Author Topic: By Jupiter  (Read 32452 times)

Offline Steam Haulage

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Re: By Jupiter
« Reply #360 on: June 07, 2019, 10:52:51 AM »
Mike,

I'm a little confused by your proportion statements. Do you mean that if I build a model at one tenth of full size then the linear measurements of the engine should be reduced by one    third i.e. if the full size stroke of the engine is 200 mm  then the model should be 20 mm - 20/3 mm = 13.33 mm., or something else? And so on with the other dimensions you use.
Could you clarify please?

Jerry
Dogs look up to you, cats look down on you, pigs treat you as equal.

Offline Vixen

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Re: By Jupiter
« Reply #361 on: June 07, 2019, 11:56:17 AM »
Hi Jerry,

My bad.  :embarassed: Perhaps I should have said "divided by 1/3 instead of reduced by 1/3."

I was using my 1/3 scale engine as an example. At 1/3 scale  the linear dimensions of the full size are divided by three. etc etc.

For your 1/10 scale model you should divide the linear dimensions of the full size engine by 10.  Areas would divided by 1/10 x 1/10 = 1/100 and the volumes would be divided by 1/10 x 1/10 x 1/10 = 1/1000.

You can do the similar maths for other scales.

Mike
« Last Edit: June 07, 2019, 12:28:57 PM by Vixen »
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Offline dieselpilot

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Re: By Jupiter
« Reply #362 on: June 07, 2019, 03:36:41 PM »
Reynolds number scales linearly. Models have a hard time with it which is why specialized airfoils for low Reynolds number exist (many developed by modelers).

The difference in wind speed between say a 28" pitch and 40" pitch at 40" diameter is minimal at 1200 RPM. The engine should be capable of 10kW easily, maybe 20kW if the carbs were sized to allow full torque and allowed to rev to 4-5kRPM at the crank. That would make a lot of wind.

Offline Ian S C

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Re: By Jupiter
« Reply #363 on: June 08, 2019, 12:40:50 PM »
One interesting propeller type was used on the 4 engine  Handley Page HP 42 biplane airliner.What appears to be a 4 blade prop is actually two Fairey Reed metal props mounted on the prop shaft at right angles. Doing it this way men't that a spare prop could be transported by air.
Ian S C
« Last Edit: June 08, 2019, 12:47:29 PM by Ian S C »

Offline Vixen

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Re: By Jupiter
« Reply #364 on: June 08, 2019, 03:19:50 PM »
The Handley Page HP42/45, powered by Bristol Jupiter engines, was the mainstay of Imperial Airways during the decade from 1930 to 1940. They provided regular service to all the far fliung corners of the British Empire, including a scheduled route to South Africa and another to India. The passenger traveled in great style, flying at a few thousand feet, at 95 to 100 mph, where they could see every interesting feature; the Nile , the Sphinx and the Pyramids passing by slowly below. A golden era of flight.





Imperial Airways took a very practical approach to their operation, their huge Handley Page biplanes operated for ten years without a single fatality. Using two, two blade propellers mounted back to back, at right angles was their very practical solution to on route maintenance, spare blades could easily be transported to anywhere along the route. I have seen photos of complete replacement engines being attached to the outside of the aircraft, hanging in the open beneath one wing.

They also developed, with Bristols, a unique gas starter to crank over the upper engines, which were impossible to reach from the ground. They used compressed air, mixed with fuel, to blow down each cylinder in turn to start the engines. This was long before electric starters were feasible.

Greg, I will go along with an estimated 20 Kw output from the model Jupiter. My first three cars all had 850cc engines. The 1962 Minii with it's push-rod engine produced 34HP (25Kw) my 1932 MG J2 had an overhead cam but only produced roughly the same power as the Mini, My 1969 Hillman Imp was the star performer at 40 HP (29.5Kw) from it's all alloy / overhead camshaft engine. So 20 Kw from the Jupiter (with a suitable load) seems entirely feasible.

Mike
« Last Edit: June 08, 2019, 04:57:04 PM by Vixen »
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Offline Vixen

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Re: By Jupiter
« Reply #365 on: June 10, 2019, 09:32:14 PM »
Round two in the battle of the 'brown stuff'.

Having cut all the propeller laminations to approximately the right shape, the next job was to glue them together. I ordered a tub of Cascamite Urea-formaldehyde resin, which seemed to take forever to be delivered. The Cascamite powder is mixed with a small amount of water into a creamy consistency. It has a working time of less than an hour, it sets off to handling strength in about 5 hours and achieves full strength in 24 hours.

The Cascamite adhesive was brushed onto both surfaces of each laminate,  to ensure adequate coverage. It is then essential for the laminates to be tightly clamped together during the curing process. The clamps ensure that all excess adhesive is extruded from the joint, to provide the thinnest joint line and the strongest bond. I was amazed at how many clamps were required to close the joint and extrude the excess resin. I quickly used all my G-clamps, my F-clamps, all of my engineers clamps, I even had to use some big vice (mole) grips and both my drill vices.

It may not look very pretty but they did the job perfectly.






I decided that I would carve the flat back face of the blades first before attempting the curved front face. I tried to rough cut the stepped laminations using a brand new course toothed rasp, a curved tooth dreadnaught file/rasp, spokeshave, a plane and various knifes, all to little effect. The Sapele laminations were tough and put up a good fight. I found the only thing which removed the excess wood in quick and controllable manner was the belt sander with a 60 grit sanding belt. I used the curved surface of the front roller, rather than the flat top surface of the belt sander. It was reasonable quick, nice and controllable but very dusty. It's definitely a job which needs to be done outside.

I used the CNC mill to cut a set of metal templates  Each template has the accurate profile for the front and rear face. The templates, numbered A to E, set the height as well as the profile and the correct angle at five defined stations along the each blade.




As you can see, today,we had the first rainfall in months. It may revive the grass, but it meant the hand sanding of the blade profiles had to be completed inside the workshop after all, Not sure how I will ever get rid of all that dust.





It's a slow tedious and very dusty process to finish the blades by hand. I will need to invest is some dust sheets to cover the machines, if this wet weather continues.

Stay tuned

Mike

« Last Edit: June 10, 2019, 09:38:32 PM by Vixen »
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Offline crueby

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Re: By Jupiter
« Reply #366 on: June 11, 2019, 01:16:23 AM »
Looks great so far! The Sapele wood is great stuff, I love it for furniture, looks great, very strong and stable. Watching along with interest ..


 :popcorn:

Offline Art K

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Re: By Jupiter
« Reply #367 on: June 11, 2019, 02:32:57 AM »
Mike,
Glad to see the progress you are making on the Jupiter. I'm not sure but I think you're about a dozen clamps short on gluing that prop. :lolb: I remember an article in Smithsonian air & space I think it was about an Australian airline flew to London and such. They would strap extra engines on outside the plane that they often needed later in the flight rather than a spare later down the road. Scary time to fly if you ask me.
Art
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Online Jasonb

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Re: By Jupiter
« Reply #368 on: June 11, 2019, 07:08:33 AM »
There is a saying "you can never have too many clamps" and even with all mine you can come up short sometimes. Infact at that size I would have popped it in a vacuum bag which does a great job of things like that but you have got to use what you have.


Offline Vixen

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Re: By Jupiter
« Reply #369 on: June 11, 2019, 12:07:20 PM »
There is a saying "you can never have too many clamps" and even with all mine you can come up short sometimes. Infact at that size I would have popped it in a vacuum bag which does a great job of things like that but you have got to use what you have.

Jason, I did think about using a vacuum bag, I still have the vacuum pump from when I did the lost wax castings, but that would have added one more 'unknown' for my journey into the mysterious world of the  'brown stuff'

I remember an article in Smithsonian air & space I think it was about an Australian airline flew to London and such. They would strap extra engines on outside the plane that they often needed later in the flight rather than a spare later down the road. Scary time to fly if you ask me.

Art, Yes a scary time in aviation. Eighty or ninety years ago, "Sex was safe, but flying was bl**dy dangerous"..... How times change.

It seems that many manufactures built in strong points under the wings of the old biplane transports to carry external underslung loads.



This old print shows a Napier Lion 11 under the starboard wing of a Vickers Victoria about to depart 'down route'.

The opening cabin windows must have been a blessing to the embarked troops. They could increase the 'air conditioning' while flying over the hot deserts of the Middle East.

Happier days.

Mike

« Last Edit: June 11, 2019, 07:37:11 PM by Vixen »
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Offline RonGinger

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Re: By Jupiter
« Reply #370 on: June 11, 2019, 06:18:00 PM »
I rode a 747 one night from Tehran to Bangkok. We boarded by walking across the field and climbing up the stairs. The plane had a full engine attached under the wing and up in close to the fuselage. It had a shield over the fan intake of the engine. I talked to the pilot later and found that was common practice to ferry those engines around. They were to big to fit any cargo plane. While flying I noted the small center trim tab of the wing was always slightly above straight, so the autopilot was compensating for the drag.

Offline petertha

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Re: By Jupiter
« Reply #371 on: June 11, 2019, 09:41:45 PM »
Some woodworking glues don't play well with vacuum bagging, but I cant find many links that either strongly support or contradict use with Cascamite types. I suppose better safe than sorry given the ramifications of the important, whirly thing up front. LOL.

On a side note, I remember my introduction to that glue (or varietal) on a FS Sopwith Triplane volunteer project in my teens. When I arrived, the wings & spars were being constructed & it was integral to all kinds of joints & lamination's. I remember trying to break some scrap pieces. The wood always went first, that was some strong sh*t! The prop was largely done when I arrived. Some construction pics they had on a wall looked very similar to yours Mike, with the span-wise stations & templates etc. Stan Green, who headed this project until his passing, was ex-RAF pilot who came to Canada. What a craftsman. He was also an accomplished live steam model engineer which is what first opened my eyes to this particular hobby.

https://www.arcair.com/awa01/601-700/awa680-Sopwith-triplane-Grant/00.shtm
https://www.thehangarmuseum.ca/exhibits/sopwith-triplane

Offline Art K

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Re: By Jupiter
« Reply #372 on: June 12, 2019, 03:45:57 AM »
Mike,
Now I remembered the other thing I was going to mention last night. If you work on the brown stuff in the shop keep it away from the computer that runs the cnc. I can laugh now but it was very unfunny when the computer wouldn't boot up. :lolb:
Art
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Online Ramon

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Re: By Jupiter
« Reply #373 on: June 12, 2019, 10:30:08 PM »
Hi Mike - I've carved a few props over my time as an 'aeromodeller' but never laminated one and certainly not as large as the one you are undertaking. I can imagine just what a beauty that will turn out to be. :ThumbsUp:

I don't know if it is considered the norm in full size but I've always carved the back first to establish the pitch bringing the section true after - looks to me you are well on the right track. As it's relevant I thought you might like to see this as a fine example





It appears to have eighteen veneer thin layers and has a far better finish that the pics convey. It's beauty, in my eyes, is spoilt somewhat by what appears to be silver felt tip pen writing on the blade. I have no idea of the manufacturer - I assume it must be  writing on the blade - 12 inch diameter with a 10 inch pitch I have no idea what the D N stands for though. It was given to me in the last couple of weeks or so - beautifully carved (machined?) and finished  I can't tell you much more than it was intended for use on R/C aerobatic aircraft.  My friend who gave it to me used to fly R/C aerobatics competitively but told me he was always loathe to use it due to it's high cost .

Looking forwards to seeing yours blossom from the blank

regards - Tug
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Offline Ye-Ole Steam Dude

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Re: By Jupiter
« Reply #374 on: June 12, 2019, 11:07:09 PM »
Hello Mike,

I am looking forward to seeing your finished prop.

Have a great day,
Thomas