John Morrison Posted August 27, 2018 Report Share Posted August 27, 2018 Ian, thanks for the nice comments, and for doing such a grand job of teh crane. Still have the instructions on file in any one wants a set. John. Quote Link to post Share on other sites
joestr6 Posted August 28, 2018 Report Share Posted August 28, 2018 John attempted to send a pm but inbox may be full. Joe Quote Link to post Share on other sites
Ian Vincent Posted August 28, 2018 Report Share Posted August 28, 2018 (edited) Pictures of my gearbox crane. Who can spot the deliberate mistake and no it isn't the missing chain to go round the box, I haven't got a suitable chain in the shed and I will have to pick some up when I am next in a decent hardware store. Rgds Ian Edited August 28, 2018 by Ian Vincent Quote Link to post Share on other sites
John Morrison Posted August 28, 2018 Report Share Posted August 28, 2018 Joe, sorry cleared some space. Let me have an email and I'll ship you the details. John. Quote Link to post Share on other sites
joestr6 Posted August 29, 2018 Report Share Posted August 29, 2018 Instructions received John, thank you very much. Joe Quote Link to post Share on other sites
john.r.davies Posted September 6, 2018 Author Report Share Posted September 6, 2018 Across t'Pond, a similar thread has been started on The Triumph Experience: https://www.triumphexp.com/phorum/read.php?8,1561315 More original and creative ideas there too! John Quote Link to post Share on other sites
Ian Vincent Posted October 21, 2018 Report Share Posted October 21, 2018 (edited) I wanted to check the balance of a flywheel I acquired from Ian Cornish. Not having a lathe or a friend with one near me I measured the diameter of the hole in the centre and it was 23.76mm which is about .05mm less than 15/16". So I bought a 15/16" OD bronze bush with an ID of 3/4" and two oil filled bearings with an OD of 3/4" and an ID of 1/4". I put the bush in the freezer for an hour or so and it was an interference fit in the flywheel and the bearings were also an interference fit in the bush - probably because it was being slightly squeezed. Result, I mounted the flywheel on a 1/4" diameter drill bit and got a consistent reading for where the flywheel was marginally heavy. I suspect that with the clutch pressure plate mounted it will be spot on. Rgds Ian Edited October 21, 2018 by Ian Vincent Quote Link to post Share on other sites
ianc Posted October 21, 2018 Report Share Posted October 21, 2018 This flywheel had been sitting for the last 27 years in a corner of my garage behind a spare engine, and I didn't inspect it before passing it to Ian (via my son and Ian's niece), but I think the small drillings near 12 o'clock and 7 o'clock were made to balance the unit in 1967. As can be seen, the flywheel has been lightened by removing material from the periphery, and originally the clutch was mounted on spacers using Allen bolts. Of course, removing material from the periphery has the greatest effect on the inertia of the unit, and Gordon Birtwistle, test driver for Triumph back then, knew this very well. Ian Cornish Quote Link to post Share on other sites
BlueTR3A-5EKT Posted October 22, 2018 Report Share Posted October 22, 2018 11 hours ago, ianc said: This flywheel had been sitting for the last 27 years in a corner of my garage behind a spare engine, and I didn't inspect it before passing it to Ian (via my son and Ian's niece), but I think the small drillings near 12 o'clock and 7 o'clock were made to balance the unit in 1967. As can be seen, the flywheel has been lightened by removing material from the periphery, and originally the clutch was mounted on spacers using Allen bolts. Of course, removing material from the periphery has the greatest effect on the inertia of the unit, and Gordon Birtwistle, test driver for Triumph back then, knew this very well. Ian Cornish Thank you for the explanation Ian. Quote Link to post Share on other sites
john.r.davies Posted October 22, 2018 Author Report Share Posted October 22, 2018 That's not a lightened flywheel! THIS is a lightened flywheel! Not my own work, but one I've just acquired. It'll be in for next season. Quote Link to post Share on other sites
John Bracher Posted October 22, 2018 Report Share Posted October 22, 2018 Crikey John That's not a ' lightened flywheel', it is a ' li n fl h el' !! Half of the middle is missing!!! Quote Link to post Share on other sites
Peter Cobbold Posted October 22, 2018 Report Share Posted October 22, 2018 11 minutes ago, John Bracher said: Crikey John That's not a ' lightened flywheel', it is a ' li n fl h el' !! Half of the middle is missing!!! - along with half the drivers feet if it explodes... Quote Link to post Share on other sites
john.r.davies Posted October 22, 2018 Author Report Share Posted October 22, 2018 No, this time it's a proper job, C/w Tilton clutch and sintered bronze friction plate. All being balanced with the magazine other bits's as i write. This will spin like a Dervish! John Quote Link to post Share on other sites
Hamish Posted October 22, 2018 Report Share Posted October 22, 2018 This one is mine for the 3a done by the PO in the ‘70’s I think. But it’s still 8.9kg. Quote Link to post Share on other sites
john.r.davies Posted October 22, 2018 Author Report Share Posted October 22, 2018 40 minutes ago, john.r.davies said: No, this time it's a proper job, C/w Tilton clutch and sintered bronze friction plate. All being balanced with the magazine other bits's as i write. This will spin like a Dervish! John "magazine" ?? fat fingers on the tablet I think. That bit of engineering porn weighs in at FIVE kilogrammes, six with the cover. Oh, Boy! J, Quote Link to post Share on other sites
Hamish Posted October 22, 2018 Report Share Posted October 22, 2018 5 minutes ago, john.r.davies said: "magazine" ?? fat fingers on the tablet I think. That bit of engineering porn weighs in at FIVE kilogrammes, six with the cover. Oh, Boy! J, It’ll never tick over with that one then Quote Link to post Share on other sites
BlueTR3A-5EKT Posted October 22, 2018 Report Share Posted October 22, 2018 14 hours ago, john.r.davies said: That's not a lightened flywheel! THIS is a lightened flywheel! Not my own work, but one I've just acquired. It'll be in for next season. Buy an used bullet proof vest and double sided tape it to the tunnel like the drag racing boys do. Peter W Quote Link to post Share on other sites
stuart Posted October 23, 2018 Report Share Posted October 23, 2018 Definite need for a scatter shield! Stuart. Quote Link to post Share on other sites
john.r.davies Posted October 23, 2018 Author Report Share Posted October 23, 2018 You think it's an overlightened flywheel? THIS is an overlightened flywheel! And it's on a Spitfire so potentially will rev more than a 6! Quote Link to post Share on other sites
Waldi Posted October 23, 2018 Report Share Posted October 23, 2018 From a mechanical stress perspective view: with the removal of the material in the slotted holes, the remaining bridges need to absorb all centrifugal forces that the outer (geared) ring exerts on the inner area. So if the remaining area is 25% of the original cross section, the centrifugal (tensile) stresses will be approx. 4 times higher; some additional bending is created as well. This modification in itself may not be impossible, if the original stress levels were low. Smooth contours and large radii help to avoid stress risers. Another aspect is the new expected speed (rpm); if higher than designed for originally, this will further stress the ring. 20% more rpm (like from 5500 to 6600) will result in 41% higher stresses (to the 2nd power with engine speed). From a picture you cannot tell if the stresses (loads) will be too high, a calculation is required for that (at least: I can’t). Sometimes the “grandfather principle” is used: if it has been prooven to work for many years/other applications, it is probably ok. I would certainly make sure this design is prooven design or do the stress analysis. Because if it explodes at high rpm, the bell house is just a cosmetic barrier. Terrible incidents have happened in industry with small steam turbines going in overspeed, often with miltiple fatalities. Regards, Waldi Quote Link to post Share on other sites
Peter Cobbold Posted October 23, 2018 Report Share Posted October 23, 2018 1 hour ago, Waldi said: From a mechanical stress perspective view: with the removal of the material in the slotted holes, the remaining bridges need to absorb all centrifugal forces that the outer (geared) ring exerts on the inner area. So if the remaining area is 25% of the original cross section, the centrifugal (tensile) stresses will be approx. 4 times higher; some additional bending is created as well. This modification in itself may not be impossible, if the original stress levels were low. Smooth contours and large radii help to avoid stress risers. Another aspect is the new expected speed (rpm); if higher than designed for originally, this will further stress the ring. 20% more rpm (like from 5500 to 6600) will result in 41% higher stresses (to the 2nd power with engine speed). From a picture you cannot tell if the stresses (loads) will be too high, a calculation is required for that (at least: I can’t). Sometimes the “grandfather principle” is used: if it has been prooven to work for many years/other applications, it is probably ok. I would certainly make sure this design is prooven design or do the stress analysis. Because if it explodes at high rpm, the bell house is just a cosmetic barrier. Terrible incidents have happened in industry with small steam turbines going in overspeed, often with miltiple fatalities. Regards, Waldi So overall 4 times plus 41% equals almost 6-fold higher tensile stress on the remaining 'spokes'. If John can measure their x-section area at the narrowest point we have an idea of the safety margin, for that particular steel. Peter Quote Link to post Share on other sites
Waldi Posted October 23, 2018 Report Share Posted October 23, 2018 To add a bit: Designs are not always governed by allowable stresses, stiffness (applicable here) or corrosion aspects (not here I think) are some other considerations, but there are more. The load of the clutch is another factor, although probably relatively small. Waldi Quote Link to post Share on other sites
ianc Posted October 23, 2018 Report Share Posted October 23, 2018 The flywheel which Ian Vincent had from me (shown above on this page) weighed about 20lbs (say, 9kg), some 10 lbs less than a standard flywheel, which is similar to Hamish's. Its effect in a road car was certainly noticeable. Would I be happy to drive a car with john.r.davies' lightened flywheel? Having read Stuart and Waldi's comments in particular, I think not, unless the car had a gearbox tunnel made of some extremely strong and thick material. Ian Cornish Quote Link to post Share on other sites
john.r.davies Posted October 23, 2018 Author Report Share Posted October 23, 2018 2 hours ago, Peter Cobbold said: So overall 4 times plus 41% equals almost 6-fold higher tensile stress on the remaining 'spokes'. If John can measure their x-section area at the narrowest point we have an idea of the safety margin, for that particular steel. Peter Thanks, Peter! That datum would be most interesting. It's at the machine shop to be balance with the crank right now. John Quote Link to post Share on other sites
RobH Posted October 23, 2018 Report Share Posted October 23, 2018 That addresses just the quasi-static tensile strength of the spokes which is only half the story. The outer ring is now much less well restrained over much of its periphery and you can picture the unsupported parts between the spokes tending to bow outwards at speed under 'centrifugal force'. Whenever the revs change, this will cause a cyclic stress at each end of the unsupported section where it joins the spoke, which wasn't there with a solid flywheel. There is also a cyclic shear stress on each spoke as it accelerates/decelerates the outer ring when engine speed changes. Cyclic stresses make for metal fatigue...... Quote Link to post Share on other sites
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