Really?????????

If your busting all your good stuff, maybe I'll have a shot

Well,

I woke up this morning with a runny nose and a tickle in my throat so decided not to head to church. Maybe that's it? Nah...........

I think the problem is I didn't follow Paul G's suggestions to a "T" and thought I could get away with not using a stud.

crankbndr wrote:If your busting all your good stuff, maybe I'll have a shot

yeah maybe......... I am toying with the idea of making an order. I wish I had a driveplate for a car crank. Those things are stout.

Godsey3.0 wrote:Wow. Apparently you have upset some sort of Performance God. Time to seek forgiveness.

Rolla

I agree pray to the Michelin man in the sky !!

Ugh Ron,
Trying to put myself in your shoes.
Maybe something's happening while you're
installing the drive plate, like the stud/bolt
bottoming out before the plate is fully seated.
That might put quite a strain on the splined
section of the crank.
Bad mojo at any rate. Good mojo you weren't
hit either time.
Bob

Get some stud spinners instead of the screw spinners. Getting expensive...

Phil

Ron I am just too danged lazy to look it up...I see you have a cap socket hardened screw

5-40 thread has a specific "yield" max torque and without looking it up in the engineering book I know is is very very low inch pound spec...

I suspect you are over torquing the prop screw my friend.... ANY imbalance laterally on an over torqued fastener is going to cause exactly what you see here

A longer prop-screw will grip further in too, and reduce the stress on the outermost part of the crank.

I suppose I should have prepped a little better for this I agree. The splined end broke off the crank the screw didn't fail. The Mouse building guide does say use a stud as opposed to a screw to prevent this sort of thing happening. I am learning.......

Fred, I usually just snug props and rarely overtighen anything, but it's not out of the realm of possibility.

You just can't win! Try a DDD crank, those are pretty solid. Its just finding one with the best fit.

We have never heard of one of our KB cranks breaking during use, even with diesel operation. That is really strange as they are hardened to HRC58 and should withstand 30,000+ RPM. This is the same hardness that Valentine uses for engines that even spin faster than that.

Again, if the crank originated from us let us know and we will happily replace it.

This is an "old" problem, the prop-screw needs to reach deeper into the crank.

Surfer_kris wrote:This is an "old" problem, the prop-screw needs to reach deeper into the crank.

This is why I buy longer prop screws, then cut to a length where it tightens up just before it bottoms out in the crank. That gives the maximum thread depth and provides additional support to the crank as far as possible.

This is one of those "As Is" cranks Bernie.......

So as such it was a risk to begin with. I have the mouse where I want it. Going to start from scratch on the unlimited as I have a vibe issue going on and It doesn't matter what crank I put in it. It was my novice entry from last year and I wonder if the case is toast.

andrew wrote:

Surfer_kris wrote:This is an "old" problem, the prop-screw needs to reach deeper into the crank.

This is why I buy longer prop screws, then cut to a length where it tightens up just before it bottoms out in the crank. That gives the maximum thread depth and provides additional support to the crank as far as possible.

Yep, that's the plan. Headed to the hardware store tomorrow..... I figure a longer screw or a stud is pretty much the same.

Ron

The was a farmer who's donkey died.
He said " ooooh aaaarh he never did that before".....

However we know these do fail.
Rons had 2, I've had 1, it sounds as though Paul G
Has had several.
So Whaddyall gonna do?
That's right get smart and if you run performance Cox's
Stud and nut it.
1,There's a very good reason us performance car nuts always
Get rid of rod bolts and cylinder head bolts in favour of
Studs and nuts,
2, why is it most (if not all) other engine manufacturers have
A Nut? On my YS's we even have 2 nuts just to make sure.

Probably about time it was recommended as the First Thing
To upgrade. It could even be a feature in this quarters magazine.

In fact I'm only thinking out aloud here....
Perhaps the kb cranks should be sold with
A stud and nut?

As for hardened bolts.....
In Europe any bolt of 3mm or less
Cannot be certified as high tensile.
I shalln't bore you with the science
Just take my word for it, sometimes
Bolts are not a good idea.

cribbs74 wrote:

andrew wrote:

Surfer_kris wrote:This is an "old" problem, the prop-screw needs to reach deeper into the crank.

This is why I buy longer prop screws, then cut to a length where it tightens up just before it bottoms out in the crank. That gives the maximum thread depth and provides additional support to the crank as far as possible.

Yep, that's the plan. Headed to the hardware store tomorrow..... I figure a longer screw or a stud is pretty much the same.

Ron

5-40 is an odd size. For some reason stores skip it and sell #4 and #6, but not #5 screws. Good luck finding them Maybe if there is a Grainger in your area they might have them. They don't have #2-56. Radio shack actually sells #2 screw, washer and nut assortments of pretty good metal.

McMaster-Carr carries an extensive selection of 5-40 socket head screws:

http://www.mcmaster.com/#socket-head-cap-screws/

cribbs74 wrote:This is one of those "As Is" cranks Bernie.......

So as such it was a risk to begin with. I have the mouse where I want it. Going to start from scratch on the unlimited as I have a vibe issue going on and It doesn't matter what crank I put in it. It was my novice entry from last year and I wonder if the case is toast.

So sorry ..... but the "as is" were greatly discounted to reflect the fact that they are not "perfect" and likely should not be used in max performance applications.

But, I know of a Green Hornet that will have a nice spare KB crank attached to it

Actually ...... cribbs = not Travis, correct? In which case the last post of mine is to be ignored as I am obviously confounding you with another "74" that won one of our auctions on the weekend