Pamhard Dyna Junior !
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Thread: Pamhard Dyna Junior !

  1. #1
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    Default Pamhard Dyna Junior !

    Hi
    A reference to this car was posted in the for sales. I was brousing this interesting model, which I would have to say is totally unfamiliar to me. My loss I guess some might say !!
    I was intrigued by some valve arrangement to be seen on the top of the cylinder heads Are these some Panhard secret weapons or what ??
    Jaahn
    https://www.flickr.com/photos/mcphea...57644859041704

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    Theres a neat series of posts ,on panhard dyna here ,do a search ,theres lots of unusual engineering in these cars ,from memory there no valve springs as such but small torsion bars ,used to close the valves ,could be what you are looking at ,pugs

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    1000+ Posts Kim Luck's Avatar
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    I think they might be the Gallic version of "Energy Polarizers".........

    OR;

    Concentric Torsion Bar Valve Springs
    Attached Thumbnails Attached Thumbnails Pamhard Dyna Junior !-1st-type-valvegear350.jpg  
    Last edited by Kim Luck; 3rd November 2014 at 06:42 PM.
    Don't it always seem to go that you don't know what you've got 'til it's gone............

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    Don't it always seem to go that you don't know what you've got 'til it's gone............

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    1000+ Posts gerry freed's Avatar
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    I posted lots of info on the valve system with torsion bars before the crash and some of it still exists on my Panhard threads.
    See the album at
    panhard
    where you can see the hydraulic tappets and the floating rockers.
    The inlet and exhaust valves on each cylinder have a groove in the top in the stem in which collets are fitted locating a forked lever. The lever is splined to the torsion bar. The torsion bar is in two concentric parts - a hollow tube with a rod inside. The two are mated by splines at their remote end. When the pushrod depresses a valve via the rocker it pushes the forked lever which twists the torsion rod/tube. At the far end this in turn twists the concentric part which transmits the force to the forked lever on the other valve. Net result is that when one valve is opened the other one is forced closed and the return force to follow the cam on the open valve is provided by the torsion rod. This set up halves the length of torsion rod needed and has the desdromonic effect of forced opening and closure of the valves by the camshaft.
    There is another twist to it. The rockers float. There is no rocker shaft. The pivot of the rocker is a hemispherical ball and socket. The lateral float of the rocker is limited by brass shims between the push rod end and the sidewalls of the rocker compartment. These are selected on assembly to give a certain tolerance. Above the ball and socket is a cylinder/piston assembly filled with oil that arrives from the low pressure oil system via a concentric passage. In this there is a pressure limiting valve of a ball bearing and calibrated spring. Once the engine starts and pressure build. This holds the pivot down with the right force to remove any tappet clearance and not to interfere with the cross valve forces from the torsion bar. Net result no tappets to adjust and in exchange there are the shims to get right and the installation of the valve, some 3mm in diameter, without the spring and the ball disappearing on the garage floor. Calibration of the spring is also a fiddly affair. The push rods are a low inertia aluminum tube and maladjustment leading to excess resistance will make them collapse. The oil circulation runs at about 5psi, there is no filter and the oil is important for the engine cooling. There are recent modification kits to fit a bigger sump and a filter. Hidden in the oil ways are copper alloy clips that act as non return valves which are important and outside normal expectations of oil systems.

    Unfortunately, this Junior doesn't have its original model engine and is far from faithful in the restoration. I am lucky to have a factory original drawing of the design of the car in 1:9 scale. Originally it had a 38bhp engine which was lifted in the Sprint version to 40 bhp. The much later car, the 24 like mine had more powerful engines and restorers of the Junior are tempted to use one of these. They all use the same engine configuration but a number of approaches were used to lift the power. Because of the way the engines were mounted on a front cradle on their exhaust pipes the engine and transmission floats relative to the body, making a gear selector difficult. One of the signature features was the gear lever on the steering. The later cars like the 24 used a floor mounted assembly with cable linkages, to another classic Panhard concentric assembly to select the gear forks.
    It is a pity that this car lost the original gearchange.
    A good Junior here in France unlikely to fetch more than 20k euros.
    These post war Panhards are fascinating but are far from the engineering practice of the era. I would counsel anyone wanting to own one in Australia to join the DCPL in France and attend the training courses on the engine and gearbox. Otherwise there are a thousand ways to damage these fragile mechanisms by following normal practice. In addition there are a number of special tools required, without which the engine cannot be opened or the valve gear set up, the pistons selected, the crankshaft opened to release the big end bearings, the clearances set up etc. The gearbox is even worse. Don't imagine 2cv experience will help, all they have in common is two cylinders.
    Autocar correctly described these cars as the most expensive economy cars ever created.
    Last edited by gerry freed; 3rd November 2014 at 10:48 PM.
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    Hi Gerry,
    Thanks for that information Very interesting mechanicals. Obviously not designed by bean counters. Lots of work done to get your car to the current condition !
    John.
    PS Kim I thought that the patent referred to something else about valves, not the springs ?? or did I miss something

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    Quote Originally Posted by jaahn View Post
    Hi Gerry,Thanks for that information Very interesting mechanicals. Obviously not designed by bean counters. Lots of work done to get your car to the current condition !John.PS Kim I thought that the patent referred to something else about valves, not the springs ?? or did I miss something
    Jaahn! I thought the patent referred to the concentric valve bit. In the other schematic I posted you can see the parallel torsion bars. The thought of a concentric set of torsion bars is exciting but obviously not the main event, so I believe the "concentric torsion bar valve" system probably had more to do with the patent than what we see in the actual engine. Those funny looking towers above each cylinder did what? We can see the oil supply as per Gerry's images but what were the towers for?
    Don't it always seem to go that you don't know what you've got 'til it's gone............

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    The towers house half the torsion tubes. I will make a short video of the assembly and put it on You Tube shortly at
    YouTube
    Last edited by gerry freed; 5th November 2014 at 12:00 AM.
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    This is the message I get when I click on the link (screen dump in Paint)

    Pamhard Dyna Junior !-private.jpg
    Any day I wake up and don't have to go to work, is a good day
    Every day is a good day

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    When you look in the gearbox you can see the engineer's mind at work. It is designed for minimum weight, volume and inertia of the moving parts. Not a bean counter in sight. Be warned that you can only dissamble and reassemble the box with heat correctly applied to various parts of the cast alu housing.
    To minimise the size of the basic gears he chose a straight through coupling for third. The selector locks the input shaft to the output shaft. Then there are two reduction gears for 1st and 2nd via a secondary shaft using chevron gears where they are directly coupled. 4th is a step up via that shaft. The output shaft ends in a pinion which engages on a hypoid crown wheel. The reduction on that is limited so as to have the smallest crown wheel practical. On its transverse shaft is a conventional reduction gear to the the tranverse shaft which carries the diff and the coupling to the external drive shafts. One piece of genius is the lubrication. The crown wheel shaft has a spiral gear which drives the speedo take-off. It also doubles as an oil pump. It is surrounded by a brass pressed chanmber which expresses the oil pumped by the gear via a short tube into a hole in the centre of the hypoid pinion. Yes the shaft is hollow with radial holes at intervals, so the oil flows back toward the clutch end, spraying the gears and bearings as it goes. It is recovered by some steps in the inside of the housing which cascade it down to the sump via the reverse gear and other moving parts.
    The desgner looked at the forces and their direction at each bearing point and selected ball races and needle races of obscure configuration to manage them. A supurb evaluation of the six degrees of freedom. However, it ended up with needle races internal, external and end thrust discs that were made by a single supplier (Nadia), who have since gone out of business. There is now a standard on needle bearings as on ball races and only one or two that he chose remain in the standard. The synchros are however conventional.
    Repair of the boxes demands special training, special tools, shaped gas burners and an exasperating search for replacement parts. All the clearances are shimmed. The shims are of five different diameters and obviously a range of thicknesses, so you need a library of them before you start. The hypoid aligment requires a special gauge because the point of engagement is hidden in the intricacies of the the casting and has to be measured with a calibrated 90 degree micrometer. One then calculates the shims necessary between the tapered roller bearing behind the pinion and the casting. This bearing is fitted by heating the casting and so a second fine tuning requires further heating and the risk of distortion changing the spacing. Not for the impatient!
    I set up a clean area to recon. several boxes in which I used a lint free synthetic carpet on the dining room table. That worked fine until I set fire to the carpet. The pine table will never be the same again.
    Last edited by gerry freed; 5th November 2014 at 12:43 AM.
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    Quote Originally Posted by FIVEDOOR View Post
    This is the message I get when I click on the link (screen dump in Paint)

    Click image for larger version. 

Name:	Private.jpg 
Views:	304 
Size:	78.3 KB 
ID:	62616
    It is still uploading and says it needs another 39minutes!
    It is now up and running!!!
    Last edited by gerry freed; 5th November 2014 at 01:49 AM.
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    Should you wish to work inside an engine you need to remove the rear cover plate which is usually cemented to the block by gasket varnish on its metal to metal fit. Not easy as there are no spots for inserting a lifter without risking damage to the alloy block. A paint brushing of paint stripper or acetone and a couple of hours usually helps. You can't open the front of the motor without removing the cam shaft drive gears. They are chevrons and so have to slide off the shafts together. One is retained by being pressed in place and a conventional extractor won't fit. There is a special tool which engages in an inner grooves of the camshaft gear. It is extacted by a screw working against the end of the shaft. With care an alternative can be made with washers cut in two and retained by smaller washers on a bolt with lock nuts. The cylinders can be removed with a special spanner that fits between the retaining bolts and the head castings. Once removed you need a wooden fork to retain the piston otherwise rotating the crankshaft will break the piston skirt on the block.
    Pistons are a selective fit and there is an arcane way of selecting them. You first machine and hone the cylinder to a good wear free finish. It is a steel liner pressed in the alloy head. Acess to the valves is Bugatti style and the combustion chamber is not removable. Then you take a selection of the pistons marked by letter A though somewhere around M if I remember rightly. You mount the cylinder vertically on the bench. Without rings and with oil free surfaces you drop a piston in the cylinder. If it falls immediately it is too small. If it sticks it to large. Somewhere between the two a pston will drop cushioned by the air flow in a few seconds. That is the one to choose. Next you need a precision balance to weigh the pair. there is a small lug inside the piston that can be ground to match the weights. Next you have to balance the combustion chamberr volumes. On a partially assembled engine with the plugs removed, using a burette you fill the combusion chambers in turn with oil. The difference in volume has to be corrected by grinding the head as the pistons are balanced for weight. If you skip any of these steps this highly tuned two pot will run rough and if pressed hard burn out or seize a pot.
    The crankshaft can be serviced but is well beyond my scope and needs special tools. The conrods have narrow big ends of large diameter in which are fitted patented two tier roller bearings. These are pressed in place between the two crankshaft ends, there being no split bearing shells. The one specialist for recon of crankshafts charges about 1000 euros for the service. By designing them this way they have minimised the offset between the cylinders and hence the engine imbalance. It follows radial aircraft engine practice.

    The sump is cast in the block and the internals are accessed through an inspection plate which reveals the oil pump. This is spiral geared to the camshaft. The secondary gear drives a vertical quill shaft which ends up driving the distributor and fuel pump. One that shaft is another unexpected feature. It widens out to be rotating valve. This fits in betwwen a plenum chamber and the crankcase. As the pistons move in and out together they create pulses of vacuum and pressure in the crankcase. The valve is synchronised to capture the low pressure and store it in the plenum chamber. Why? Because the gearbox was made without modern shaft seals and to keep the oil in they have it sealed and connected to this low pressure reserve. It sucks it back in and there is a venturi in the tube connecting them which is set up to give the right airflow and to stop the oil climbing back into the engine!
    The timing of the distributor and this valve is set with a special gauge as it is done with the engine open by selecting the gear teeth on the oil pump and the spiral camshaft gear (odd numbered teeth again).
    I could go on and on with this nightmare inducing bedtime story.
    Last edited by gerry freed; 5th November 2014 at 02:16 AM.
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    And I thought setting the cam timing on the old Porsche 356 quad cam engines was a nightmare. At least that is just a matter of carefully setting spiral bevel gears up.

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    Default Hmmmm very interesting :)

    Hi Gerry
    Thanks for the video. Did that make it clear !! Very clear thanks, perfect, I see it all now. The "thing" is just the 'cover' for the top half of torsion bars. More useful than 'Energy Polarizers', that's for sure

    I have a Honda Cl (CB)450 with torsion bar springs, no prize for guessing where some of its ideas came from Not as complicated as the Panhard never the less. Honda never made another model with them either.

    I just love those vernier arrangements where the spline numbers are different at each end and the angular setting can be small. With 4 ends the possibilities are even greater, if you have the time to set it up

    Kim,
    I see the first diagram with the parallel torsion bars, is labeled "first type valve gear". I guess Gerry's is the second or later type ?
    I tried to read that patent to understand the operation but it was hard going however I think I understood it after the last summary. Patents are usually like that I have found. Not sure why they thought it was a great idea though It never took off that's for sure.

    Cheers and thanks all for the technical journey, I enjoyed that.
    John
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    1000+ Posts Kim Luck's Avatar
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    Quote Originally Posted by gerry freed View Post
    The towers house half the torsion tubes. I will make a short video of the assembly and put it on You Tube shortly atYouTube
    Thanks for the video Gerry! It explains the concentric system nicely. Obviously the parallel torsion bar set-up wasn't complicated enough for the fifty's!
    Don't it always seem to go that you don't know what you've got 'til it's gone............

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