IRS vs Swing Axle

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C J Murray
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Re: IRS vs Swing Axle

#16 Post by C J Murray »

Dad, Is the half-shaft length fixed therefore providing the lateral stability?
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C J Murray
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Re: IRS vs Swing Axle

#17 Post by C J Murray »

Of course, if you develop a swing axle gearbox that is very strong and has a variety of ratios you can add the racing community to the client list. The racing version would be limited by rules to 4 speeds but that would be fine if it was designed for extreme use.
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Jacques Lefriant
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Re: IRS vs Swing Axle

#18 Post by Jacques Lefriant »

CJ
we have to come up with the trailing arm.
DSC_0084.JPG
this is off a 924 and is not as adjustable as the 901 i would use needle brgs like the 901 rather than the roller pictured in the axle picture for the inner brg the trailing arm would be threaded to accept the normal 3 bolts from the upright. toe in as before. camber would not be adjustable like the 901. the pivot on the forward end could even go to a clamp on or welded receiver at the tube. real racers might cone up with links to the gear box and inboard brakes like my SM.
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Jacques Lefriant
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Re: IRS vs Swing Axle

#19 Post by Jacques Lefriant »

CJ that would be a Hewland MK9 dog box but it would require finesse in shifting.
Early MK9s used the VW tunnel case and stock VW R+Ps the Rhino case is now used by rebuilders but the old internals are hard to come by. Webster also made parts for the box Most small formula cars use them Greg has one in his Elva and the 911 Bobsby uses it. Mendeola/weddle have offroad versions that have synchro internals. 4spd versions are shorte rand they fit between the engine and the torsion tube. 5spds are problematic. The offroard community moved reverse and made it stonger but then the box gets longer. pick your poision.
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Craig Richter
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Re: IRS vs Swing Axle

#20 Post by Craig Richter »

IF my 356 had 25" OD (stock) tires, AND it had a Normal (stock) motor, AND it had your 8:31 (3.875) with stock gears, I think I'd like it a lot. 1st gear is awfully high, but 1st is rather high anyway in a 356, and the other gears fall in place nicely, without that horrendous gap usual with a 4G. A hoped-up motor (lots of cam), won't much like that high 1st gear, but Normals or Cliff's monster motor should pull it nicely!
Tossing a lightweight Speedy with 23.5" sticky tires around the canyons and mountains where I live would be most fun with a 7:34 (4.85) like the B-in-law's, which gives a nice low 1st for those mountain switch-backs and drag race starts, then a nice high 4G to make freeways livable. 2 gears in between just isn't enough.
 

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Vic Skirmants
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Re: IRS vs Swing Axle

#21 Post by Vic Skirmants »

The racers of 356s are not only limited by the number of permitted gears, they are limited by a rule that says stock suspension; and yes, Cliffy, I would look under any tub that outcornered our usual quick suspects.

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Re: IRS vs Swing Axle

#22 Post by Jacques Lefriant »

Hi Vic
aren't the internal gearbox parts free. how about the case? and are coil overs permited?
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Re: IRS vs Swing Axle

#23 Post by Adrian Rendle »

Jacques, parts are getting so scarce, would it be out of the question to just manufacture your own trailing arm, which could incorporate eccentrics to make the positioning of the inner pivot plates (welded to the t-bar tube) less problematic...the cost of the special g/box side covers would probably be just as significant
but, if a 5th gear wasn't available (without cutting out large chunks of the t-bar tube to fit a different box), i doubt you'd get many takers

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C J Murray
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Re: IRS vs Swing Axle

#24 Post by C J Murray »

I have no idea what Vic is talking about.
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Re: IRS vs Swing Axle

#25 Post by C J Murray »

Jacques, can the pinion shaft be moved farther from the mainshaft to engage the ring gear in a different location, making room for more robust gears and mainshaft and bearings, that might also allow more narrow gears that would make room for a 5th gear??? I assume that would require a redesign of the R&P teeth? This post should expose my lack of understanding of gearboxes.
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Martin Benade
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Re: IRS vs Swing Axle

#26 Post by Martin Benade »

Moving the pinion shaft would make it into a hypoid gear set, which is not uncommon on other cars. The rest I leave for Jacques.
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Re: IRS vs Swing Axle

#27 Post by Jacques Lefriant »

CJ and Martin you are both right. If we move the ring gear by the same amount we don't need to employ a hypoid. so there are a lot of spiral bevels that would work and they can be fliped for mid engine. The hypoid gives us more room but it was only used in the G50 by Porsche so it would be a big generational jump.
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Re: IRS vs Swing Axle

#28 Post by Craig Richter »

Cliff, your idea of moving the pinion to gain some space sure sounds worth pursuing to me. Someone's going to have to think a little out-of-the-box to get this project done. This afternoon Jack was explaining to me some problems with the position/angle of the shift shaft with some of these proposed trans cases when used in a 356. There are a lot of things to get right. The guy who finally makes a proper 356 bolt-in 5-speed (and @ 10K or so) is going to have his picture placed next to the good Dr. and become a very famous and almost rich guy!
 

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Re: IRS vs Swing Axle

#29 Post by Jacques Lefriant »

Hi Craig
the Rhino case Gene Berg 5spd or a look alike is very doable for under 10K.
DSC_0089.JPG
a simple sand casting could be made like these my associate is doing for Weddle for a VW based box. it could incorporate the ears for mounting no there is no room for a 6spd although with 4 shift shafts you can do 7 and reverse but it gets too long.
 

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Re: IRS vs Swing Axle

#30 Post by C J Murray »

Jacques, my adoptive Dad, is the man for the job. I am certain that he could do it. Swing axles and VW hot rod parts are the way to go with a variation on the case to make it fit an unmodified chassis. Right off the bat you can see that Jacques has the right contacts and knowledge of the available VW stuff. All we have in PA is down power wires and ice.
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