The Tailshaft's away - with the Heater Blower I'll play

The tailshaft is out of the Vogue again and with Precision Balancing. The short story is that I have eliminated everything except the tailshaft. I suspect the slip-yoke and front Universal Joint. I'm hoping they can balance the whole lot as a unit.

While I await the return of the tailshaft, I have turned my attention to a noisy heater fan/blower. When I painted the blower and housing I actually didn't quite know how the get it apart fully - I also didn't know if I had a viable spare so I wasn't too choosy. Having found another one under the house, I totally stripped it apart, de-rusted where required, primed and painted it. The bushes in the motor in this one appear to be quite good - not worn and rumbly like the one in the car presently.

I have re-attached the motor in this picture. It's ready to go together again and have the foam fitted to seal the inlet and outlet gaps.

Wedges Installed - Problem persists

I finished installing the two degree wedges on both sides of the car on Sunday afternoon.

This is the front - about 4 to 5mm lift.

This is the rear of the axle perch.

The underside - just 'cause I took the picture.

The differential flange and the motor coupling flange are now within about 0.3 of a degree of each other.

....and the result. Absolutely no change at all!

We even locked the motor speed to 60 km/h to remove any doubt about speed variation and placed a big block of wood under the rear of the motor mount and jacked the car up about 15mm - no change.

I repeated a previous test and jacked under the middle of the motor cradle (the fan end of the motor) - no change in vibration. This stumps me. How can it be that taking so much load on the jack doesn't at least dampen the vibration?

I don't believe I have ever in my life put more effort into a problem with so little return.

So I am faced with a choice now of whether to give up on universal joints and have the tailshaft remade with CVs or persists in trying to find the reason for this vibration. Going the CV route doesn't automatically gaurantee a cure.

Suggestions from mechanically minded folk are very welcome but if you want to comment, please could you read the posts on vibration so we don't revisit older discussions too much (that isn't to say I haven't missed something).

I'm currently trying to ascertain what sized tube wall was used in the new tailshaft.

Ready to Re-assemble Driver Side Spring Mounts

I had wire brushed all the axle/spring mounting hardware a couple of days ago and applied rust converter. I cleaned off the rust converter residue and primed the bits last night. I gave them a coat of gloss black this morning. I can't paint inside the house or in the garage due to overspray, so It's a process of warming up bits (and spray cans) inside, painting the bits outside, then bringing them back in. I guess it doesn't matter much if glossy black bits under the car are slightly dull - but I'd know!

If my hands can keep from seizing up with the cold I'll re-assemble the right hand side tonight.

Changing the Differential Pinion Angle

My spring wedges (sounds like a potato treat with greens), arrived yesterday so last night I set about separating the axle from the leaf spring on one side of the car. I jacked up the car under the diff housing then placed the two rear body jacking points on axle stands. Then I lowered the jack until it was only just supporting the weight of the rear diff/axle.
The U clamps came off pretty easily (with the aid of some CRC56).Once the U clamps were off, I jacked up the axle slightly to removed the top rubber mount.

You can see the leaf spring centre pin that locates the spring on the rubber mounts (next photo).

A slightly blurry picture of the U clamps, upper and lower spring mounts and shiny new two degree wedge.

 

View from the rear of the car.

The spring wedge in the upper insulator/mount. The upper rubber insulators are not in very good condition but I tried unsuccessfully this morning to get new ones. I'll put these back in and keep trying to find a replacement now that I know how easy it is to "drop' the rear axle. I think I'll make a thin wedge to go in that gap in the wedge as well.

The left hand side - still intact. I'm doing one side at a time. That way the "other" side holds everything in place and I don't have to worry that the whole axle will fall out on the floor - tearing the brake lines in the process. The oil stains are an old testimony to (now-replaced) leaking rear oil seals.
I'd love to pull the springs out and clean the whole lot up but I want the Vogue back on the road ASAP. Maybe next year...

A couple of paragraphs from the workshop manual. It's interesting that Mr Rootes sometimes fitted wedges. No, I didn't find any.

Economy Figures for Week-before-last

I forgot to post these. I didn't drive the Vogue last week but the week before with the controller switching at 8kHz and me driving the lowest speed roads I could find for my commute returned some excellent power economy.

Economy figures for the week ending 3rd May 2013:
Monday 9.46 AH for 43.4 km => 131 Wh/km
Tuesday 6.33 AH for 30.77 km => 124 Wh/km
Wednesday 6.55 AH for 30.8 km => 128 Wh/km
Thursday 10.28 AH for 44.9 km =>  138 Wh/km
Friday 6.77 AH for 32.4 km =>  125 Wh/km

As always, all battery to wheel.

Heater Tested and Ready for Re-Installation

Yesterday evening I tested the heater to my satisfaction. I arranged for a temporary control potentiometer and 12 VDC power source for the control board, strapped a blower (funnily enough, the original blower that came out of the donor ceramic heater) to the side of the heater box, placed the whole lot alongside the car and plugged it into the 600 VDC connectors. I "started" the car (engaged traction contactors) and ran the heater for 5 to 7 minutes through a range of heat settings. I then ran it for about 5 minutes at 1.0 Amps - that way I would see immediately if the IGBT ran into trouble as the current would rise to 2 Amps - it didn't.

Another technobabble alert
Just a side note here. During the 12 VDC testing a few days ago, I noted a 1 MHz pulse train at the start of each switch-on pulse - it ran for about 16uS which is significant at the 64uS PWM rate I was running (now 9mS).
Here is a picture of the rubbish at the switch on point measured at the gate drive output. This is with my 9mS PWM rate (110Hz).

I tracked it down to excessively long clip leads going around my test bench causing the switch pulses to get back into the control analogue input. I largely suppressed the effect with a 10nF capacitor across the TL494 voltage op-amp output to -ve input; but it may have been the cause of the IGBT failure. I added the cap. before I realised that it was the leads causing it - but left it in anyway. The input control wires are shielded cable so maybe it wasn't the cause of failure - anyway - worth mentioning.
End technobabble (largely)

Once the test was done I shut it all down, quickly unplugged the 600 VDC connections, lifted the lid (not screwed down yet) and tested the IGBT and various other components for temperature - the finger test. The IGBT heatsink was cool and the only hot components were the two current surge limiters (they are supposed to run hot) - and of course the ceramic element which had already cooled so it was only warm to the touch.

That done I took the box inside and stuck everything that might move firmly in place with the red RTV silicone I've come to know and love.

The heater box is ready to re-install.

Heater Repairs

While I am waiting for my axle/spring wedges to turn up I turned my attention to my non-working heater. I removed the entire cabin unit and extracted the recalcitrant control board. Sure enough the IGBT was a short circuit.

Prior to removing the control board (in the litle grey case). The arrow points at my off-board snubber capacitor.

WARNING - Technobabble alert
I replaced the IGBT, changed the PWM switching frequency from 16 kHz to 110 Hz, placed a 20V Zener accross the IGBT Gate to Emitter and finally moved the 1uF 1200 VDC snubber capacitor to directly onto the PCB. I tested the whole shebang at 12 VDC with a 24W light globe as the load.

All fixed. The snubber is now a power bulge in the gray case (red arrow). I'll RTV silicone it all up when I have tested it with 600 VDC. Note the extra heatshrink where the wires emerge from the control box and generally tidier wiring. The heater wasn't that easy to get out so I don't want to do it again soon.

Driving my thougths to Vibration

While driving the Vogue every day this week, I seldom go for more than a minute without thinkout about my driveline vibration issue. For the time being, I have found ways to and from work that allows me to keep the speed below 55 km/h except for an approximately one kimometer stretch. I can pull in and let traffic go past then keep speed down here as well - usually. Curiously this makes my 25-30 minute commute about 30-35 minutes. Not a substantial difference but no-one likes to travel slowly when they can legally go faster - and it's frustrating because the Vogue's power curve makes it way more fun at higher speeds.

Anyway my thoughts during this drive waver around in the following direction.
Back when I orginally identified that I had a driveline vibration, my first impulse (after tailshaft
balance) was to think that it was caused by the differntial pinion angle. Essentially a Universal jointed
tailshaft will vibrate a lot if the flanges on either end of the drive system are not at the same angle
with respect to the line of the driveshaft.

We thought we had dispelled this theory by temporarily altering the pinion angle using axle stands and a jack, and moved on to removing the motor, dismantling it and having the rotor balanced.
All to no avail - apparently...

Well, looking back I note in the blog (my reference source for all thing EVogue), that at the time
Laurel (wife) thought it improved but "I was looking for a complete cure". It was after that we balanced
the motor's rotor and didn't see any improvement.

What if there are two problems? What if we have fixed one which was masking the other?

My intuition, and elimination of just about everything else, tells me it just HAS to be diff. pinion angle. Add to this that the Vogue originally had this problem before conversion.
A few weeks ago I was put off this theory when told that up to 3 degrees is fine. But in retrospect, the
fella who told me that is a speedway driver. More investigation yields comments like "3 degrees for up to 400 HP, 5 degrees for up to 800 HP". Hmmm. What out normal street travel? I have dug up many references since then that you should strive for under 1 degree difference - preferably 1/2 a degree. This from lowered car folk who run big sound systems and object to their bass being supplemented by driveshaft wobble.

What it boils down to is that you really have to try it.

With that in mind, I have ordered a pair of 2 inch wide, 2 degree wedges from a 4WD online seller in the
USA. They should be here in less than a week.

I'll install them then make the decision of whether to have a new driveshaft made using CVs.
A CV driveshaft will be vibration free but have slightly more loss than a UJ shaft. Changing the pinion angle will help a keep losses lower in a CV driveshaft anyway.

So, watch this spot - or listen subsonically....