Author Topic: 8 cylinder Marchetti Radial Cam Engine  (Read 8205 times)

Offline BillTodd

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8 cylinder Marchetti Radial Cam Engine
« on: March 07, 2015, 06:48:38 PM »


A while ago a guy from the Netherlands asked me for my 3D model of the Marchetti engine so he could make a working model. I've had a few such requests over the years and, although I'm happy to let people have copies, my cad models are for demonstration only so need completely reworking to make a real model.

Wesley has completely reworked the Marchetti model , including figuring out a mathematical formula for the cams (I cheated, and used empirical methods to make my model 'work'), and has designed a compressed air version. :praise2:

He's very kindly allowed me to show you some of the early sketches. I'm sure you will find them interesting.  I'll keep you posted as his model takes shape   :cartwheel:

(He wants me to point out that the pipe work is just 'functional' ATM no doubt he'll come up with something neater later)



« Last Edit: March 07, 2015, 06:55:34 PM by BillTodd »
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Offline Roger B

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Re: 8 cylinder Marchetti Radial Cam Engine
« Reply #1 on: March 07, 2015, 07:05:55 PM »
That's a jolly complicated mechanism  ::)  :headscratch:  I wonder what advantages it was supposed to have over a more conventional design?
Best regards

Roger

Offline BillTodd

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Re: 8 cylinder Marchetti Radial Cam Engine
« Reply #2 on: March 07, 2015, 07:26:24 PM »
That's a jolly complicated mechanism  ::)  :headscratch:  I wonder what advantages it was supposed to have over a more conventional design?

A cam has the advantage of slowing the crank speed for a given firing rate (each piston completes all four strokes in one revolution ) so potentially giving more power while removing the need for a gearbox.  The main problem for this, and the similar Caminez engine, is that the large reciprocating mass verses the relatively low rotating mass of the crank and prop causes a torsional vibration that is/was difficult to control in a light aircraft.

« Last Edit: March 07, 2015, 07:29:38 PM by BillTodd »
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Offline Roger B

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Re: 8 cylinder Marchetti Radial Cam Engine
« Reply #3 on: March 08, 2015, 06:23:31 PM »
Thank you  :ThumbsUp:  :ThumbsUp:
Best regards

Roger

Offline crueby

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Re: 8 cylinder Marchetti Radial Cam Engine
« Reply #4 on: March 09, 2015, 12:37:40 AM »
Thanks for posting those animations! Always fascinating to see 'new' (to me) mechanisms.

Offline swilliams

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Re: 8 cylinder Marchetti Radial Cam Engine
« Reply #5 on: March 09, 2015, 01:12:42 AM »
very interesting

Offline KevinB

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Re: 8 cylinder Marchetti Radial Cam Engine
« Reply #6 on: March 10, 2015, 02:55:05 PM »

That is fantastic!
I love the mechanicalness of it all and how the inner working are exposed.
Will Wesley offer up his model? I would love to have a go at it.

Offline Niels Abildgaard

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Re: 8 cylinder Marchetti Radial Cam Engine
« Reply #7 on: March 22, 2015, 08:31:05 AM »
That's a jolly complicated mechanism  ::)  :headscratch:  I wonder what advantages it was supposed to have over a more conventional design?

A cam has the advantage of slowing the crank speed for a given firing rate (each piston completes all four strokes in one revolution ) so potentially giving more power while removing the need for a gearbox.  The main problem for this, and the similar Caminez engine, is that the large reciprocating mass verses the relatively low rotating mass of the crank and prop causes a torsional vibration that is/was difficult to control in a light aircraft.

According to  CF Taylor The Caminez concept should have died before drawing board.
It ran well on stationary test stand and vibrated test aircraft to pieces .
Aircraft  never rolled under own power.
What should have been done first was to make a torque analysis or simulation and that would have shown that the prop shaft reaction had an enourmeous second order variation and that vibrated test aircraft.
If  made as two row i e 8 cylinder and the  two funny figure 8 things had been skewed 45 degree to each other could have solved this problem.
I think but am not quite sure.
« Last Edit: March 22, 2015, 08:34:37 AM by Niels Abildgaard »

Offline BillTodd

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Re: 8 cylinder Marchetti Radial Cam Engine
« Reply #8 on: March 22, 2015, 02:17:40 PM »
Yes, an eight cylinder at 45 degrees would have helped with the fourth order torque problem :-) 

>Aircraft  never rolled under own power.
Actually the Caminez did fly: (perhaps you mean the marchetti?)

"The Fairchild-Caminez 447 was first flown in an Avro 504 from Farmdale, Long Island, New York, in 1926. It was successfully endurance-tested in 1927, and was the first ever axial engine to receive a US Dept of commerce type certificate. "


To my eye the Marchetti looks to have a greater problem : 8 pistons, conrods, bearings etc. all stopping and starting at one time
« Last Edit: August 27, 2015, 08:48:27 PM by BillTodd »
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Offline Niels Abildgaard

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Re: 8 cylinder Marchetti Radial Cam Engine
« Reply #9 on: March 22, 2015, 03:37:30 PM »

>Aircraft  never rolled under own power.
Actually the Caminez did fly: (perhaps you mean the marchetti?)


I stand corrected.
It is good that I do not give financial or political advice for money.

Offline BillTodd

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Re: 8 cylinder Marchetti Radial Cam Engine update
« Reply #10 on: May 18, 2015, 09:14:42 PM »
Wesley has made some progress.

He's has had the front and rear main plates laser cut and is now working on the cams . This has been an uphill battle for him as he's very new to cnc machining and is learning on-the-job

Here's a picture of the cams :
Bill
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Offline BillTodd

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Re: 8 cylinder Marchetti Radial Cam Engine
« Reply #11 on: July 22, 2015, 11:17:15 PM »
Another update from Wesley:

He's completed the crank frames and one crank assembly and it's all working nicely

He has made a short video of the mechanism here:

http://www.dailymotion.com/video/x2yx565_marchetti-engine-mechanical-principle_tech

Bill
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Offline BillTodd

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Re: 8 cylinder Marchetti Radial Cam Engine
« Reply #12 on: August 27, 2015, 08:45:07 PM »
Another update from Wesley:

He's been having all sorts of problems with the accuracy of his cnc mill. It seems the previous owner was less than careful with it and has damaged an axis in some way (Wesley didn't elaborate) .

With that fixed, he has remade the Cams using his own mathematically derived formula and they look better than ever.

He's making progress with various other parts as you'll see from the photos:
Bill
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Offline BillTodd

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Re: 8 cylinder Marchetti Radial Cam Engine
« Reply #13 on: November 01, 2015, 01:47:53 PM »
The collage summer recess has slowed Wesley's progress, but he is continuing his build.

He has decided to try using Chuck Fellow's automatic exhaust valve idea  (which should same some time and effort compared to making a cam, push rods etc.)

Attached is a picture of his cylinders: he's going to make a working pair (with pistons, valves etc.) as a test prior to making the full set of eight.
Bill
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Offline cfellows

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Re: 8 cylinder Marchetti Radial Cam Engine
« Reply #14 on: November 02, 2015, 05:03:01 PM »
Lovely work on the model.  This is an interesting adaptation of the slave exhaust valve concept.  Sizing the slave valve spring correctly will be important.  In general a weaker spring is best, with a wire size of .010" - .012".  In the past, I've wound my own springs by using a 4-40 or 6-32 socket head cap screw as a mandrel.  With the screw chucked in the lathe at a slow speed, the spring wire will follow the threads for even spacing.  Of course, you need to pick a screw that will yield a spring of the right size.  Also, the ball used for the slave valve should be a loose fit in the exhaust port. 

Chuck
So many projects, so little time...

Offline BillTodd

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Re: 8 cylinder Marchetti Radial Cam Engine
« Reply #15 on: November 02, 2015, 05:44:37 PM »
Thanks Chuck, I'll pass this on to Wesley. i know he reads this forum but i also know he's been distracted by the fantastic offer of a  US scholarship,  so he may miss your .

Bill
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Offline BillTodd

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Re: 8 cylinder Marchetti Radial Cam Engine
« Reply #16 on: January 04, 2016, 09:24:47 PM »
Another update from Wesley...

He is initially making  a pair of cylinders as a test . Here are picture of the cylinder valves , piston etc.
Bill
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Offline BillTodd

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Re: 8 cylinder Marchetti Radial Cam Engine
« Reply #17 on: May 08, 2016, 01:31:33 PM »
Another update.

Wesley has been busy studying but has been making progress , a very fine flywheel has been constructed with thin spokes to allow a minimally restricted view of the cam mechanism...

Well ... it works!  The two cylinder test is a triumph - it really is working well

 http://www.dailymotion.com/Wesley_Tech  (this is ad sponsored so disable any ad blocker or it will hang)
Bill
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Offline BillTodd

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Re: 8 cylinder Marchetti Radial Cam Engine
« Reply #18 on: August 15, 2016, 01:18:14 PM »
More progress:

Wesley has almost completed the other 6 cylinders and started work on the air distribution system and a  stand for the model.

Now he has to master the art of tube bending and how to work with a dead tree !

Plans are afoot for an IC version ....
Bill
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Offline BillTodd

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Re: 8 cylinder Marchetti Radial Cam Engine
« Reply #19 on: October 17, 2016, 08:13:05 PM »
Wesley's progress continues even with the pressure of university work  :NotWorthy:

He's all but finished the other six cylinders and has been working on the peripherals...

Take a look at this stand and weep  - can you believe this is his first time working with wood?  This kid's got real talent  :praise2:

He's even produced a high resolution version of the companies logo for an engraved name plate.

 
Bill
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Offline BillTodd

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Re: 8 cylinder Marchetti Radial Cam Engine
« Reply #20 on: December 12, 2016, 12:14:56 PM »
There was a discussion earlier in the thread about vibration :
Quote from: Bill Todd
To my eye the Marchetti looks to have a greater problem : 8 pistons, conrods, bearings etc. all stopping and starting at one time

Something that Wesley has pointed  out , that had not occurred to me at all,  is that the Marchetti cams move the pistons in a pure sinusoidal motion . 

So it is possible that the Marchetti engine could well have been smoother than one with a crank.

Bill

Yes, an eight cylinder at 45 degrees would have helped with the fourth order torque problem :-) 

>Aircraft  never rolled under own power.
Actually the Caminez did fly: (perhaps you mean the marchetti?)

"The Fairchild-Caminez 447 was first flown in an Avro 504 from Farmdale, Long Island, New York, in 1926. It was successfully endurance-tested in 1927, and was the first ever axial engine to receive a US Dept of commerce type certificate. "


To my eye the Marchetti looks to have a greater problem : 8 pistons, conrods, bearings etc. all stopping and starting at one time
Bill
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Offline Wesley_NL

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Re: 8 cylinder Marchetti Radial Cam Engine
« Reply #21 on: December 18, 2016, 09:00:35 PM »
Hi everyone,

I am the builder of the model Marchetti engine discussed here. Roughly two years ago I got interested in the Marchetti after reading about it on oldmachinepress.com and douglas-self.com. I was eager to experiment with the mechanism and contacted Bill because he made the animation featured on that website. He helped me with information and ideas but also asked me to keep him updated about the progress I made. With it, he kept everyone on this forum informed with the progress.

Since his previous update, more progress has been made. A separate stand is made with an air filter, air lubrication and air flow regulator (see attached picture). The nameplate is finished and of course there are also setbacks, this time with the cylinders. A short time after they were finished (few weeks), a very noticeable corrosion appeared. See the attached picture. I don't know what the precise material is (I got this material from leftovers) but it's not regular brass. I am not yet sure how to prevent this kind of corrosion. My current plan is to use sand paper to remove the marks and then apply a transparent protective layer (wax, varnish or plastic spray). Hopefully that will prevent the corrosion from reappearing in such a short time.

There is more and bigger news:
As of today I have made a website available that is intended to help people learn how to understand and build this specific engine. The main reason for this is that in order to create the cam curves, some interesting but also challenging mathematics are required. I realise that this could be a problem for many model builders. Therefore I have put time and effort into making a website with step by step instructions. All model builders who have basic knowledge with a CAD program should now be able to build a Marchetti engine without having to overcome the maths obstacle. You can visit the website at: http://marchetti-engine.com/

If you have questions, feel free to contact me! I would also love to hear about other possible cam action projects! It is a beautiful mechanism :)


Offline BillTodd

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Re: 8 cylinder Marchetti Radial Cam Engine
« Reply #22 on: December 19, 2016, 04:18:13 PM »
Animation based on Wesley's Cam design
Bill
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Offline Wesley_NL

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Re: 8 cylinder Marchetti Radial Cam Engine
« Reply #23 on: December 19, 2016, 07:09:05 PM »
I'm happy to see that the instructions are useful!

Offline kvom

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Re: 8 cylinder Marchetti Radial Cam Engine
« Reply #24 on: December 19, 2016, 07:26:43 PM »
I downloaded the Solidworks PDF from curiosity.  I'm wondering what you don't also include the SW parts files for download.

Offline gerritv

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Re: 8 cylinder Marchetti Radial Cam Engine
« Reply #25 on: December 19, 2016, 05:35:28 PM »
Bill Long's animation makes it look like a beating heart. Amazing.

Gerrit
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Offline Wesley_NL

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Re: 8 cylinder Marchetti Radial Cam Engine
« Reply #26 on: December 19, 2016, 08:13:23 PM »
I downloaded the Solidworks PDF from curiosity.  I'm wondering what you don't also include the SW parts files for download.

I'm currently a student, if I would start releasing Solidworks models it might backfire due to licence restrictions. I am not willing to take that risk, that's why I put some time and effort into making those instructions as helpful as possible. If you want to build a Marchetti engine, making the cams with perfect geometry is really the hardest part.

Offline Wesley_NL

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Re: 8 cylinder Marchetti Radial Cam Engine
« Reply #27 on: December 31, 2016, 12:23:29 AM »
Progress has been made on the website http://marchetti-engine.com/. The following parts of my work and research are now publicly available:

  • A remake of the historical company logo, available in high resolution and also in dxf format
  • An explanation with all the details on how the mathematical solution of the cams is obtained
  • All details on the method I used to estimate the original dimensions of the engine invented by Paul Marchetti
  • An interactive calculator which visitors can use to calculate their own cam geometry

Feedback and questions are always welcome!

Offline BillTodd

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Re: 8 cylinder Marchetti Radial Cam Engine
« Reply #28 on: December 31, 2016, 02:13:55 AM »
Great stuff Wesley  :NotWorthy:

Lovely animations too 

Interesting analytical derivation, not to difficult follow (but I'm glad you didn't ask me to help with the maths - that's way above my head  :headscratch: )
Bill
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Offline Wesley_NL

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Re: 8 cylinder Marchetti Radial Cam Engine
« Reply #29 on: March 13, 2017, 07:44:44 PM »
Hi all, there's more progress:

An oil reservoir is created for lubricating the engine from the top downwards. The brass tubing on the inside of the engine is also completed and looks quite amazing! The air supply through the wooden stand is finished and the frame + wooden stand are ready to be assembled (see pictures). My next challenge is to create the tubes leading from the engine to the cylinder heads (see figure "Air_distribution_cylinderconnection.jpg". As far as I can see now, this is the last remaining challenge before final assembly.

Also, you can now toy around with the Marchetti engine because the online calculator got a big upgrade:
- You can link to it directly: http://marchetti-engine.com/calculate
- It actually shows each of the wheels rotating, so people who are new to the mechanism can immediately see what's going on
- Hovering your mouse over the graphical area allows you to examine the mechanism at any orientation you like
- You can enlarge it by double-clicking on it (double click again to size it back)
- Enter crazy values, it's really a toy now :)

For those wanting to build their own Marchetti engine: the default parameters are my best estimation of the true historical dimensions. The main website shows the research, elaborating on how exactly those values are obtained. If you want to build the Marchetti engine on a different scale, all you have to do is scale those default values. Then you can export the cam coordinates for your own CAD model (instructions are also on the main website).


Offline 90LX_Notch

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Re: 8 cylinder Marchetti Radial Cam Engine
« Reply #30 on: March 13, 2017, 11:51:33 PM »
Wesley what an unbelievable project.  Fabulous work.

-Bob
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Offline Wesley_NL

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Re: 8 cylinder Marchetti Radial Cam Engine
« Reply #31 on: September 17, 2017, 07:07:40 PM »
I have finished the project but wasn't completely successful in getting it running properly. Even though it did run very smooth on just two cylinders, it absolutely refuses to run on all eight. This is caused by tolerances on the valves (leading to air gaps and jamming parts) and also friction on the rotating points of the arms.

I have decided not to machine all the parts needed to get this engine (first attempt prototype) to function well. Instead I will use the acquired knowledge to design and build a much better one which I am looking forward to!

Offline Admiral_dk

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Re: 8 cylinder Marchetti Radial Cam Engine
« Reply #32 on: September 17, 2017, 07:51:24 PM »
Your engine looks stunning - a shame that it only runs correct on two cylinders - but as you mention, you know how to make a better version two  :ThumbsUp:

Best wishes

Per

Offline ShopShoe

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Re: 8 cylinder Marchetti Radial Cam Engine
« Reply #33 on: September 18, 2017, 01:44:59 PM »
Amazing.

I'm looking forward to the second one running.

I have patience.

ShopShoe