VW based engines. Pros and cons from users?

[spacesailor]

December  23 2005.

That was the last " flat four air-cooled  "  VW MOTOR PRODUCED. 

In. Sao Paulo Brazil. 

spacesailor

Edited June 28, 2023 by spacesailor
Spelling

[Area-51]

4 hours ago, facthunter said:

The VW has been  in quite a few different versions. ALL flat four aircooled by belt driven fan. Plenty of people killed by  it's heating system. Prone to catching fire when in accidents. Early one's a bad handling thing. Engine behind rear axles and had a suspension where the camber  changed a lot. You loved them or loathed them. Not fuel efficient. Broke crankshafts. Nev

Hillman Imps will forever rule the world 🦹‍♂️

[danny_galaga]

14 hours ago, facthunter said:

The VW has been  in quite a few different versions. ALL flat four aircooled by belt driven fan. Plenty of people killed by  it's heating system. Prone to catching fire when in accidents. Early one's a bad handling thing. Engine behind rear axles and had a suspension where the camber  changed a lot. You loved them or loathed them. Not fuel efficient. Broke crankshafts. Nev

Type 3 had a crank driven turbine instead of belt drive fan. I used to own a notchback. If you broke the fan belt you'd only end up with a flat battery.

[facthunter]

There WAS an industrial  pushrod Porsche engine that was a bit better. Okrasa made roller bearing cranks.   Nev

[spacesailor]

The 1938 VW Beetle type 60 , was designed by '' Ferdinand Porsche " .in 1935 .

So must have been a good design to last that long .

The ' new ' half VW '  MOTOR , can have many refinement's, including :

" Nicasil " ! , ( Nicel Silicon Carbide  ) electroplating . 

with " Electronic ignition " , on two ' spark-plugs '  per head .

which seems good for a " half " 1935 designed motor . 

spacesailor

 

[onetrack]

Well, VW had 70 years to get the design right, Spacey! 

[facthunter]

On some of the VW based offerings there's not a lot of the original motor left. It always LOOKED like an aeroplane motor but the siamesed heads  are not that suited and getting the drive off the crankshaft has always been an issue. It's a Cheap option though for many people over the years when not much else was around.   Brazil continuing to make them gave an extra life to them.  Nev

[Thruster88]

Nowadays one can buy a 2000 hour rotax 912 for less than the cost of a VW + conversion, a better choice.  

[facthunter]

Could depend on whether you want air-cooled and like to do a bit of fiddling. What IF the Rotax has had an unreported prop strike. IF you have to start spending it's large lumps.  There's a real HP differential too.  Nev

[facthunter]

There's 13 separate bits in a 912 crankshaft assembly. That's why I mentioned the prop strike.  I've also seen one prop and part of it's drive come off a VW .  Nothing is perfect.  Nev

[BrendAn]

On 30/06/2023 at 4:00 PM, facthunter said:

Could depend on whether you want air-cooled and like to do a bit of fiddling. What IF the Rotax has had an unreported prop strike. IF you have to start spending it's large lumps.  There's a real HP differential too.  Nev

the  912 has a slipper clutch which protects the crank from prop strike.

Edited July 2, 2023 by BrendAn

[facthunter]

Not really. It's a friction damped cam faced thing that can't fully slip and there's a runout inspection  required.  Nev

[BrendAn]

3 hours ago, facthunter said:

Not really. It's a friction damped cam faced thing that can't fully slip and there's a runout inspection  required.  Nev

yes really. its correct name is an overload clutch and it has a drum and multiple clutch discs. it certainly can fully slip.

[BrendAn]

3 minutes ago, BrendAn said:

yes really. its correct name is an overload clutch and it has a drum and multiple clutch discs. it certainly can fully slip.

[facthunter]

I don't think it should. Its for damping torsional pulses not slipping. One of US is right. They need to be serviced.   Nev

[facthunter]

What do you think those substantial stops are on the end of the splined hub?  Nev

[BrendAn]

51 minutes ago, facthunter said:

I don't think it should. Its for damping torsional pulses not slipping. One of US is right. They need to be serviced.   Nev

The gear reduction units found on the Rotax 912 A , 912 F and 914 F engines incorporate an overload clutch to limit damage in the event of a propeller strike and an axially incorporated torsional load absorber.  this is off the rotax website. i am pretty sure they should know

[facthunter]

 Well it might be there somewhere but must be a very high torsional setting to operate it. I've never heard of one slipping and if it could it would involve risks. I know of no other drive to a prop where this protection is provided.  What's all the clunking going on at low rpm for if it's not cam stops?. Is there a test for the clutch  slip figure that can be done?. If not why not?  Nev

[BrendAn]

30 minutes ago, facthunter said:

 Well it might be there somewhere but must be a very high torsional setting to operate it. I've never heard of one slipping and if it could it would involve risks. I know of no other drive to a prop where this protection is provided.  What's all the clunking going on at low rpm for if it's not cam stops?. Is there a test for the clutch  slip figure that can be done?. If not why not?  Nev

the rotax manual is online nev. look it up and it will explain all.  

the fact that you don't know of any other engine with this feature shows the quality of the 9 series engines.

[facthunter]

Not really. Why does IT NEED it when others don't?  It's costly to make. Why is it there Is it to protect the Crankshaft? It's costly to service. You have to set idle after start revs carefully for smooth warm up and shut down has to be done at slowest revs to avoid nasty shudders. I've flown plenty of hours behind them and you have to teach the finer points to your students too.  Nev

[Area-51]

Everybody is correct on this occasion; but we can still throw mud around the cage because its fun.

 

Heavy Maintenance Section 72-00-00, page 39-54

 

Line Maintenance Section 05-50-00, page 2-10 (propeller strike)

 

Line Maintenance Section 05-50-00, page  15-17 (overload clutch)

 

Line Maintenance Section 12-20-00, page 60-61 (propeller gearbox)

 

The Dog coupling is there to absorb rotational pulsation; it is provided cone  springs to provide a set preload upon the two Dog halves returning the Dog back to central position when the pulsation ends; these Dog teeth are allowed a max limitation of 30deg free rotation at a specified torsional breakaway load. The clatter often heard in a 912 at idle and shut down is from the Dog lugs clashing back and forth due to loss of preload at the cone springs as the Dog ages. They will clatter away until the cows come home and a new Dog installed.

 

The Slipper Clutch is there to absorb sudden extreme torsional loads experienced from propeller strike or kickback when the sprag clutch is damaged. Cone springs are again used within the Slipper Clutch assembly to provide a specified breakaway preload and 360 deg of free rotation at the propeller with the crankshaft locked. Loss of preload can result in partial or in extreme failure total loss of thrust.

Edited July 3, 2023 by Area-51

[danny_galaga]

As the op I just of something that can be a pain with VW, but not sure about Rotax. That is, one of the crank bearings, might be centre, Is a ring rather than two halves. From memory it's so onerous to try and change (the crank is pressed together trapping the ring bearing in place) that virtually no one ever replaces them. So even the fanciest souped up VW might still have it's original ring bearing. I wonder if this is the case for any of the Aero VW jobbies?

[facthunter]

Every VW crank Other than the built up OKRASA roller bearing variant is ONE piece  The  front OR rear bearing(S)  could be round it there's no flange on the crank for the flywheel. Just slide them on and fit the cases on them as they come together The VW has only ONE  bolt to retain the flywheel. The early ones has a case hardened steel crank and the Later ones were Cast SG iron I think and often broke but you could still drive them home if it's close. One person who raced them, changed the cranks every 6 hours. IF you take the prop drive from the pulley end it's only driving on a parallel fitted shaft with one key Nev

[danny_galaga]

Have I misremembered it? I wonder what I was thinking of...

[facthunter]

I don't know Don't worry about it.  I worked on a lot of them at one point in time. Owned 3 and drove one in a rally Probaby one of the worst cars to do it in,,That car broke about  4 cranks and the Chassis. Dead easy car to roll particularly the pre superbug models.. Fitted a crank for one to a  Borgward HANSA as we couldn't buy the real one. None of those cranks have any Counterweighting. ( similar to what most aircraft are).  The shafts look beefy enough but a lot of flat fours broke cranks back then. Even Jowetts.. Nev