of cylinders in a flat four configuration.
 


It was put on the “to do” list. I did build the Lynx and then locomotives got in the way.
 
Jason and Brian beat me to doing a flat configuration but they both did a twin based on Malcolm’s Bobcat or Jaguar parts.

Jason’s Ocelot



Brian’s Opposed Twin



A year or so ago I needed to teach myself CAD and used Malcolm’s drawings as the basis for my learning. That didn’t get much further than the parts for the original Bobcat design and a bit of a lash up in the assembly package.

Fast forward to a few weeks ago an I picked it up again and did the drawings for the parts to make the flat four.





All Malcolm’s engines have drawing numbers -
 
Lynx - NE15S – Nemet 15cc single
Bobat – NE15IT - Nemet 15cc Twin
Jaguar - NE7.5S   - Nemet 7.5cc Single

Jason has followed the convention with

Ocelot - NE15FT Nemet 15cc Flat Twin

Its been a while but here we go and unless there is a reason or not using the name ‘Puma’ this is going to be
 
Puma - NE30FF Nemet 30cc Flat Four

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

Online Jo

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Re: 30cc Flat Four (Puma)
« Reply #1 on: June 27, 2019, 11:14:16 AM »
 8) I'll be following along

Jo
Usus est optimum magister

Offline doubletop

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Re: 30cc Flat Four (Puma)
« Reply #2 on: June 27, 2019, 11:38:31 AM »
….. and its not vapourware, I’ve made a start









I’m not promising rapid progress and there may be a few stumbles on the way. I’ve had to make drawing changes already. But I guess that’s to be expected.

Pete
« Last Edit: June 27, 2019, 11:41:59 AM by doubletop »
?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 #3 on: June 27, 2019, 12:29:00 PM »
You have made good progress since we exchanged e-mails the other week, Puma sounds good to me.

looking forward to see the belt driven twin cams turn out rather than the gear drive option, almost seems a shame to cover it up.

Offline b.lindsey

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Re: 30cc Flat Four (Puma)
« Reply #4 on: June 27, 2019, 02:57:08 PM »
Looks like a fine project Pete. Watching along here as well.

Bill

Offline Ye-Ole Steam Dude

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Re: 30cc Flat Four (Puma)
« Reply #5 on: June 27, 2019, 03:03:04 PM »
Hello Pete,

I will be following along on this build, looks like a great start already.

Have a great day,
Thomas

Offline Laurentic

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Re: 30cc Flat Four (Puma)
« Reply #6 on: June 27, 2019, 06:21:25 PM »
Looks an interesting engine already Pete, nice looking start, I'll be following this one along too.

Chris

Offline doubletop

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Re: 30cc Flat Four (Puma)
« Reply #7 on: June 27, 2019, 09:43:36 PM »
Thanks for your good wishes everybody.

I had to make a start before I posted anything. It would have been too easy to fiddle about in the CAD package tweaking this and that and then getting distracted by something else. Cutting metal makes a commitment to carry on. 

My emails with Jason the other week were around any problems he had experienced with his flat twin and whether I should continue with the flat four or consider doing it as a V4. I was concerned about oil in the cylinders, I have some thoughts and Jason has some suggestions so we'll get to that at some point.

Jason has asked about covering up the belt drive, I have considered that. The parts have arrived from Belting Direct and although I have allowed for the extra size adding a belt tensioner may be a problem. We'll cross that bridge when we get to it. Making a round bearing holder would certainly be easier and help with the setting up. I may well do that for now.

I don't like doing repetative work so making four or eight of everyting will be a challenge so posts here will be infrequent, I'll just show differences to Malcolms original design and sub assemblies as they are made. It won't be a blow by blow 'how to' guide. Malcolms original aricles did a better job than me on that and 90% of the parts are to his original design.

I'm waiting for the bearings to arrive so I'm on the cams at the moment. They need a bit of concentration.

regards

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 #8 on: June 27, 2019, 10:18:48 PM »
Doubletop--Very nice cad work. I wish you great success with the build and will follow along. I anticipated trouble with an oil base, just as Jason experienced with his twin. The revolving crankshaft picks up the oil and throws it into the cylinder on one side of the engine. I solved that issue by having a removeable cover-plate which let me give the crankshaft and rods a good squirt of oil from a can before I ran the engine.---Brian

Offline doubletop

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Re: 30cc Flat Four (Puma)
« Reply #9 on: June 27, 2019, 11:23:36 PM »
Brian

I'm planning a deeper sump so the oil has somewere to return to and I have discussed baffles with Jason. Simple plates with slots in for the conrods. They could well be integral with the sump.

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 #10 on: June 27, 2019, 11:46:36 PM »
Pete,
This looks like a great project and I will be following along. I totally understand taking your time, we will be here.
Art
"The beautiful thing about learning is that no one can take it away from you" B.B. King

Offline doubletop

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Re: 30cc Flat Four (Puma)
« Reply #11 on: June 28, 2019, 11:44:10 AM »
A chilly Friday night here in NZ so I tinkered with the CAD

Feasibility of adding the oil baffles and an alternative simpler exhaust pipe on the right hand side



And timing belts



More by luck than design, apparently the pulleys and standard belts I ordered will fit without the need for a tensioner. We'll see.

Magnet disks for the ignition should be easy to install and as Jason suggested the cover can be dispensed with.

Getting a bit ahead of myself though.

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 #12 on: June 28, 2019, 12:26:31 PM »
Exposed belts look good, a bit of tarting up of the plain pulleys may add a bit wow factor.

For the sump I was thinking of a trough, similar to what Graham has on these two engines and Jo's Seal & Seal major will have the same sort of arrangement. Once the oil in the trough has been flung out as the engine is started it can only flow back slowly through a small hole or two which limits what gets thrown about. Alternative with your deeper sump would be to have some oil flingers and keep the oil level below that of the crank and big ends so only a small amount of oil gets picked up.

http://www.modelenginemaker.com/index.php/topic,4680.0.html

Offline cnr6400

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Re: 30cc Flat Four (Puma)
« Reply #13 on: June 28, 2019, 03:34:21 PM »
Great looking engine CAD work!  :ThumbsUp: :ThumbsUp: :ThumbsUp:

One suggestion - Looks to me like the crankshaft pulley has about 90 degrees of "wrap" of the belt. I would suggest adding an idler pulley in the non-tension side span between crank and cam to get closer to 120-180 degrees of "wrap". This will reduce stress in the belt and lower the chance of skipped teeth as the belt warms up at high rpm. Just food for thought, I've designed some timing belt systems for a few companies, and had the hoo-ha's with low wrap / high load situations.

Offline Allen Smithee

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Re: 30cc Flat Four (Puma)
« Reply #14 on: June 28, 2019, 08:07:02 PM »
Slightly surprised you went for two camshafts - surely with a two-throw crank (so the left and right cylinders are alternate-firing) you only need one camshaft?

AS
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Offline doubletop

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Re: 30cc Flat Four (Puma)
« Reply #15 on: June 28, 2019, 11:31:31 PM »
Thanks for the feedback, that’s why we are here.

Jason - Now I understand what you meant by the curved baffle; I was planning to ask you. I've been away from here for too long and have missed following what others have been up to. It certainly looks like the solution. As well as limiting the amount of oil thrown into the bores it will direct it at the cams. In fact, when I was boring the crank case I had considered leaving the curves in place at the sides and leaving the camshafts in their own separate bore. There would have then been a lubrication problem to solve for the camshafts. I thought that was a step to far at this point and went with Malcolm's approach of a fully opened out crankcase.

cnt6400 - Thanks for the advice. The belt I'm using is a standard 145mm I had expected a bit of slack that needed tensioning but the CAD package tells me not. If I went to the next size of 165mm I could add a tensioner. We'll see when I've got the crank and camshafts in. I've yet to make them and can't dummy them up as the bearings haven't arrived yet.

Allen - Yes; that was my first thought and started out on that route. With a single centralised camshaft the tappet guides would have been quite long, but not really a problem. However, I think the crank would have fouled the camshaft. I could have moved it up a bit and had the pushrods at a slight angle. Not wanting to make too many changes went for twin cam to keep it as close as I could to using Malcolm’s original components.  Given a cylinder configuration of 1. front left, 2. rear left, 3 rear right 4 front right.  A single camshaft would give a firing order 1,4,2,3 with 2 camshafts you have the opportunity to do 1,3,4,2 which may be a bit more balanced. Whatsmore a 30cc Flat Four Twin Cam is a bit more sexy.

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 #16 on: June 29, 2019, 02:14:48 AM »
Pete,
The only thing that I would throw in the mix, not to muddy the water though. Is that most full sized flat fours have a crank much like a inline 4 the end throws up and the center two down. I did see another flat 4 build that had the same crank configuration as you're planning so I know that it works.
Art
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Offline Jasonb

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Re: 30cc Flat Four (Puma)
« Reply #17 on: June 29, 2019, 07:22:09 AM »
. Whats more a 30cc Flat Four Twin Cam is a bit more sexy.

I think that sums it up well, when designing an engine that won't really be put to work so weight, performance, etc are not such an issue the designer can just go with what they fancy. If I remember rightly I had to move my single cam slightly further away from the crank and had to alter the gear teeth to suit.

The Jung's flat 4 model has a similar crankshaft arrangement so you should be OK. Malcom did do several articles about crank designs and balance as a build up to the Bobcat series and goes into detail why he opted for a flat crank.

Offline bruedney

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Re: 30cc Flat Four (Puma)
« Reply #18 on: June 29, 2019, 08:00:09 AM »
Following along Pete.

Look forward to seeing it in the flesh sometime.

Where are you getting your bearings from? I source bearings from NZ Miniature Bearings if I am not wanting to wait for them to come from Aliexpress sellers

Cheers
Bruce
‘Results! Why man, I have gotten a lot of results. I know several thousand things that won’t work.’ — Thomas Alva Edison

Offline doubletop

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Re: 30cc Flat Four (Puma)
« Reply #19 on: June 30, 2019, 10:48:01 AM »
I'm happy that the crank, as proposed, will be OK it will allow a cylinder to fire every half rev so that would balance everything out without needing any balance weights. Again, we'll see.

Bruce - the bearings are coming from Bearings Direct in the UK. Unfortunately, NZ suppliers seem to be overly expensive and although Aliexpress are cheap their delivery timing can be a bit hit and miss.  I may be taking it to the club night on Wednesday.

This weekend has been a bit of a mission in making the cams. After a failed attempt I ended up with two good blanks. Then I struggled to get the rotary table line up accurately on the mill. Leaving it until the next day I had it done in 30 mins. I then made a start on machining the cam profiles but realised, after about 30 steps, I was going the wrong way! That required another blank making.

Malcolm’s cam table only shows the 120steps between 300->0>60 degrees. The base circle is another 240 steps so with two blanks 720 steps plus the wasted so about 750. (No need for suggestions of CNC thanks, I get it. This isn’t the first job I’ve done that I’ve been winding handles for hours mentally adding CNC to the to do list.)

Malcolm suggests cutting the profiles using the Z axis of the mill. I did that the first time round but as you are cranking the weight of whole mill head up and down, at times only 0.01mm, I found it less than satisfactory. This time I used the Y axis and had far better control. However, it does require the rotary table and fixed centre to be set up accurately along the X axis. If you use the Z axis you just need to ensure the height of the centre is accurately set. Alignment along the X axis isn’t that important. Maybe that’s why Malcolm suggested doing it his way?







So I’ve now got 8 cams ready to be separated the bosses trimmed to length and the holes drilled and reamed, then that’s another of bigger jobs done.

Pete


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

Offline MJM460

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Re: 30cc Flat Four (Puma)
« Reply #20 on: June 30, 2019, 12:34:46 PM »
Hi double top, a great thread, I am enjoying following along. 

Don’t worry too much about rotating the wrong way when you were making that cam.  In my working life, I was in an office of a very large company who were making steam turbines.  In the foyer was an example of their work, a turbine rotor, about five meters long, with the smaller parts of the shaft over 300 mm dia, and the blades ranging from around four cm long, not very long as it was obviously a very high pressure turbine rotor, as an example of the work they do.  All machined in one piece from a single forging.

I asked how it came to be available to put on display.  Apparently it was machined to rotate in the wrong direction!  It happens to the very best of us.  You can put yours on display beside the engine at a show.

MJM460

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Offline Allen Smithee

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Re: 30cc Flat Four (Puma)
« Reply #21 on: June 30, 2019, 08:31:52 PM »
Great stuff - really appreciate you sharing. Can I ask a question (I want to understand so I can copy ideas for my own projects!)?

Do I understand correctly that these blanks will each be cut up into four individual cams, each of which will then be bored and mounted on a shaft? If so how will they be fixed to the shaft - press fit, bonding, pinning, silver soldering or something else?

And would each resulting camshaft than be carried in two ballraces, one at each end?

Thanks,

AS
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Offline Brian Rupnow

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Re: 30cc Flat Four (Puma)
« Reply #22 on: June 30, 2019, 09:00:00 PM »
Allen--They are attached to the shaft with Loctite. It holds fine, and an added benefit is that if you install the cam segments ass backwards as I did, a little heat from a torch frees them up very easily and lets you turn them around.---Brian

Offline bruedney

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Re: 30cc Flat Four (Puma)
« Reply #23 on: June 30, 2019, 09:35:45 PM »
Bruce - the bearings are coming from Bearings Direct in the UK. Unfortunately, NZ suppliers seem to be overly expensive and although Aliexpress are cheap their delivery timing can be a bit hit and miss.  I may be taking it to the club night on Wednesday.

Hi Pete
I find NZ Miniature Bearing very reasonable https://nzminiaturebearings.com depends on size and what quality you want. I have also found and Aliexpress supplier that is quite consistant in their shipping https://fushi.aliexpress.com/store/511615?spm=a2g0s.9042311.0.0.27424c4dZsZPaM
I hope to be there on Wednesday but depends on how things go today and the next couple of days. Lee's mum passed away last week and the funeral is today.

Regards
Bruce
‘Results! Why man, I have gotten a lot of results. I know several thousand things that won’t work.’ — Thomas Alva Edison

Offline doubletop

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Re: 30cc Flat Four (Puma)
« Reply #24 on: June 30, 2019, 10:01:09 PM »
Bruce - Sorry to hear about Lee's mum, hopefully I'll see you on Wednesday. On the bearings I'll admit to a bit of laziness. The bearing specs in the ME article for the Bobcat have an error so I went back to Bearings Direct to check what I had ordered last time. As I was there it was too easy to just re-order.

MJM460 - In my case if I had been on the turbine rotor job the 4cm blades would have been 2cm. I moved the Y axis in rather than out from the initial cut for the base circle. I was going well and went in for lunch and when I came back to the job I realised what I had done.

Alan - Yes ball races each end you can see them in the CAD pictures. Brian has answered you on the fixing of the cams. As he says the benefit being if you stuff it up you can go again. Given I'm doing two shafts with different firing order there's plenty of opportunity to do that. Fixing the cams to the shaft will be some time off yet and be done when I confirm the firing order and ignition so the whole thought process is done in one session. I did the cams now just to get a tedious job out of the way.

Pete
« Last Edit: June 30, 2019, 10:06:48 PM by doubletop »
?To achieve anything in this game, you must be prepared to dabble on the boundary of disaster.? - Stirling Moss

Online Jo

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Re: 30cc Flat Four (Puma)
« Reply #25 on: July 01, 2019, 07:24:52 AM »
On the bearings I'll admit to a bit of laziness. The bearing specs in the ME article for the Bobcat have an error so I went back to Bearings Direct to check what I had ordered last time. As I was there it was too easy to just re-order.

I see what you mean Pete  :thinking: , the article starts by saying they should be 68000 bearings they clearly added one too many zeros at the end  :Doh: Maybe they got confused that it needed an extra numeral as the next bearing they quote is the 61800  :headscratch:

I can't see why you would choose the 61800 over the 6800, they are both open deep ball bearings of the same dimensions  :noidea:

Jo
Usus est optimum magister

Offline doubletop

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Re: 30cc Flat Four (Puma)
« Reply #26 on: July 01, 2019, 08:26:39 AM »
On the bearings I'll admit to a bit of laziness. The bearing specs in the ME article for the Bobcat have an error so I went back to Bearings Direct to check what I had ordered last time. As I was there it was too easy to just re-order.

I see what you mean Pete  :thinking: , the article starts by saying they should be 68000 bearings they clearly added one too many zeros at the end  :Doh: Maybe they got confused that it needed an extra numeral as the next bearing they quote is the 61800  :headscratch:

I can't see why you would choose the 61800 over the 6800, they are both open deep ball bearings of the same dimensions  :noidea:

Jo

 Jo

Worse than that the  bearing should be a 6801 12x21x5 not 61800 10x19x5  as stated in the ME article

.... and now looking at the invioce I didn't get them from Bearings Direct I've ordered them from Simply Bearings.

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

Online Jo

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Re: 30cc Flat Four (Puma)
« Reply #27 on: July 01, 2019, 09:29:49 AM »
 :facepalm: See what you mean Pete. Looks to be two bearings of 19mm O/D and one of 21mm O/D. I did wonder why in the parts list they had broken the bearings out over two lines and then quoted the same numbers rather than just having one line.

At least they are not too expensive if you get caught by their mistake and have to buy another set  ::)

Jo

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Offline doubletop

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Re: 30cc Flat Four (Puma)
« Reply #28 on: July 02, 2019, 10:33:10 AM »
Following along Pete.

Look forward to seeing it in the flesh sometime.

Where are you getting your bearings from? I source bearings from NZ Miniature Bearings if I am not wanting to wait for them to come from Aliexpress sellers

Cheers
Bruce

Bruce

Thanks for the heads up. NZ Miniature Bearings are certainly cheaper and I could well have them by now had I gone to them.

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

Offline Ian S C

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Re: 30cc Flat Four (Puma)
« Reply #29 on: July 02, 2019, 12:53:47 PM »
When I buy bearings I use SMP bearings in Carlyle st Christchurch, their prices seem ok.
Ian S C

Offline doubletop

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Re: 30cc Flat Four (Puma)
« Reply #30 on: July 03, 2019, 10:33:07 PM »
When I buy bearings I use SMP bearings in Carlyle st Christchurch, their prices seem ok.
Ian S C

Maybe it’s the case that in the past NZ suppliers that offered a reasonable price were not obviously online so you couldn't find them. Or they have woken up to the fact that if they want to stay in business, they need to offer their products at an internationally competitive price. Hiding behind, "NZ is a small market" and "Shipping costs to NZ are high" just doesn't work anymore.

In my early days of this hobby I was looking for a something from Vertex. The best price I could get, landed in NZ, was from the UK. Ridiculous when the item was being shipped from Taiwan to the UK and then to NZ. In the end I found the Vertex importer and cut out the middle men, even then it was a similar price to getting it from the UK.

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

Offline Ian S C

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Re: 30cc Flat Four (Puma)
« Reply #31 on: July 04, 2019, 01:16:41 PM »
Got my 6" Vertex rotary table with dividing plates and tail stock in Christchurch, and direct from Taiwan about the same time as I got my lathe, also from Taiwan, through Paykels, now I think Blackwoods Paykel
Ian S C
« Last Edit: July 04, 2019, 01:24:01 PM by Ian S C »

Offline doubletop

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Re: 30cc Flat Four (Puma)
« Reply #32 on: July 05, 2019, 08:51:05 AM »
Got my 6" Vertex rotary table with dividing plates and tail stock in Christchurch, and direct from Taiwan about the same time as I got my lathe, also from Taiwan, through Paykels, now I think Blackwoods Paykel
Ian S C

Ian

The heavy stuff I  do purchase locally, lathe and mill. I got my Vertex rotary table direct through the NZ importer. A request to Vertex in Taiwan gave me his details. He didn't have stock, but I ordered anyway. It to only 4 days to arrive to me

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 #33 on: July 05, 2019, 08:52:30 AM »
A bit of an update

The cams were completed and case hardened with “Cherry Red” case hardening compound.



They’ve now been parked ready for the assembly of the camshafts, which I’ll do once I’ve got my head around it and confirmed the firing order and done the timing diagrams. I’ll do it all at the same time.

Next up was the crankshaft. I’m doing a built up crank the same I did with the Bobcat. I forgot to take a photo of the separate parts for the this crank so here they are for the Bobcat.



Here’s the Puma crank with the parts just pushed together.



And assembled with high strength Loctite 680



I assembled the cranks and webs first to get them into alignment and used the lathe to ensure the nose and tail were in alignment. Next will be drilling the webs and inserting pins to make absolutely sure it all stays together.

The next parts are the four conrods. I started on the blanks while I allowed the Loctite to cure.

I recently saw somewhere a suggestion to use a lathe tool in a fly cutter.  With a CCGT060204 ceramic tip the results were outstanding



So now  have four blanks ready for the next stages.




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

Offline Roger B

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Re: 30cc Flat Four (Puma)
« Reply #34 on: July 06, 2019, 10:35:07 AM »
Just catching up with this after having been away on holiday  :)  :)  :ThumbsUp: Looking good  :praise2:  I'm not sure of the need to mill the cams in 1° steps unless you have CNC. I have used 6° steps without problems.
Best regards

Roger

Offline doubletop

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Re: 30cc Flat Four (Puma)
« Reply #35 on: July 06, 2019, 10:38:35 AM »
Just catching up with this after having been away on holiday  :)  :)  :ThumbsUp: Looking good  :praise2:  I'm not sure of the need to mill the cams in 1° steps unless you have CNC. I have used 6° steps without problems.

Roger

You are probably right, and Malcolm suggested going in 2deg steps, but I wasn't going to try it and then wish I hadn't and have to start again.

It just added a few extra hours to the job as I was making two sets.

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

Offline Laurentic

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Re: 30cc Flat Four (Puma)
« Reply #36 on: July 06, 2019, 12:38:06 PM »
Pete, just out of interest, when you loctited the crankshaft together what clearance did you allow between pin/shaft and relevant bore in the web?  I was thinking too much and it's a weak joint, too little and then no space for the loctite?
Chris

Offline doubletop

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Re: 30cc Flat Four (Puma)
« Reply #37 on: July 06, 2019, 10:42:48 PM »
Pete, just out of interest, when you loctited the crankshaft together what clearance did you allow between pin/shaft and relevant bore in the web?  I was thinking too much and it's a weak joint, too little and then no space for the loctite?
Chris

Chris

It will be about 1 thou. The tail is 10mm ground silver steel and the hole was reamed. Since being glued I've now drilled the webs 2mm and inserted 2mm pins through all the joints. I did the same for the Bobcat and then for the crank for my 7.25" guage Dart. None of them have been a problem



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

Offline Laurentic

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Re: 30cc Flat Four (Puma)
« Reply #38 on: July 06, 2019, 10:47:29 PM »
Thanks Pete, the 0.001" clearance and 2mm pins were what I was thinking would be about right!  Good to have it confirmed....

Chris

Offline Brian Rupnow

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Re: 30cc Flat Four (Puma)
« Reply #39 on: July 07, 2019, 12:05:39 AM »
Loctite has a product that is used with press fits. I see a lot of people on the forums who think that you have to leave some clearance on fits so as not to scrape the Loctite off during assembly. Loctite claims that you don't need to leave any clearance. I don't leave any clearance on fits (not intentionally anyways) and I've not had anything come apart.

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Re: 30cc Flat Four (Puma)
« Reply #40 on: July 09, 2019, 08:05:23 AM »
Conrods done

Before and after zapping in the sand blaster to remove the tooling marks






Time to roll the dice again and decide what to do next

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

Offline Laurentic

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Re: 30cc Flat Four (Puma)
« Reply #41 on: July 09, 2019, 12:25:10 PM »
Interesting comment Brian, must admit I was in the camp that thought a very wee clearance was required before using loctite.  Do you have the loctite number for press fits, I will get some in!   :ThumbsUp:

Nice piston rods Pete.

Chris

Offline Brian Rupnow

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Re: 30cc Flat Four (Puma)
« Reply #42 on: July 09, 2019, 01:35:13 PM »
Top Pick LOCTITE 620 is a high temperature (450 degrees F), high viscosity liquid retaining compound. Provides a shear strength of over 3,800 psi on steel. Locks and secures metal cylindrical assemblies up to 0.015' diametral clearance. Prevents metal fretting and corrosion. Seals against leakage. Recommended for high temperature retaining of parts with a clearance or interference fit, i,e, retaining bushes, bearings, seals, fans and liners. Requires heat cure to achieve temperature resistance. ABS Approved.
This and Loctite 680

Offline Laurentic

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Re: 30cc Flat Four (Puma)
« Reply #43 on: July 09, 2019, 06:07:33 PM »
Thanks Brian, Loctite numbers noted down!!

Chris

Offline doubletop

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Re: 30cc Flat Four (Puma)
« Reply #44 on: July 09, 2019, 08:56:44 PM »
Top Pick LOCTITE 620 is a high temperature (450 degrees F), high viscosity liquid retaining compound. Provides a shear strength of over 3,800 psi on steel. Locks and secures metal cylindrical assemblies up to 0.015' diametral clearance. Prevents metal fretting and corrosion. Seals against leakage. Recommended for high temperature retaining of parts with a clearance or interference fit, i,e, retaining bushes, bearings, seals, fans and liners. Requires heat cure to achieve temperature resistance. ABS Approved.
This and Loctite 680

Agreed

The loco cranks were done with 620 and the Puma with 680

One of the benefits of 620 is the slower cure time so you've got a bit of wiggle room. The job doesn't lock up almost immediately on assembly. It gives you time to get it all together and into any alignment jigs you may be using.

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 #45 on: July 09, 2019, 08:59:49 PM »
Interesting comment Brian, must admit I was in the camp that thought a very wee clearance was required before using loctite.  Do you have the loctite number for press fits, I will get some in!   :ThumbsUp:

Nice piston rods Pete.

Chris

Thanks Chris

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 #46 on: July 15, 2019, 10:22:19 AM »
Well I rolled the dice and, as I had a busy week ahead, decided not to start anything major. So did things like gudgeon pins, cam follower bushes etc. Then the bearings arrived so I was able to do the crank bearing holders.

That allowed a trial fit of the everything I’ve done so far.



This also allowed me to try out the timing belt sprockets. But that led to a bit of a disaster.



Drilling the crank sprocket to fit the 5mm stub on the end of the crank it fell apart (compare to the good one on the left)

Checking the supplier’s catalogue and anything up to 16 teeth is a type 1 on the right are type 2 and they start at 18 teeth. So, it has to be a minimum of 18 teeth on the crank and 36 on the camshafts.

A bit of an update in the CAD and it looks feasible. The order will be placed tonight.



You’ll notice I’ve also included an alternative, simpler, exhaust pipe, the ¼” x 32 spark plugs and a carb sourced from Hobby King.


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 #47 on: July 15, 2019, 10:43:59 AM »

A brief video of the trial fit. No pistons yet so it turns quite freely and the conrods can be heard rattling in the bores


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