Driveshaft speed would absolutely be dependent on Engine rpm.
I did some quick mathing, and if I assume a reasonable rev limit of 6000 rpm, then I get the following driveshaft speeds:
1st - 3.71:1 - 1618 rpm
2nd - 2.19:1 - 2740 rpm
3rd - 1.54:1 - 3906 rpm
4th - 1.18:1 - 5098 rpm
5th - 1:1 - 6000 rpm
6th - 0.83:1 - 7212 rpm
So the driveshaft definitely CAN get above that 3K balancing speed. Mind you, in the higher gears that rev limit gives some mighty high speed! The 3rd gear would be 74 mph, but then the 4th is 109, 5th is 128, and 6th is 162. Those last three numbers maybe aren't realistic on a street / autox car.
Or I'm not fully understanding the situation.
Or the 3K is good enough and I should quit worrying.
You explained it way better than me. I was thinking about it relative to wheel speed, vs relative to rpm/gear.
Ill go back to lurking now....
In reply to Dusterbd13-michael (Forum Supporter) :
No, you're good. You keep me honest!
I think you're good. Let me ask you in this way. Would spinning it faster than 3k make it less balanced? I understand yes the centrifugal forces are higher but would it really make a difference?
In reply to Stampie (FS) :
I dunno. That's why I'm asking. I know someone was talking about shaft balancing at 10k. Big difference.
Amongst other considerations, every unbalanced drive shaft I have encountered had a serious resonant shake somewhere in the 3000 RPM range. All of those were on live axle cars and longer shafts too. Mark2 Jag sedans mostly, they were sensitive. Never encountered one with a fixed final drive setup.
TurnerX19 said:
Amongst other considerations, every unbalanced drive shaft I have encountered had a serious resonant shake somewhere in the 3000 RPM range. All of those were on live axle cars and longer shafts too. Mark2 Jag sedans mostly, they were sensitive. Never encountered one with a fixed final drive setup.
That's as good an explanation as I need right now. I've got some serious E36 M3ting or off-pot-getting to do.
It may have to do with vibrational physics. There are resonant frequencies in any structure, and spinning the shaft at 3000 RPM may be good enough to test for the lowest frequency for an average driveshaft. Spinning it faster will just find the higher frequencies. I'd go with the experts on this.
In reply to JoeTR6 :
Yeah, I think I'm starting to understand all the factors here. I think I'll just order the shaft locally and get on with it.
Steering rack is coming together. Big thanks to Joe TR6 for offering me his big box o spare parts!
I blasted and painted the hood latches today. I tried to take them apart more, but the connecting bushings refused to budge. So onward!
I also am working on getting the rubber isolation pads in. I have two more to go.
I'm looking to start reassembly on the intercooler, so I pulled out the bead roller.
I found it likes to waiver off the straight line, so I spent a little time on the lathe and made this stop:
Runs much more true now. The magic distance for the stop seems to be 1" from the tube end.
Ok, I just dropped by the driveshaft shop and picked up the slip yoke and rear flange. I wanted to give them a real fit check before they built the shaft. David at the Colorado Driveshaft was very supportive of me doing this. I was a bit worried he'd think I was being stupid, but he's a measure-once cut-twice kind of guy.
Perfect fit!
I also got to take a real fitting-to-fitting dimension for them:
That's with the slip-yoke fully pushed in. David recommended 3/4" of extra play, just to give me a bit of wiggle room on the installation.
Now that I sent in the dims, he's going to get the shaft all welded up and balance. Then when I go to pick it up he'll press on the ends. Nice that he can save me an extra trip across town.
A nice move forward today.
Could you measure the dimensions of the flange? Especially then locating ring? Like really measure in that I might ask you to make an Scott Special adapter for me?
Stampie (FS) said:
Could you measure the dimensions of the flange? Especially then locating ring? Like really measure in that I might ask you to make an Scott Special adapter for me?
Yeah, absolutely.
The pilot bore I happen to know off the top of my head - 50 mm.
In reply to TVR Scott (Forum Supporter) :
Could you also grab an OD measurement of the slip yoke? My Aerostar slip yoke fits the splines but the seal isn't tight, looking to see where the difference is.
Ok, here are some measurements for you.
Slip yoke OD:
Flange pilot diameter:
Bolt circle. Bolt holes are 12mm, btw. Pattern is square.
And corner-to-corner on the flange. (Casting is rough, so this one isn't very precise)
What else?
TVR Scott (Forum Supporter) said:
Ok, here are some measurements for you.
Slip yoke OD:
Thanks! That's the same as my Aerostar yoke. I wonder why my output seal is so far away from touching it.
stphnclrk1181 said:
In reply to USERNAMETAKEN :
This TVR is a beauty.
Thanks! It's getting there!
TVR Scott (Forum Supporter) said:
In reply to damarble :
Worn out seal?
Maybe, but it's a really big gap all around. Something like 1/4" or so IIRC. It looks like a new seal should fix me up.
I forget, did you go NC1 or NC2?
damarble said:
I forget, did you go NC1 or NC2?
I'm embarrassed to admit I don't remember. I think it was a 2007 gearbox, but it's been like 2-1/2 years. Are there any indicators between the two?
Edit: I found the receipt - it's from a 2006.
In reply to TVR Scott (Forum Supporter) :
Externally all I can say is different is the VSS sensor hole is not machined out on NC2. NC2 is supposed to be significantly stronger and shift better so that's what I went for since it was only an extra $200.
Now I have to see if the seals changed between them.
My buddy Kolby came by this morning and we did a whole bunch of stuff on the car.
He torqued and striped a bunch of bolts on the suspension that I'd missed, and then got the radiator put back in. Filter relocation plate torqued down too.
I focused on getting the steering rack put together and properly shimmed.
Dialed in the preset really nicely here - 0.006" on the nose:
I reused the old long inner tie-rods, just so I could get things bolted up and on for now. In!
From the other side:
And the impossible to see shot from above:
The rack is definitely coming back out for bump-steer length corrections. I'm pretty sure I've got a good plan there, though. Gotta order some materials and tooling.
Great day!
