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Thread: The Bucket Foundry

  1. #4426
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    Quote Originally Posted by lohring View Post
    The Gnome rotary engine used a piston valve. Of course in a four stroke it had twice the time to function.

    Lohring Miller
    The Gnome rotary was a totally different scenario, - the pistons did not reciprocate, it could be called a pure rotary. - If you study carefully the path of the piston either in a drawing (but better in an animation) it can be seen that the pistons move in a circular motion and the only reversals come in the oscillating conrods (and poppet valves).
    So really the only "reciprocation" which takes place is "relative reciprocation" obtained by the crankshaft axis being offset from the axis of the path of the cylinders/pistons (does that make sense? - hard for someone like me to explain so check an animation). - anyway check at 1:40 in the animation below and it will be clear!

    I guess that i'm trying to say is, that in the case of the radial rotary engines, a valve in the piston crown would not be subjected to the reversals it would be faced with in a normal engine layout - but it would be subjected to centrifugal forces!

    Some (a lot of) guys have done animations claiming they are gnome rotaries when in fact, what they are showing are normal radial engines (with reciprocating pistons) rather than rotary radial engines - they don't seem to understand the different concept!! - the crankshaft should be standing still and the cylinders rotating - could they even be considered 'rotary piston' engines? - or does rotary piston only refer to the piston/cylinder relationship?

    This is a good animation though - I don't understand the language (probably German?) - very good. :-

    https://www.youtube.com/watch?v=zX6ZlYYIsNU
    Strokers Galore!

  2. #4427
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    Quote Originally Posted by Pursang View Post
    The atmospheric valve does work ...but not if you want revs and power, as HD concluded nearly 110 years ago.

    Diameter is one factor. The force available to open it = the valve area X the differential pressure (atmos to inside cyl)

    Counteracting that force is the mass of the valve X the acceleration required to open it in the time available + any spring, if fitted.

    In my calculations for the Supercharged (reverse) uni flow in Oddball I was looking at basic 28mm Titanium 4 stroke valves.
    Force available with 0.5 atmos Boost (and 0 abs. in cylinder) was around 9.25kg

    At 2500 rpm you have 0.006 sec to full open the valve from say 90 atdc to bdc.
    For 7mm valve lift, the acceleration required is 388 m/s2.

    Maximum permissible weight of a valve at 2500 rpm was around 24g, which is almost realistic.

    Unfortunately, the acceleration increases by the inverse of the available time squared.

    At 5000 rpm valve mass must be 6g. At 10,000 rpm = 1.5g.

    Sufficient lift to achieve a decent Intake/scavenge STA plus the rpm limits are a problem.

    Hence Frit's suggestion to make a Christmas wish for Fireproof, pressure-proof, detonation-proof reeds that open at the slightest pressure differential, and with so little mass that they'll allow any rpm...

    The other problem I have with a piston crown valve is that we still have a 'petroil' bottom end and are not eliminating a significant source of HC emissions.

    On the other end...a super/turbocharged reverse uni-flow with a single, do-nut shaped CCC valve in the head

    Real foundry stuff is also coming...

    Cheers anyway! Daryl.
    the limitations of valves to follow cams let alone atmospheric conditions is why F1 uses pneumatics rather than mathmatics
    the hardley engine was a joke on the Valve technology
    Ages ago i posted the ""KOENIGSEGG freevalve



    I would open the valve direct from underneath with a variable length solenoid
    Quote Originally Posted by Katman View Post
    I reminder distinctly .




    Kinky is using a feather. Perverted is using the whole chicken

  3. #4428
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    I understand that the Gnome was a completely different case. It's the only example of a widely used piston valve I could think of. It was still an era when engine design hadn't consolidated around a few concepts. Some really inventive things were tried.

    Lohring Miller

  4. #4429
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    Quote Originally Posted by lohring View Post
    I understand that the Gnome was a completely different case. .......... Some really inventive things were tried.

    Lohring Miller
    Yes, sorry Lohring, - didn't mean to give the impression that I thought you were wrong!, I do realize that I tend to get carried away sometimes, but then, that's me!
    Strokers Galore!

  5. #4430
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    No worries. We old people tend to get crotchety as my great grandmother would say.

    Lohring Miller

  6. #4431
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    Quote Originally Posted by lohring View Post
    No worries. We old people tend to get crotchety as my great grandmother would say.

    Lohring Miller
    Yes, and (certainly in my case) we tend to say the the things we think, when earlier on we knew better or were afraid to say!
    Strokers Galore!

  7. #4432
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    Gedday, hope everyone is still alive….probably sitting at home waiting on someone to post something.

    As we not are in complete lockdown over here (yet), did some 3D printing to make a small pattern. Did a mould in 2 stages and, as before, used the CO2 system. First stage was using 500 gm Superfine grade sand (for 2 of them) for facing the pattern, and when set, topped off with 600 gm of Foundry sand.

    Dunno if these grades are of some international standard, These being our supplier’s grades : -0.300mm, -0.425mm, -0.500mm, superfine, foundry sand. The -0.300 is really fine, might give it a try at a later stage.

    Just gotta put (drill) in downsprue and risers and then splash some metal in, hopefully tomorrow.

    Stay safe fellas.

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    "Success is the ability to go from one failure to another with no loss of enthusiasm.”

  8. #4433
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    Good to see you Ken, keep it going, - I will now be watching with interest as I have a couple of small printers as well - we are in complete lockdown from tomorrow evening - things from now on will be tough and will change forever (as have my plans which were already a compromise! )
    Anyway things are different now and we all need to be in touch! - good luck with the project!
    Strokers Galore!

  9. #4434
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    It's a good time to work on projects. I stopped being a practicing dentist two weeks ago and laid off 5 of my 8 employees then. My office is now run by my younger employees. We are one of the few places where Oregon Health Plan patients can get emergency treatment. So far I've been printing face shields for the office and masks for my wife's adult foster home employees. Everyone is screening with thermometers and disinfecting carefully. Otherwise, the state is locked down as of today.

    Before this all happened, My partner and I decided that the solution to faster model RC boat speeds would be a two speed transmission. Wee need torque to launch the boat and rpm to get speed with available propeller pitches. I'm working on a direct drive and a 1.6 to 1 gear up drive, two speed box. I discovered the ball shift gear box used by Hodaka. It should work well at the low torques we have to deal with. My partner is developing a dog shift version like the F1 gear boxes. We are looking for a clutchless shift at around 18,000 rpm. The planetary gear boxes with band clutches also looked promising, but were much more complex. Also, we can get suitable gears that are used in RC cars for parallel shaft gear boxes. I can make gears if necessary, but commercial, heat treated gears are inexpensive and probably better. We'll see how a 3D printed test version works before I break out my sand casting equipment to cast the case and machine the other internal parts.

    Does anyone have some other two speed transmission ideas? I investigated the RC car gear boxes, bicycicle multispeed hubs, and automatic transmissions but they don't seem to be suitable for various reasons. I also hope to get back to my flat twin project.

    Lohring Miller

  10. #4435
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    Hi Lohring,

    Hi Lohring
    - Times are tough and we need to learn how to live sensibly - really that's how it will remain for people my age! - doesn't mean we have to give up looking for something to keep us happy though!
    That Hodaka gear engagement system was also used by the little Itom 50cc Italian "racers" from the early sixties, also something similar was used in the ISO scooter (from Italy - Milan?- as I found out when I took one apart - impressively well engineered power unit!).
    I feel that Hodaka may have been inspired by those - good idea, but as you say safer for lower torque (relatively flimsy shaft) - In your case (gear up requirement) would it be better to use the output shaft? - anyway, it works at normal revs but I do wonder though how the balls would behave (ie could they be coaxed to retract at all at those very high revs?). Anyway keep us informed. ...... we are about to go into lockdown - worrying!
    Strokers Galore!

  11. #4436
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    Quote Originally Posted by lohring View Post
    It's a good time to work on projects. I stopped being a practicing dentist two weeks ago and laid off 5 of my 8 employees then. My office is now run by my younger employees. We are one of the few places where Oregon Health Plan patients can get emergency treatment. So far I've been printing face shields for the office and masks for my wife's adult foster home employees. Everyone is screening with thermometers and disinfecting carefully. Otherwise, the state is locked down as of today.

    Before this all happened, My partner and I decided that the solution to faster model RC boat speeds would be a two speed transmission. Wee need torque to launch the boat and rpm to get speed with available propeller pitches. I'm working on a direct drive and a 1.6 to 1 gear up drive, two speed box. I discovered the ball shift gear box used by Hodaka. It should work well at the low torques we have to deal with. My partner is developing a dog shift version like the F1 gear boxes. We are looking for a clutchless shift at around 18,000 rpm. The planetary gear boxes with band clutches also looked promising, but were much more complex. Also, we can get suitable gears that are used in RC cars for parallel shaft gear boxes. I can make gears if necessary, but commercial, heat treated gears are inexpensive and probably better. We'll see how a 3D printed test version works before I break out my sand casting equipment to cast the case and machine the other internal parts.

    Does anyone have some other two speed transmission ideas? I investigated the RC car gear boxes, bicycicle multispeed hubs, and automatic transmissions but they don't seem to be suitable for various reasons. I also hope to get back to my flat twin project.

    Lohring Miller
    cvt................
    Quote Originally Posted by Katman View Post
    I reminder distinctly .




    Kinky is using a feather. Perverted is using the whole chicken

  12. #4437
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    Quote Originally Posted by WilDun View Post
    .. it works at normal revs but I do wonder though how the balls would behave (ie could they be coaxed to retract at all at those very high revs?)
    It can be done without balls, as a feller by the name of Jan Thiel demonstrated over half a century ago with his nine-speed Jamathi gearbox, shown here.
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    But strong as that box might be, you wouldn't want to expose it to WOT-shifts too often. And WOT-shifts is what you need to keep a two-stroke on the boil.

    I suppose that there is no need for downshifts once that boat is in the water. And in that case you could use a dog-shift system whereby the dogs have a trailing slope, such that they are automatically pushed out of the way when they threaten to connect first and second gear simultaneously.

  13. #4438
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    The dog-box option is the simpler one. Examples exist, Bewley (UK) and Lenco (US) both did 2 speed boxes for drag bikes.
    I believe the Pro-stock car class still uses a variant of the 4 speed Lenco.

    It's all in the dog shape. They're clutchless full- noise WOT shifts .Usually pneumatic. But you can't decelerate in gear as there's only one load face on the dogs - the other side is cut away.

    I was shown a US made GSX Suzuki drag box recently. The owner can't use it on our local strip as he rides the bike back to the pits rather than decutching and killing the engine.
    I did a full undercutting job on a stock box which is apparently working for him.

  14. #4439
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    Can't comment on gearboxes except to say that Vespas, and I think Lambrettas, had the expanding ball shift (sequential only) mechanism. As Wil pointed out, at 18k rpm, there might be centrifugal issues.

    Splashed some metal today, all went pretty well, but the last one had visible shrinkage, I am pretty sure that the steel baseplate the sand mould sat on was a lot hotter than the first two. It is meant to be a chill. Will do some minor machining tomorrow, prior to the T6 heat treatment.

    Still C19 free..

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    "Success is the ability to go from one failure to another with no loss of enthusiasm.”

  15. #4440
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    Thanks for all the replies. The plan is to start out with the 1:1 ratio then upshift to the higher ratio during the full power run up to the trap. I also worry about centrifugal forces on the balls. I'm glad you think a dog system would work as well. Frits, I don't understand the gear selection system in the gear box you posted. Is there a sliding key that engages the gears? It looks very interesting. I think CVT systems might have too much power loss. We really don't need anything as fancy as that or 9 speed boxes.

    Lohring Miller

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