just working on the cv joints on the mazda now. I have a problem: the inner CV joint on the left side reaches maximum deflection when no weight is on the wheel. I had to shorten the driveshaft by an inch, is it possible that an inch was not enough!
how many degrees of angle are the three-leg type CV joints designed to work up to! I dont want to do something like restrict suspension travel, id rather do it properly.
Any suggestions!
morrisman1,
Nov 8, 7:33pm
I should mention, it is 323 astina running gear in a mazda 121. I think the original engine sat a bit lower in the engine bay than what this one does which may be contributing to the issue
mm12345,
Nov 8, 8:19pm
I'd be perhaps making a scale drawing, and doing some measurements with a piece of string, ruler, and protractor. Tripod CV joints apparently have maximum articulation of 22 - 26 degrees or so depending on type. http://www.gkndriveline.com/drivelinecms/export/sites/driveline/downloads/brochures/driveshafts_english.pdf You also need to know (or measure) required plunge depth and calculate this as if the shaft is over-shortened (or needs to be to "fit"), then if the suspension tops or bottoms out and the shaft pulls out of the trans, you've got a real issue on your hands
morrisman1,
Nov 8, 8:49pm
will having a shorter driveshaft allow more angle! When the joint is at those high levels of deflection it is unlikely that a great deal of power is being applied and because of the low weight on that wheel not as much torque will be placed on the joint because traction will be lost relatively easily.
It is undesirable but I could just limit suspension travel and stiffen up the rear as much as I can to prevent body roll.
morrisman1,
Nov 8, 8:54pm
on a side note, I have got the engine running now. Once I sort out the CV joint, hook up the gear lever shafts, bleed out the clutch and install a radiator then it will be drivable!
Haven't done too bad for a couple weeks, especially as it is my first engine conversion in a FWD car. I must say that RWD is easier for converting, much more 'universal' than FWD cars seem to be
mm12345,
Nov 8, 9:24pm
No - it might force it though - and the only answer may be to shorten suspension travel. If the driveshaft is shorter, then I'd expect that maximum deflection at extremes of suspension travel would be increased.And if it's over 22 degrees (but not 100% sure of this) then you'll have problems. But the shaft should be the right length.So I'd expect that when the shaft is at right angles, then there's still a few mm of plunge depth left to be safe, but when the suspension is at both ends of travel, it's not at risk of pulling out. If the same hasn't been done by someone else, then I'd be doing some measurements before trying it out.
the-lada-dude,
Nov 9, 11:17am
MM read my post on yor tacho thread about limiting sus travel
pollymay,
Nov 9, 3:18pm
No, you actually need a longer shaft. Think of it like a hinge, the closer you are to the axis of rotation the more the angle changes given the same amount of lateral plane movement.
Just make sure it isn't reaching max travel in the housing or something funny like that. I've been dicking with axles lately and have mine to a T now :D
bubbles244,
Nov 9, 3:42pm
I take it there is no room under the sump to lower the engine.of course there is, its front wheel drive the subframe unbolts.
crzyhrse,
Nov 9, 4:10pm
Geometry dictates the opposite.
You've also raised the vehicle!
morrisman1,
Nov 9, 4:15pm
no, the vehicle is lowered. The engine sits a little higher than the stock engine due to different external dimensions but it isn't that much higher.
morrisman1,
Nov 9, 7:56pm
OK we got the car driving and I took it down the drive. Broke the shortened driveshaft without even trying, sheared off 8 welds. Can someone give me advice on how to properly shorten a driveshaft on a FWD!
pollymay,
Nov 9, 8:30pm
did you butt weld the cut! You can lathe them down and then fill back with weld but the other thing to look at doing is find something that will sleeve over the cut shaft. Then roll pin that and weld. Having a lathe once again helps as you can pick a nice sturdy sleeve then machine the ends down on the 2 shaft bits for a perfect fit, weld then spin for trueness. You might just have to try various size pipes and whatnot. How long is the axle! If it's quite a long one trueness is more important cause they get a whip going like old one piece driveshafts that are out of balance, shorter shafts aren't as fussy.
morrisman1,
Nov 9, 8:35pm
its the short side, about 400mm long. I sleeved it with pipe and welded through holes in the pipe to the axle. Im going to have a chat to some car builders in town tomorrow to see how they manage such a task.
My friend who is also in on the car spoke to his dad who builds the odd race car and he knows who can weld it for us but I do not know what method will be used.
I will also pull the inner CV boot off to see what that joint is actually doing and I might be able to nut out a solution from seeing it in action.
pollymay,
Nov 9, 8:41pm
what did you weld with, wire size, heat setting etc! I found if I used heavy pipe or whatever you can run a real nice deep hot weld around. A good welder will know better though. Course you can run a longer sleeve then cut the ends up so you can rather than holes have some deep trenches to run the weld along, would produce a larger surface to bind the metals
morrisman1,
Nov 9, 8:53pm
I used a mig, plug welding through tube with about a 3mm wall. I couldnt drill into the axle because it was too hard. I used the hottest setting I could on the mig which I think was 150A but it certainly doesn't feel like 150A on my arc welder.
bill-robinson,
Nov 10, 4:50am
been my experience that you will not get a cut and shut shaft to survive. Get one made, it is cheap insurance.
mrfxit,
Nov 10, 6:00am
Agreed. Also, getting the final shaft MADE, will sort out any balance issues. Theres an amazing amount of force on a very small area. Tube driveshafts have the advantage of surface area, solid rod doesn't *** BUT Taper end & BUtt welding will allow you the testing time you need. Degree's of suspension swing will need to be worked out without springs fitted (for real time movement of parts)
the-lada-dude,
Nov 10, 10:43am
your trying to welda heat treatable alloyed steel, your in dreamland with m jackson if you think you can weld it without using special rods ! all the shafts ive seen are machined to lengh then pressed / shrunk to the flange then bead welded on flange end . you'll have to find a longer shaft with the correct spline and shorten it you cant safely weld it in the middle
msigg,
Nov 10, 8:19pm
Yea not easy to get a good weld on that, like that, with that kind of metal.
morrisman1,
Nov 10, 9:12pm
got it welded today, done properly. The engineer that did it has done them before for formula ford and hasnt had any failures so thats a good start.
I also solved the CV locking up problem. I further shortened the driveshaft because the joint was as compressed as it could be so shortening brought it to about half way in the CV casing. It allowed the driveshaft to clear the housing even though the angle would be slightly more.
All well and it has stood up to some brisk take-offs but I will be sleeving the driveshaft just to give that safety factor while the strength is still unknown. Last thing I need/want is a driveshaft tearing around the engine bay destroying everything in its reach!
Thanks everyone for your input into this. I can assure you that this is a quick car, It tries to tear you off the road under acceleration but that may be a steering alignment issue. will skid up to third gear in the dry on tarmac with track tyres on and thats without using the upper rev range.
pollymay,
Nov 10, 9:36pm
I knew it could be done, it's not easy though. If you are worried about dropping a shaft maybe run a couple safety hoops, kind of hard on independent axles like that though. My honda kind of has a hoop at one end. The underbody pan I made stops the other end ever dropping down either, scare the living shyte out of you as it beats on it maybe but it won't get a big flail going and spit it out at bystanders.
morrisman1,
Nov 10, 9:46pm
The reason I want the extra safety is because I looked at the shaft when we got back and it had a whiter line in the black paint at the point of the weld. I dont know if this is due to twisting around the weld or not. anyway if it breaks it breaks but I want it to break safely
mellisa2000,
Nov 10, 10:33pm
mark across the weld with a different coloured pen, say white pen! Then look periodically to see if pen line has "Moved" or split from itself to detect twisting or separation
crzyhrse,
Nov 10, 11:17pm
Dude! That was never going to survive! The shear stress on each plug weld would be enormous.
Glad you found someone who would do it properly.
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