Augusta progress

[Mikenoangelo]

All that done Karl. Propshaft clean inside , straight and rebalanced (it was not far out). Runs extremely true whether measured in the centre or at the ends. The discs and the locating spiders are new and although I have not spun the new discs as you suggest, they were very accurately made and lined up perfectly with the holes in the driving spiders. The bolts are all the same except one pair which have self locking nuts rsther than split pins, but these are fitted diametrically opposite to one another so that should not be a problem.

The vibration occurs when the engine (and therefore propshaft) reaches 2500 in top gear, but not at the same revs in third. The load does not seem to matter as once started, the vibration continues even when coasting in neutral. I can reproduce all of this with the car on axle stands and it occurs even when run with no wheels or brake drums fitted so not connected with wheel balance, radial or dynamic.

Possibly there is an engine vibration which coincides with some resonant frequency in the transmission and sets the vibration off. It would be interesting to borrow some electronic kit with accelerometers to fix on engine and the back of the gearbox to investigate this. Google does come up with a few ideas.


Mike

[Kari]

I thought you have done that all Mike. Just to let the readers in this forum know how delicate installing a simple thing as a drive shaft with its joints can be.
Some years ago, I had an annoying vibration in the drive shaft of my Augusta too. Running out of ideas, I have changed the commercial sort of 8 mm bolts to close tolerance bolts. That has cured the vibrations, but the only explanation I can think of is, that commerical "8 mm" bolts are often only 7,7 mm or even less. The small differences can add up and cause a flex coupling be out of centre. Perhaps repositioning the shaft by 1/3 turn in relation to the flex coupling and/or the driving spider could help, you might have tried this already.

Karl 

[Mikenoangelo]

You are right about the bolt diameters Karl - generally about 0.2mm less than the nominal size. However the bolts are the original Lancia ones and a good fit to spiders and discs.
I've just found and downloaded a vibration analysis app which uses the vibration sensor of a smart phone and displays the results so I'll have a play with that. Cost under £9.00 my idea is to make contact with the engine etc with a steel rod with a plate on the top for the phone to sit on much as we used to connect ear and motor with a large screwdriver! I have a digital tachometer sensing the ignition so I can set the revs.
Mike

[Raahauge]

I have been following this thread with interest and admiration for the effort put in.
I did not drive my car before I rebuilt it but my car is vibration free using standard commercial M8 bolts in the couplings (replacing a random mixture of different lengths metric and BSF.)
The only thing I attended to in that area was the outer pinion bearing which had excessive end float. I did not measure for any radial play as I had decided to  change it anyway.
If I have read all your observations correctly the problem seems to come back to the propshaft even though it all is balanced and true.
Because centrifugal forces are high I wonder if it is caused by some small amount of play in that pinion bearing, a very small amount would certainly be felt at 2500 rpm. Best wishes.
 

[Mikenoangelo]

The pinion bearings seem to be fine as is the output from the gearbox and no play can be felt. I will drain the axle oil and check for schrapnel but really don't expect anything as it runs quietly with little backlash. What oil do people use?

I've been trying the smartphone vibration app on Sue's Fiesta but was frustrated by a software glitch after a couple of tries. However it did show up a couple  of waves of vibration which corresponded with rpm and half rpm so it does look promising. This was with phone just lying on top of the dashboard.

Mike

[Mikenoangelo]

Lots of investigations done with  the smartphone vibration app which proved to be rather tricky to use, however I did get some useful data which pretty much confirmed my subjective observations on the road. I’ll come back to that shortly.

I refitted the modified shockabsrbers with their Hartford adjustment system and all seems well (photo 169). I had to tweak the arms a little to get precise alignment with the axle brackets and replaced all the rubber bushes with polyurethane. They were easily adjusted on the car by setting the clamping bolts so that the axle would just drop when, with the car supported by the chassis, the jack under the axle was released. On the road they seem to work!

After conversations with Morris Parry and Mike Raahauge I decided that the leaf spring mounts for the engine needed attention. These consist of three leaf spring blades separated by fibre spacers, one end being firmly bolted to the chassis, tightly clamping the spacer and blades, while the other has a preloaded coil spring to clamp the blades and slotted holes in the blades to allow for back and forth movement as the unit flexes. I assume the friction and clamp spring loading together provide a modicum of damping. As the original fibre spacers were extremely mucky and seemed almost stuck to the spring blades I replaced them using woven brake lining material which was available from Saftec. On one of the spring units the blades looked polished when separated whereas on the other they were not, perhaps a sign of malfunction?

The spring units are a bit awkward to dismantle and reassemble as the coil spring is still under compression when the retaining nut is removed. My pillar drill was the answer for dismantling using a large socket to press the ratchet spanner to the nut and control the release of the spring (photo 170).To reassemble I used a short length of tube with the sides cut away so the nut could be engaged with the thread while the spring was compressed (photo 171). Refitting the leaf spring mounts with the engine still in place is tricky, particularly on the driver’s side, working under the steering box but if the left side unit is fitted first, leaving the bolts loose, a jack under the sump allows the right hand unit to be wriggled into place.

Mike

[Mikenoangelo]

Glorious day and no salt so out with the Augusta to see whether renewing the friction pads of the engine bearer leaf springs has done anything. It has - it’s hard to be certain about such things but I do feel that the engine vibration has been reduced and it can now be comfortably taken up to 3500rpm with no major vibrations in the lower gears. I’ve never driven  another Augusta so am really unsure whether the feel of the engine is typical of a V4. It’s not silk smooth! The remaining vibration from 2800rpm upwards in 4th gear is still there and again I could set it off by coasting at speed downhill in neutral.

As I’ve gone through the propshaft and fabric disc U/Js and gearbox and eliminated the wheels as a source I’m wondering whether either the fact that the gearbox has its main through shaft in three pieces rather than two has an effect, or whether the propshaft itself, although balanced and perfectly  straight, could be subject to some form of whirling resonance (like a skipping rope).

I found formulae for calculating the critical speed of the shaft which take into account the length, diameter, wall thickness, properties of steel and bending resistance of such a shaft. Wishing I had paid more attention to maths and physics teachers 70 years ago, I did the sums and lo and behold the critical rpm for the Augusta propshaft is about 2200rpm. This assumes that the shaft is suspended between self aligning bearings. It would be higher if more rigid bearings were involved. Given that the fabric disc U/Js are something between self aligning and rigid, there seems a possibility that the vibration I find at 2800 rpm is down to this cause, possibly initiated or aggravated by the short output shaft through the freewheel compartment.

Of course all the maths involved would have been known to Lancia so it seems unlikely that this form of vibration was inherent in the design. The propshaft itself is a superb item, 1250mm long of 65mm outside diameter and 62mm bore so the wall of the tube is only 1.5mm thick. The whole thing including the three legged driving spiders weighs under 3kg!

So not there yet and more thinking is needed - unless someone else has an idea? A two piece propshaft with an extra bearing and Hardy Spicer U/J in the centre would eliminate whirling vibrations or some kind of vibration damper at the front of the shaft? These would be modifications but if the cause  is a fault, it would be better to cure that. Lancias do seem to be plagued with vibartions.

The first proper drive this year reminded me what a super little car the Augusta is. On winding roads its stability is amazing and although not particularly fast it goes so well for 1200cc of 1936 car.


Mike

[Kari]

Mike,
I like all your postings but especially the last two sentences of your last posting.
Karl

[Mikenoangelo]

 

Mike

[Charles]

I have exactly the same vibrations on my Augusta.  I noticed that my gearbox mounting bush was shagged and so was allowing the gb/engine assembly to rock a degree or two around the axis of the engine mounts. I thought that a very slight imbalance in the shaft might be exciting vibration at the rear of the box because of this slackness. So, rather than drop the box to rebush the mounting I fabricated a cross strut/web with an appropriate bush pressed into it which bolted between the chassis "X" frame just behind the g/box.  I carefully drilled the lug that is conveniently provided underneath the back of the box and bolted it to the bush.  It has stopped the rocking and made the acceleration/deceleration feel more "solid" but, as I half expected, it has not stopped the vibration at 2700 revs in top. So I am currently remounting the flexible coupling using close tolerance M8 bolts but I am now pretty sure that the shaft is slightly bent - about 1mm out of true measured at the centre - and I'm not sure how to proceed.  These things are sent to try us!!

[GG]

Reluctant to offer any thoughts, as you have done so much work already, but here goes. Hope they are useful:

I have been studying Lancia V4s, crankshafts and balancing, analyzing how Lancia addressed balance in the engines.

 So... did these engines vibrate? Yes, they all did - but it was more from being a variation of an in-line 4 than the V. So it shouldn't vibrate more than a 1200cc conventional inline engine - which should be more in the nature of a buzz than a vibration. All the V4s will vibrate, but Lancia went to very interesting lengths to moderate that. The engine mounts are designed to reduce vibrations in two different ways, a composite solution. So the following questions:

Do you feel it in the gearshift lever more than atop the engine?
Consider disconnecting the driveshaft, run the engine and gearbox and see if the vibrations are significant at certain rpm.
Is the crankshaft original, or was it "rebalanced" at some point?
Were the connecting rods changed? Lancia had specific weights for these, but more importantly, lengths. Sometimes people fit new pistons and move the wrist-pin (gudgeon) lower, and shorten the connecting rods. This impacts vibration, surprisingly.
Piston weight changed?

Years ago had a serious vibration issue in an Aurelia, which was almost impossible to get rid of. We finally found that an accident on the front right had shifted the left motor mount a bit, throwing off the axial alignment of the engine:rear transaxle. We only found this out by placing a laser on the crankshaft centerline, and noting when the block was installed, the alignment was 5" off to the side at the rear. Might you be able to check axial alignment coming off the gearbox to the differential? Imagine some large disc, bolted onto the back of the gearbox (minus the driveshaft) with a 90º hole in center, with a small laser.

Check the ancillaries - flywheels and fan especially. Sometimes...

Hope this helps.

Geoff

[Charles]

As you say, 4 cylinder engines (other than boxers) can't be perfectly balanced, hence the use of counter rotating balancer shafts but having said that, the V4 in my Appia is pretty smooth. I'm 99% sure that my problem stems from the propshaft.  Having now refitted the front flexible coupling with close tolerance bolts (not easy because close tolerance means that everything needs to line up perfectly), the vibration at 2700 in 4th gear is noticeably better but not completely gone.  I think that it's time to do a bit of empirical messing around with a jubilee clip on the shaft to see what effect that has in various positions.

[Mikenoangelo]

Charles to answer your suggestions I have run the engine with the propshaft removed both with and without the clutch and gearbox there are vibrations but far less intensive than when the propshaft and axle are connected. I’ve run it in neutral, in top gear and in third with axle and  wheels being driven and the excess vibrations occur at 2700 rpm upward. Using the smartphone vibration app they do coincide with engine rpm and cannot be produced in third gear as the propshaft is then only turning at 2/3 engine speed, 2000 rpm. This corresponds with my experience on the road but I’m not about to try for 4500 rpm in third!

The crank is original and appears to have had one regrind. I doubt it was balanced but am unsure as the engine was rebuilt in Italy by a previous owner. The rods are original but it has been rebored to 71.05mm with new German made Alloylit No 321 pistons which others have found satisfactory. I didn't separate piston from conrod when inspecting the engine but the total weight of piston, rod and bolts was 822 gms. I do not know how heavy the originals would have been.

Its interesting that you also get the vibes at 2700 in the Augusta and in your Appia. My vibration app clearly shows a major peak at 3000 engine rpm which doubt corresponds to the axial rocking frequency of the engine due to the fact the No 1 cylinder is balanced by No3 and No 2 by number 4 rather than 1 with 2 and 3 with 4 as in a normal straight four. It may just be chance that the propshaft resonates at the same revs as can be seen when freewheeling. After playing around with the vibration app I had worked out that the critical speed at which the propshaft would resonate would be 2200 rpm upwards and discussed this with Dunning and Fairbank who had balanced my propshaft. They doubt this, saying that the critical speed for the propshaft would be over 5000rpm so either my maths or my theory are wrong!

Several people have wondered whether the propshaft vibration was the result of some misalignment of the engine, propshaft and axle as you found with the Aurelia with its transaxle arrangement.. I wonder about this as, after all, the propshaft and gearbox/engine alignment is changing all the time on a leaf sprung car as the axle bounces up and down relative to the car so a small lateral misalignment should be easily accommodated by the universal joints.

Anyway I spent a happy afternoon lying on my back under the car checking this alignment. I was surprised and alarmed to find that there is a significant misalignment of the propshaft with the transmission tunnel and other parts of the frame, the tail of propshaft being about 10mm adrift from the centre line towards the right of the car.  This was not what I expected as the car shows no sign of any accident or significant welding, all doors and the boot lid fit perfectly and the back wheels are equidistant from the frame of the car so the axle is not offset. After many more forays with tape measure and callipers I suddenly realised that the pinion shaft is located 10mm to the right (offside) of the centre of the axle so the propshaft must by design, be angled to the right of the car and not perfectly in line with the transmission tunnel. Presumably this allows a smaller offset of the crown wheel from the centre line and therefore a smaller centre section of the axle casing.  So nothing wrong with our car then - phew!

Mike

[Mikenoangelo]

Had another short run today seeking a few steep hills (not hard to find around here!) to wind it up a little in the lower gears. I would say that the engine vibration on the road is now perfectly acceptable up to my self imposed limit of 3500rpm, no matter which gear is engaged so changing the fibre damping pads in the engine bearer leaf springs and freeing the one which seemed stuck has definately made a difference. It is also clear that the vibration of the engine is less under load than when tested with the car raised on axle stands which is understandable.

The vibration which remains must surely be propshaft related - but how? The small built in misalignment of propshaft to car centreline only represents 0.9 degrees so I can't see that having an effect. I assume that having a pair of Hardy Spicer fabric disc universal joints will, like a pair of normal U/Js, result in a reasonable approximation to a constant velocity joint.

Mike

[Mikenoangelo]

I spent much time checking the propshaft finding nothing amiss with dimensions or alignment. I then thought I might find something still out of balance, despite the balancing done when I first got the car, so set it up on two level metal bars on which the bosses of the centering spiders for the fabric U/Js could roll. You have to be careful as of course the three armed couplings are orientated the same way at both ends of the shaft so the shaft naturally rolls so two of the arms are down and one points up. However it does always tend to end its roll with the added balancing weights towards the floor which suggests a problem so I'll try the jubilee clip trick first and then take the shaft back to the company who balanced it.  

Does anyone out there know what this small tag behind the wheel arch in the Augusta boot is for? There are two, one to each side of the boot, obviously to attach a spring or something - but what?