alistairolsen
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| posted on 17/2/10 at 12:07 PM |
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O/T driveshaft joint query
If I wanted to link an engine to a single shaft where the engine was free to move in rubber mountings and the shaft was fixed solid in a bearing (much
like a locost engine and a bolted diff) with the shortest possible distance between the two parts, what would be the best way?
Would a propshaft with very little tube work? just the two joints back to back?
Aqua drive do a combined cv shaft and thrust bearing:
Aquadrive
which is ideal but hardly locost. I'd like to replicate this effect as cheaply as possible! Perhaps sierra CVs on a short shaft?
Any ideas?
Cheers!
PS, has to handle ~250bhp
[Edited on 17/2/10 by alistairolsen]
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mad4x4
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| posted on 17/2/10 at 12:40 PM |
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Yeah two Uv joints should work
The length will be a function of the maximum angle the UV's can work at versus the Offset between the connecting componets.
Personally I would try and get them as aligned as possible...
Got a feeling a BOFFIN will come along shortly and put the science to what I said.
[Edited on 17/202/10 by mad4x4]
Scot's do it better in Kilts.
MK INDY's Don't Self Centre Regardless of MK Setting !
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Angel Acevedo
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| posted on 17/2/10 at 12:44 PM |
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What is the distance between the two?
How much do you expect the motor to move?
It all comes to the angles involved by a combination of the two.
If small enough, I´d go for U joints.
Else, CV Joints.
What about a Torque tube to join both?
HTH
Aaarrrggghh!! SLOW!!
AA
[Edited on 2/17/2010 by Angel Acevedo]
Beware of what you wish.. for it may come true....
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tegwin
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| posted on 17/2/10 at 01:00 PM |
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On light hovercraft the engine usually sits about 10" from the solidly mounted lower pulley shaft..
Something like a Bullflex rubber flexible coupling is used...
Assuming the shaft and engine are aligned well enough that works really well...
Helps cut down noise/vibration transfered to the rigidly mounted fan frame too..
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alistairolsen
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| posted on 17/2/10 at 01:05 PM |
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alignment isnt an issue, that can be made spot on.
distance wants to be as short as possible, limit will be the joints back to back and getting access to the circlips and stuff Id have thought.
Engine movement, no idea! Its a BMW straight 6, fixed to a propellor (no transmission shunt) mounted in 4 landrover v8 mounting bobbins.
what do you mean by a torque tube?
bullflex coupling is just a ruber donut sandwiched between two bolted flanges? I have one of those on the gearbox output shaft just now.
cheers!
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MikeR
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| posted on 17/2/10 at 01:19 PM |
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how fast is the boat?
or are you worried that climate change will mean you need a REALLY powerful ceiling fan?
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alistairolsen
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| posted on 17/2/10 at 01:24 PM |
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Its an 18 foot deep-V hull with a flared bow and strakes fitted with a surface piercing drive with a 14 inch propellor.
All up weight will probably be sub 700kg.
Engine is a BMW 2.5 24v six with a homebrew turbo conversion.
The boat previously had an outboard and did 64mph down Windermere with a 150hp outboard. Id like to see 80mph ultimately (in very very flat water)
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tegwin
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| posted on 17/2/10 at 11:07 PM |
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Any pics!!???!!
Also... any chance you could measure the engine? Im curious to know if a BMW 6 would fit in my TVR!
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alistairolsen
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| posted on 18/2/10 at 07:37 AM |
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Pics, Ill try and get some, its a long term mothballed project buried under piles of junk in a spare garage!
As for the engine, Ill measure it when I get it, its in a mates lockup 100 miles from either of us at the moment!
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Nisseven
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| posted on 18/2/10 at 11:11 AM |
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I have a small jet boat that has the engine coupled to the jet unit with a Hillman Imp driveshaft rubber donut. A common coupling to use is out of a
BMW which it sounds as though you allready have, so use that. Motor won't move much and if it does will tend to rotate around the crankshaft so
no problem. Only thing I would do is to remove the spigot that aligns the coupling in the BMW driveshaft (if it has one as I think they do), you
won't need it.
Bruce
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Angel Acevedo
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| posted on 18/2/10 at 04:51 PM |
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Torque Tube
quote:
Originally posted by alistairolsen
alignment isnt an issue, that can be made spot on.
If you will be using U Joints, zero alignment may lead to premature failure.
Yo would want a few degrees angle and that leads to the use of two UJ.
This is not a problem with CV joint.
quote:
Originally posted by alistairolsen...distance wants to be as short as possible, limit will be the joints back to back and getting access
to the circlips and stuff Id have thought.
Engine movement, no idea! Its a BMW straight 6, fixed to a propellor (no transmission shunt) mounted in 4 landrover v8 mounting bobbins.
quote:
Originally posted by alistairolsen...what do you mean by a torque tube?
Torque Tube is a Tube that connects engine and transmission and then they move as a single unit..
Yo will need to provide a flexible joint at the shaft through hull point to permit this movement
Beware of what you wish.. for it may come true....
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alistairolsen
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| posted on 18/2/10 at 08:45 PM |
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yeah, Ive seen the alignment thing for propshafts in cars before and hence would rather use CVs.
The whole point is that the shaft HAS to be fixed as it runs in fragile lip seals, so the engine needs to move independantly.
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