Truing the DRZ crank

[Michael Woodcock]

So I've 3d printed the crank truing stand, I'll upload that to thingiverse soon, may make some improvements first.  It uses skate bearings. 

 

The crank is well within spec.  maybe .04mm max at the very ends of the crankshaft.  I've never trued a crank before, this is my first time measuring one even.  The manual shows where to measure it. I'm curious if it's even worth the trouble to try and get it perfect, probably not obtainable.  

 

Obviously I can't smack the crank on these PLA stands 

[Michael Woodcock]

ok I actually just smacked it with a hammer anyways, even though hit was "close enough".  It is easy to make it "better" but seems hard to get it "just right".  about .025 if I give myself the benefit of the doubt now!  probably .03 if I'm honest

Edited June 24, 2019 by Michael Woodcock

[Noble]

You really need 2 dial indicators on the crank at the same time to get an understanding of how the crank is out true - pinched in, spread put, or twisted.

[Michael Woodcock]

5 minutes ago, Noble said:

You really need 2 dial indicators on the crank at the same time to get an understanding of how the crank is out true - pinched in, spread put, or twisted.

Ah that makes sense.  I could have a little bit of all 3.  Crank had a high spot and low spot not 180' apart

[roleyrev]

I'm keen to give that a go. Plenty of time, just when you think it's ready

[Michael Woodcock]

I think it's done to my abilities now, see here: 

https://www.thingiverse.com/thing:3710984

the last design is functional, but if you really press hard the dial moves from pressing.  I looked at the stand very thoroughly after designing the new one, and you can actually see the problem is the base isn't perfectly flat, and the base bends slightly when you push down really hard.  Hopefully the new design minimizes flex, but it may be even more beneficial to make a little shelf to hold the dial gauge

 

P.S. 

modifier for the top where the ebarings go,100% infill there.  I havent tried the new design so if you do please post a make!

Edited June 24, 2019 by Michael Woodcock

[pecor]

Ya, Without the proper V-Blocks and a Granite Surface plate, Your just throwing darts,  If your concerned about the run-out, Take it to a shop and have it done Right. ?? 

[Michael Woodcock]

4 hours ago, pecor said:

Ya, Without the proper V-Blocks and a Granite Surface plate, Your just throwing darts,  If your concerned about the run-out, Take it to a shop and have it done Right. ?? 

FWIW, a lot of professional crankshaft truing stands use bearings:

https://www.walmart.com/ip/K-L-Supply-35-9577-MC310-Indicator-Arm-Assembly/53395875?wmlspartner=wlpa&selectedSellerId=1148&adid=22222222227044585121&wl0=&wl1=s&wl2=c&wl3=94104129050&wl4=pla-216385611170&wl5=9011287&wl6=&wl7=&wl8=&wl9=pla&wl10=112562587&wl11=online&wl12=53395875&veh=sem&gclid=Cj0KCQjw6cHoBRDdARIsADiTTzY4Eo65AeEo43qk58fkbobjQfsaSCAl68TJySQ-OhP5-ziXL8KEMIAaAgTGEALw_wcB

 

I'd prefer one of these, or v blocks & a granite plate, or a large lathe with dead centers better than this, but it's what I've got right now.  In the future, that K&L truing stand sure looks nice and It's probably what I'll get, since motorcycling is turning out to be a lifetime hobby I can share with kiddo.  

 

Also FWIW, I've unfortunately worked at a few shops in my neck of the woods.  The last one I worked at just didn't do that kindof work anymore.  When I asked why, they just said in a beating aroud the bush kindof a way "There's more money to sell them a brand new crank".  They cleared out the shop one day and I scored a boring bar, just like the one racetech uses.  It's a shame, really.  Such a throw away society these days.  I have thought about sending it off to get it trued and welded though

[38super]

You'll need a lead hammer too.  I would use a 0.0001 dial indicator, BMW twins use build up cranks and they indicate to 0.0005" TIR.