Tailshaft with only 1 uni what kind of angle is allowed

[TurboRA28]

Hi all, finally got the driveline handbrake system sorted out in the coasters 1uz conversion..
But.. the front half of the tailshaft that has been designed only has 1 uni on it, where it mates to the gearbox. The other end goes into a drum brake setup that is mounted to the floor on rubber isolators.

So the drum brake section is fixed.. And we have 1x uni on the front shaft.

What kind of angle is going to be acceptable on this uni? Ultimately the gearbox is sitting higher than the fixed drum section, so the front tailshaft will angle down to the drum. Probably a 5cm drop over 50cm or so..
Is this acceptable?

Thanks
Joel

[oldcorollas]

unis don't turn at a constant speed when angled, so the output after 1 uni will speed up and slow down.
can you angle the engine/gearbox down so there is no angle?

5 in 50 is almost 6 degrees (5.7).. which is kinda big?
some places say 3deg is ok but.. there are degrees of ok

can't use a second joint at all? or minimise angle?

[wilbo666]

Unis need a few degrees (1-2? I forget the exact number) of angle, otherwise the rollers don't get to do a full rotation and they wear out quickly was my understanding....

I'd try and set it up with as small as run out that will let the unis roll as possible...

Cheers
Wilbo

[TurboRA28]

I can work on angling the engine down at the back more to reduce the angle.. I don't really want to drop the front of the engine as it'll position the sump below the xmember which I don't really want on this bus as it'll do a bit of gentle off road stuff.

I'd probably be better to try and raise the drum brake.

So if I aim for under 3 deg I should be somewhere in a safe margin.

[oldcorollas]

Unis need a few degrees (1-2? I forget the exact number) of angle, otherwise the rollers don't get to do a full rotation and they wear out quickly was my understanding....

I'd try and set it up with as small as run out that will let the unis roll as possible...

Cheers
Wilbo

thats true, but it is usually assumed that they will have a second uni joint to cancel out the speed differences..

drop the front of engine? it would be raising front no?
so put engine mounts a little higher, and rear crossmember a little lower?

[matty87]

hey mate not an expert on the topic by any strech of the imagination just finishing a mech engineering degree so have a bit to do with this stuff. but any angle on ya shaft with a single uni joint in it will cause some degree of velocity fluctuation causing unwanted vibrations, also there will be the acceleration both positive and negative in each rotation of the uni joint. i did a quick calc and with an angle of 3 degrees and an input shaft rpm of 2000 rpm the out put shaft speed changes between 1997.3 rpm and 2002 rpm in one rotation, if that makes any sense to ya. the shaft also goes through cyclic acceleration with a max accel of 120 radians per second squared ( there are approx 6.14 radians in one rotation) so thats not really negligable. you will also get a fluctuation in the tourque transmission too. This all said you might get away with it but things will wear out faster.

[TurboRA28]

So it really has to be close to straight for this to work...

[Draven]

with 1 uni, you pretty much want 0 degrees. As you get further above this, vibrations are going to increase exponentially (and life of everythign between engine and half-shafts

[oldcorollas]

if it was a 4 cyl, then i guess you could time the elliptical movement of the output, with the engine cycle...
edit: oh.. gearboxes eh?

can you use a rubber donut like in ... whatever big new toyotas i can't remember....
they are for between gearbox and centre bearing, where you don7t wan tto have 2 unis (cost) but don7t want to have solid shaft (so can have a little misalignment)
dunno how it would go with 5-6deg tho,

[matty87]

the use of a second uni at the other end of the shaft set up to cancel out the fluctuations is prolly the best bet. I dont know exactly what the set up you have is but if its possible that would be my game plan. from odd jobs we've done it shouldnt be too hard to get one welded on, saves work changing hights and angles of other things too.

[brett_celicacoupe]

if it was a 4 cyl, then i guess you could time the elliptical movement of the output, with the engine cycle...

he probably wants more then 1 gear




maybe you could use a donut (or pair) from a celsior or aristo.

they are very robust and could easily take a couple degrees of inclination

[oldcorollas]

oh..oops

[TurboRA28]

Ha i actually had one of these as its a celsior engine but we had it machined off as part of this whole handbrake design.. I didn't design any of this, was all designed for us from a shop who had done it before.. but after seeing the finished product im concerned..

[brett_celicacoupe]

yeh i am surprised you didnt keep the donut.

they are a good torsional vibration damper as well

[TurboRA28]

Sorted it all out today, looks like it will be ok. Managed to align it all so there is 1 deg or so on the uni. All very straight.

But twot who did it all got the front and rear tailshaft lengths wrong even after I confirmed with him the measurements like 3 times. So have to wait til next week now and get that corrected.

Thanks all
Joel