Functioning of transmission
Functioning of transmission
(OP)
I was dealing with one of engine manufacturer and one thing led to another. The manufacturer asked me about bell housing requirement of the engine, which led me to the transmission of the agricultural forklifts. It was not much hard to figure out from transmission manufacturer's site about bell housing requirement. ( JCB - SS640)
Out of curiosity I started getting much into transmission. Couple of things I don't understand about transmission are :
1) How different is Power shift transmission (JCB-PS750) vs Synchromesh Powershuttle transmission(JCB- SS640)? Not just in cabin for
operator, but how its differently built and function?
2) Why transmission manufacturers keep adding more and more speed into gear. I know that driving in last gear is always fuel efficient,
but how its helpful adding more speeds. 4 speed forward vs 6 speed forward, How different it would be in performance?
Out of curiosity I started getting much into transmission. Couple of things I don't understand about transmission are :
1) How different is Power shift transmission (JCB-PS750) vs Synchromesh Powershuttle transmission(JCB- SS640)? Not just in cabin for
operator, but how its differently built and function?
2) Why transmission manufacturers keep adding more and more speed into gear. I know that driving in last gear is always fuel efficient,
but how its helpful adding more speeds. 4 speed forward vs 6 speed forward, How different it would be in performance?





RE: Functioning of transmission
Synchromesh in general implies presence of a 'balk ring' in the dog clutches of a transmission, intended to drag the rotating bits to a common engagement speed during a shift, but the other marketing phrases may be specific to JCB.
2) More gears allow better matching of the engine's torque curve to the load demand.
My 2001 Camaro gets ~31 mpg at 55 mph on level ground in sixth gear (1:2 OD), but it doesn't like climbing hills, accelerating, or cruising slower in that gear. In traffic, I don't use sixth below 80 mph.
Mike Halloran
Pembroke Pines, FL, USA
RE: Functioning of transmission
the reason for more gears is to compensate for the shortcomings of the internal combustion engine. especially in off road use you want to have all the power available at any vehicle speed - whereas the engine can only deliver maximum power at a very high rpm, thus you need to have more gears to be able to match the power requirement to the vehicle speed. take also into account that for example a farm tractor will be used at very different speeds depending on the actual operating activity: ploughing, tillage and transport activities are done with quite different speeds - but may need nonetheless about the same amount of power, and hence the many gears needed to match the engine output to actual requirements.
RE: Functioning of transmission
The answers for second question is pretty much understood but to be honest still confuse about the difference between Power shift Transmission vs Synchromesh Transmission. The one thing I did notice is that in the technical configuration of Transmission, power shuttle is mentioned next to speed "4 Speeds forward / 4 Speeds reverse with Powershuttle".
Even in the case I simply understand power shift vs synchromesh, there is some missing link.
1) http://www.jcbdrivetrainsystems.com/Products/Trans...
2) http://www.jcbdrivetrainsystems.com/Products/Trans...
RE: Functioning of transmission
I don't know the details of the power-shift transmission that you're showing, but it is pretty likely to be a variation of an automotive torque-converter automatic transmission in which hydraulically operated multi-plate friction clutches are used to select each gear and it is possible for them to momentarily "slip" during engagement or disengagement, thus allowing (almost) uninterrupted torque transmission, OR it is a variation of an automotive dual-clutch transmission which uses synchro units to engage each gear but in combination with TWO friction clutches that are capable of momentary slip - and alternating forward gears are connected to each friction clutch (1, 3, 5 on clutch A and 2, 4, 6, R on clutch B or something like that) and a gearchange occurs by pre-engaging the synchro unit on the next gear (no torque transmitted during this process) and then disengaging (let's say) friction clutch A simultaneous with engaging friction clutch B.
RE: Functioning of transmission
RE: Functioning of transmission
Earlier machines used synchromesh gearboxes but had 'shuttle reversers' between the torque converter and gearbox. Also electro-hydraulically activated and utilising planetary gears and clutch packs. It allowed fwd/neutral/rev to be selected by a lever under the steering wheel. A very handy device for machines like front-end loaders, backhoes, etc that required frequent changes in direction.