Derrick the Volvo! Update P47

[macplaxton]

he wouldn't warranty the prop without the slider, as UJ's aren't meant to take forces in that direction.

Ok, I'm not saying nothing moves when I say fixed, but just starting from that consideration. Now I still don't see the point in using a slider on a prop that may move minimally, I'd use something rubber. Hell, if you have to change a rubber coupling of some sort every now and then, I don't see that being a big deal, providing it is easy to change (which on a standard prop isn't).

Any idea what the weight difference is between a bog standard and the custom prop? Must be some inertia in a steel prop. Two-way street as well, heavy acceleration will wind its way back to the rear, heavy braking will wind its way forwards to the engine.

I remember seeing a twisted prop once too. Bookmarked it somewhere.

When you find it....bung it up. I thought I seen one too, but I could be going mad here.

I'm sure the reason the box failed is because the engine is able to move, however the gear box is not, at least not enough

Brings us back round to why Volvo amongst others have resorted to a torque tube on this layout.

Shock damping I'm in two minds about, in theory, isn't that what the clutch springs (in the friction plate, not the pressure plate fingers) should be doing?!

They only take up the shock during clutch engagment outside of that window, the clutch springs do nowt. Say you're at the bottom of the hill in second gear and floor it...they wee springs aren't doing bugger all.

[jon-ovlov]

Hmm, yeah. Damping wise a rubber donut around the splines like a standard one, but locate it on the ends of my prop, giving damping. if these fatigue over time, they would be easily replaced.

Weight difference I can't say exactly, but it is significant. I'd say 2.5 times the weight of the standard prop. The weight didn't help in the failure of the casing that's for sure! If there was a central support, like the torque tube, there would most likely be no problems.

Here's the link of the failed prop. His standard prop shattered the casing at the same point though, so it gets rid of the theory of the extra weight, but re-enforces the theory of miss-aligned engine mounts. Scroll down a little and you'll see it.

http://www.streetrace.co.uk/forum/showt ... hp?t=26012

For all I know, the box could have been fatigued already a small bit, and the new prop has exacerbated the situation. Though, that is very unlikely.

[volvodspec]

besides the massive torque of a redblock wich would allready greatly reduce the lifespan of a prop,
redblocks were usually supported with one mount on either side of the engine, and a mount at the gearbox. 3 mounts to hold the engine/box in place.
hangin a engine on just 2 mounts with a flexible prop to link to the gearbox would make the engine dance all over the place wich would again reduce the lifespan of a prop.

with 300 and the conventional M45/M47 gearbox not being able to fit behind the engine but at the back, a simple lengthened "adapter" was all they need to space the gearbox away from the engine. because the engine torque can move the engine a bit; the wide gearbox mounts as with the 340 would be too stiff due to the radial arm from center of gearbox to the mount; that's why the torquetube got it's gearbox mounts right next to the box and with quite soft dampers.

give the "adapter" a fancy name and tadaa, torque tube was born. advantages like perfect weight distribution of the car were a nice bonus, 300's were never ment as high power racemonsters; even 360. if it would they would've made the redblock turbo engines available. that would make the car simply too expensive for the public it was designed/ment for.

why 300's got a torquetube is simply because altering the shell/floorpan and creating mounts for a clocked rear axle was a way more expensive undertaking that next to the 340's shells would become a big problem in Born in terms of stocking up parts (think about it, even dashboard, floormat, heater, gearbox itself and rear axle assembly etc would have been completely different and you get a double stockpile of different parts at the factory warehouses)

[macplaxton]

That's the pics I remember seeing! Cheers

Statically the weight of the prop, has to hold itself up and the front and rear splined shafts have to hold it up too. Dynamically, all that weight can't be good, even if properly aligned/balanced, as things don't necessarily stay in perfect alignment and everything shoogles about a wee bit.

A single donut of some design might be sufficent at either end, rather than two.

why 300's got a torquetube is simply because altering the shell/floorpan...

Ok, yes it was, but why on other front engine / rear gearbox designs do they do it? Is it because everything moves about too much if there isn't something solid between the pair?? Is there another way of achieving the same result?

[Ovlov 3.6L]

All very interesting information about your propshaft problems.

For the last years I also had problems with the standard prop-shafts. (In my 343 with a 1.7 turbo B18FT engine)
It was the vulcanized rubberwhich caused the problems. I never had problems with the splines because problems with te splines mostly are caused by a not-tight-enough-clamb.

I asked several company's to build an propshaft which can handle 7000rpm and 350Nm of torque. By their opinion, it is allmost impossible to create a prop-shaft without any vibrations with this length, which has to handle such amount of torque and a maximum rpm of 7000 out of steel......... The best solution, they said , is making a doublem propshaft. So I did:



Begun with a propshaft of a Volvo 244



Made it shorter



Dismantled the splines bushings



Made it shorter



Only needed a flange



So let it be made by a collegue of mine



Welded the spines bushing in the flange



Need to drill the holes



Shortened the propshaft en putted in the original joints and welded it myself



And its ready to mount under the car



Voilá!

In the beginning I experienced some problems with some slight vibrations. So I balanced the propshaft myself and the biggest vibrations are gone. Now I'm wating to test it a full day on a circuit

[macplaxton]

it is almost impossible to create a prop-shaft without any vibrations with this length, which has to handle such amount of torque and a maximum rpm of 7000 out of steel......... The best solution, they said , is making a doublem propshaft.

Interesting. I knew that the wheelbase of the car and the length of the standard prop supposedly had something to do with it being about the limt before a two-piece prop would have been required. Must be something to do with harmonics and building a prop where the vibration occurs outside the speed range it is run at or something (I'll stop there as I'm starting to offer technical advice of a poor standard here )

[Chris_C]

For the last years I also had problems with the standard prop-shafts. (In my 343 with a 1.7 turbo B18FT engine)
It was the vulcanized rubberwhich caused the problems. I never had problems with the splines because problems with te splines mostly are caused by a not-tight-enough-clamb.

Hey Ovlov, why do you think your rubber was breaking? Was it shearing at the bond, or in the middle of the rubber?

Only I found all these problems with my F7R (I'm glad I've not got to worry about my B18FT yet... hopefully get all the problems fixed on one car before starting to worry about the other!)

http://www.volvo300mania.com/forum-uk/v ... &start=360 have a read of that topic, around about there and forwards for 3 or so pages. Mine was soley down to the engine mounts not holding the drivetrain in line enough.

[jon-ovlov]

Anjo, that makes sense. It's a lot easier to use space available instead of re-designing the whole car. I also thought about the gearbox mounts. The box pretty much has no movement available, so instead of the mounts flexing to compensate, the casing cracked.

Ovlov 3.6L, very nice work on the prop. It's an option, and adds some much needed support when going for a heavier prop. The Nissan S13s etc have a 2piece prop, so it might be a better option, we'll see.

Thinking of weight, I had a talk with the prop company that built my prop. Apparently fluid in the prop wouldn't affect balancing? I'm not convinced by that. Balance it once, ok. Then when you restart spinning the prop, the liquid will spin possibly in a different area of the prop, affecting the balancing. Surely? I also started talking about the weight of the prop compared to the standard one, and another chap who worked there who is in charge of balancing said "why do you need the slider? It's bloomin' heavy and is only needed really to compensate for change in suspension length". FFS. To which I answered "I discussed this with the guy who built it. I did say I don't necessarily need the slider, as the box doesn't move, and neither does the engine forwards and backwards. But he wouldn't warranty it without one" Unfortunately the man in question who built it is ill today' I'll discuss it more with him when he's in. So my thinking is I will get the slider removed, and get refunded the price it cost for the slider. I'll be damned if I'm going to get no refund because of something that will be removed and wasn't actually needed. It was a significant chunk of the price too. Another thing was that they didn't balance the prop with the couplings at the end. But as soon as the couplings are bolted to the shaft, they become part of the shaft, so they need to be balanced with the rest it, including bolts and clamps. Surely this is right. If something is spinning at high rpm, it needs to be balanced somehow.

Overall, if it was balanced properly, there wouldn't have been a problem. Even with the weight, a significant part of the weight was the slider, which at the time was at the engine end of the car, not the gearbox end.

[Chris_C]

I'd go a slightly different way and have the couplings balanced separately.

It's like production vs race engines, race will balance a matched crank, flywheel and clutch so the unit is perfect (and no one part can then ever be rotated...) where as a production line balance each component, so you can use any part in any orientation (i.e. a bucket of cranks, a bucket of flywheels and you don't have to pick out the correct ones).

If you have them balanced as a unit, you HAVE to ensure you always get the correct bolt hole on the coupling lined up with the correct bolt hole on the prop. Just seems like a hassle not needed.

[jon-ovlov]

I marked the couplings slider and solid, so I knew which one goes on which end, and marked them accordingly, so I know which way they will go when bolted up. (sorry, forgot to say). I did tell them to balance them with prop. If they don't bother, I'll get someone else to balance the couplings on there own, just for piece of mind. Just so I can eliminate all the possible areas that could be causing vibrations.

Any ideas on the liquid in the prop theory Chris?

[Chris_C]

It's not so much getting the things at the correct ends, more than when they are at the correct ends you don't rotate the couplings a bolt or two relative to the propshaft.

As to the liquid... well, it depends tbh. I'm not a mech, my specialities are electronics, but my thoughts would be something along the lines that the fluid isn't directly coupled to the shaft and therefore if something goes shakey because it's out of balance then the fluid will move itself pretty sharpish. Therefore it's never part of the piece being balanced so wouldn't have affected the job, but this could be rubbish, I'd certainly have cleaned it if I could before I balanced something.

I take it we are talking drops rather than coke cans worth Though on the small dia we have a gram in the wrong place would be *very* noticable, even on some of the most dubious wheels I've seen you only have singles, maybe teens of grams added to balance.

[jon-ovlov]

Aye that's what I've done. 2 Large marks for the slide end, and 1 for the other end, scored on the side, so you know where to bolt up relative to the prop. Fluid wise it was a fair amount, I'd say half a coke can. Hence why I thought it'd throw out the balancing. I see your point though. Either way the prop wasn't balanced, as when I put the replacement front casing on, it was still shaking like fook.

[Chris_C]

Half a coke can

Surely that just drained out when it was up ended !!!!!

[jon-ovlov]

It didn't till I took it off again. Just didn't flip it the other way. It came out of an end that was supposed to be sealed. I dunno what to say really. A series of unfortunate events.

[macplaxton]

Apparently fluid in the prop wouldn't affect balancing?

It depends.

I'm not convinced by that. Balance it once, ok. Then when you restart spinning the prop, the liquid will spin possibly in a different area of the prop, affecting the balancing. Surely?

Not necessarily.

If you spin a prop to a certain set speed, the liquid will be on the inside walls of the prop. Now if the prop is at the same angle of dangle, if you spin it back up to the same set speed, it will be the same. However, for the liquid to end up in another portion of the length of the prop, the angle of dangle must change.

Using the "can of coke" as our international system of weights and measures then liquid is only going to slosh about inside if the rotational speed is below a certain point, or when suddenly accelerating/declerating through the certain point where all the liquid is on the wall. Think of a washing machine just sloshing over and going into spin. It shoogles quite a bit going into a spin, but when it's up to speed, it faily constant.

I also started talking about the weight of the prop compared to the standard one, and another chap who worked there who is in charge of balancing said "why do you need the slider? It's bloomin' heavy and is only needed really to compensate for change in suspension length". FFS.

Clowns.

Another thing was that they didn't balance the prop with the couplings at the end. But as soon as the couplings are bolted to the shaft, they become part of the shaft, so they need to be balanced with the rest it, including bolts and clamps. Surely this is right. If something is spinning at high rpm, it needs to be balanced somehow.

Yep, like Chris says, either individually, or as an assembly.

Overall, if it was balanced properly, there wouldn't have been a problem. Even with the weight, a significant part of the weight was the slider, which at the time was at the engine end of the car, not the gearbox end.

But it it may have balanced on the machine fine, but I assume that the prop fits bang on straight to balance, if this is not the case on the car, then it may start vibrating a bit then.

where as a production line balance* each component, so you can use any part in any orientation (i.e. a bucket of cranks, a bucket of flywheels and you don't have to pick out the correct ones).

*depending on manufacturer, it could be to "within a baw hair", or "f**k it, that'll do".

I've come to the conclusion (besides the general consensus that the prop is unbalanced) that:
a) the prop needs to go on a serious diet.
b) it doesn't need a slider.
c) it shouldn't be solid, but have some sort of rubber coupling in between the engine and prop.
d) may need to be two-piece to balance up right and supporting it in the middle.