jaime66 Posted October 3, 2021 Report Posted October 3, 2021 Been to see a boat with Kelvin J3 engine and it has wheel for throttle plus a wheel for gear change is there any reason for a wheel for gear change over a push pull set up ?
MtB Posted October 3, 2021 Report Posted October 3, 2021 Yes. The gear change on the reversing gear is a Reynolds chain gearwheel around the output driveshaft, which needs rotating approx two whole revolutions to go from fully ahead to fully astern. If you can easily devize a push-pull mechanism to do this, you're a better man than most boatyard engineers!
agg221 Posted October 3, 2021 Report Posted October 3, 2021 24 minutes ago, MtB said: Yes. The gear change on the reversing gear is a Reynolds chain gearwheel around the output driveshaft, which needs rotating approx two whole revolutions to go from fully ahead to fully astern. If you can easily devize a push-pull mechanism to do this, you're a better man than most boatyard engineers! Other than take off the gearbox and replace it with a hydraulic drive you mean...! Alec
jaime66 Posted October 3, 2021 Author Report Posted October 3, 2021 Cheers for feed back sure if we get boat we will get use to it !
BEngo Posted October 3, 2021 Report Posted October 3, 2021 Before you buy, inquire if the gearbox has lined clutches or metal to metal ones. The former are fine. The latter can be a right b@st@rd to get out of gear after a spell in ahead gear. It can be disconcerting to approach a lock or swing bridge and find that there is no elegant way to stop quickly. N
jaime66 Posted October 3, 2021 Author Report Posted October 3, 2021 Will do , engine has been rebuilt and serviced by Dick Goble I believe so well looked after
MtB Posted October 3, 2021 Report Posted October 3, 2021 33 minutes ago, agg221 said: Other than take off the gearbox and replace it with a hydraulic drive you mean...! Alec True, I have a Velvetdrive on the back of my K2! Still have a vestigial wheel to control it though
BEngo Posted October 4, 2021 Report Posted October 4, 2021 15 hours ago, MtB said: If you can easily devize a push-pull mechanism to do this, you're a better man than most boatyard engineers! The principle would be fairly simple: a suitably high helix angle nut driven by a matching threaded rod which in turn rotates a chain wheel. Something like the insides of a Hatton paddle gear. Pull and push the rod rotates the nut. A Bugger to make without some fairly specialist kit, though one might possibly be able to adapt a worm type steering box from an elderly vehicle. An alternative would be a rack and pinion, but that would give you the problem of changing the plane of rotation between the pinion and the Kelvin gearbox. Bevel gears would be needed. OTOH, the gear wheel is easy to get used to, and it will teach you to manoeuvre gently and to think ahead. It certainly is not as quick to use as a push pull set up. N
Jen-in-Wellies Posted October 4, 2021 Report Posted October 4, 2021 3 minutes ago, BEngo said: a suitably high helix angle nut driven by a matching threaded rod which in turn rotates a chain wheel. Something like the insides of a Hatton paddle gear. Wear a blue shirt and a life jacket when you liberate the Hatton paddle gear internals. Put a yellow CaRT sack over the remains when you leave. The perfect crime. 😀
agg221 Posted October 4, 2021 Report Posted October 4, 2021 Oates has a J2 with a hydraulic drive. We took it off the Trent on Saturday, on to the T&M which was our first real outing with it. The rod hydraulic drive transition works very well - to the point where stopping was surprisingly quick even allowing for letting the engine revs drop. It doesn't half shift in reverse too! The wheel geared approach would require a bit more planning and thinking but I don't think it would take long to get used to. Alec
David Mack Posted October 4, 2021 Report Posted October 4, 2021 Wheel gear change was standard on all the Grand Union boats built with Russell Newbery and National engines fitted with a Brunton's gearbox. Many of those boats still have it fitted, whether still connected to a Brunton box or adapted to control other models. It's not hard to use, and as BEngo says, teaches you to think in advance about your manoeuvring. Just because you can bang a lever or rod operated box straight from forward to astern doesn't mean you should!
billh Posted October 4, 2021 Report Posted October 4, 2021 The wheel change means you don't run the risk of knocking the Chief Engineer/ERA out with the push pull system😀. Wheel is more positive with less slack than the various linkages and levers
ditchcrawler Posted October 4, 2021 Report Posted October 4, 2021 6 hours ago, BEngo said: The principle would be fairly simple: a suitably high helix angle nut driven by a matching threaded rod which in turn rotates a chain wheel. Something like the insides of a Hatton paddle gear. Pull and push the rod rotates the nut. I thought the idea of a worm drive was to prevent the worm turning the nut which is why vices and bolts work
dave moore Posted October 4, 2021 Report Posted October 4, 2021 I ran a J3 in my old boat for almost 20 years. Lovely motor, the measured triplet on tick over was delightful. The gear change was by wheel, never a problem. The engineer who fitted it preferred it to the Gardners he usually installed.
BEngo Posted October 5, 2021 Report Posted October 5, 2021 14 hours ago, ditchcrawler said: I thought the idea of a worm drive was to prevent the worm turning the nut which is why vices and bolts work It usually is, hence why I said "a suitably high helix angle", and why it is hard to make. Hatton paddles are one example where the weight of the paddle and threaded rod drives the nut whist the paddle is self-closing. Early motor cars also had worm and wheel drive to their back axles and they have a suitable high helix angle worm/wheel to allow the inertia of the vehicle to drive the shaft on overrun. Otherwise the back wheels would stop every time the throttle was closed. N
MtB Posted October 5, 2021 Report Posted October 5, 2021 3 hours ago, BEngo said: It usually is, hence why I said "a suitably high helix angle", and why it is hard to make. Hatton paddles are one example where the weight of the paddle and threaded rod drives the nut whist the paddle is self-closing. Early motor cars also had worm and wheel drive to their back axles and they have a suitable high helix angle worm/wheel to allow the inertia of the vehicle to drive the shaft on overrun. Otherwise the back wheels would stop every time the throttle was closed. N As would the engine, unless the clutch was depressed too!!
agg221 Posted October 5, 2021 Report Posted October 5, 2021 3 hours ago, BEngo said: It usually is, hence why I said "a suitably high helix angle", and why it is hard to make. Hatton paddles are one example where the weight of the paddle and threaded rod drives the nut whist the paddle is self-closing. Early motor cars also had worm and wheel drive to their back axles and they have a suitable high helix angle worm/wheel to allow the inertia of the vehicle to drive the shaft on overrun. Otherwise the back wheels would stop every time the throttle was closed. N The long helix should work, but you may need a rather long throw on the rod. The longest I have encountered on a rod was about 2' from full forward to full reverse, which was quite tricky to feel for inside the cabin roof when wanting to reverse. I think if I was trying to do this, I would go for either rack and pinion or a con-rod onto a wheel, the latter needing to be put round a 4:1 ratio to gear it up for two full turns. I would also be inclined to look at pulleys and v-belts to take the rotation down from the control rod to the engine as they the half twist could be introduced directly without any gearing. In practice, I would leave it as wheel and wheel! Alec
MtB Posted October 5, 2021 Report Posted October 5, 2021 43 minutes ago, dave moore said: Wheel and wheel for me too. I have a wheel for forward/reverse, and a lever for the engine speed on mine...
dave moore Posted October 5, 2021 Report Posted October 5, 2021 First lever throttle I’ve come across, no reason why it wouldn’t work. Maybe a wheel with the right gearing might be more sensitive?
Victor Vectis Posted October 5, 2021 Report Posted October 5, 2021 On 04/10/2021 at 11:25, Jen-in-Wellies said: Wear a blue shirt and a life jacket when you liberate the Hatton paddle gear internals. < snip > I was wearing a blue T-shirt and a life jacket when I came down Hatton last month. Got mistaken for a locksmurf.........twice!
Mad Harold Posted October 5, 2021 Report Posted October 5, 2021 50 minutes ago, Victor Vectis said: I was wearing a blue T-shirt and a life jacket when I came down Hatton last month. Got mistaken for a locksmurf.........twice! You must have been drinking a mug of tea and looking gormless. 😄
tom_c Posted October 5, 2021 Report Posted October 5, 2021 I have a push pull gear change operating the standard Kelvin gear change through a series of pulleys, wire rope and chains
jaime66 Posted October 10, 2021 Author Report Posted October 10, 2021 So wheel and wheel it is then ! cant bloody wait !!!!
MtB Posted October 10, 2021 Report Posted October 10, 2021 (edited) 1 hour ago, jaime66 said: So wheel and wheel it is then ! cant bloody wait !!!! Yes, it really is no trouble at all. So you're getting a J3 then?! Congratulations, I'm well jealous!!!! 👍 Edited October 10, 2021 by MtB
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