20/2 crank gear

[oliver90owner]

XYZER,

I bet $100.00 Dursely or the Indians didn't put the crank in a freezer and heat the gear

I would not expect, and cerainly didn't suggest, they did.

All the freezer does is give an extra near 60⁰ delta T for no particular effort.  Might be important if that gear is susceptible to heat treatment.

I might have taken you on with your bet if you had said 'or' instead of 'and'.  I think you chose your words carefully.  You are running against the tide here, so start paddling!!

Regards, RAB

[XYZER]

The question.........

Well I finally got time to work on the engine. Based on advice from the thread on the 14/1 crank gear I prepared to take the crank gear out of the engine. However I soon realized that this is not necessary. After removing the idler gear and crank balance weights one can reach the back side of the roller bearing and tap it off the crank. Then the broken gear slides right off. I found no damage to the crank.

To install the new gear I plan on heating it in an oven, however I really don't know how hot to get it. I'm thinking around 400* (f). What do you guys think??

Rab,
I have done my share heating and shrinking and am fully aware of the coefficient of expansion/contraction and how it relates to temperature. Reading the OP and his situation of a down motor off grid away from town and living in Montana some where with a crank still in the engine and that was my answer and I am sticking to it regardless of your opinion of the tide and which direction you believe it is flowing.

XYZER,
I might have taken you on with your bet if you had said 'or' instead of 'and'.  I think you chose your words carefully.  You are running against the tide here, so start paddling!!
Regards, RAB

Me.....choose words......FUC$ NO!.....I told him how I would fix it in the situation it is in and why I believe it an acceptable method! If you all think it just easy to heat a gear and slide it nicely on down inside the crankcase over the crank and get it properly timed FAST! well jump on the boat and ride that tide!.... I would clean up the surfaces and press it on like it has been done for years. Is it the perfect way?.....NO! Will it work in his situation?...YES! We maybe also need to mention some of the pitfalls of shrink fit.....like if it cools before you get it where you want it....that will piss you off!.....Then what?
Dave 

[vdubnut62]

If the engine in question is in Montana, it's in a freezer already! It's 11 degrees here, and I'm in Tennessee.
In weather like this, a Bic lighter would provide enough heat to the gear. Almost. 
By the way just what is a "Delta T"?  I missed that day at Percussion U.
Ron

[mobile_bob]

somewhere in the discussion i lost track of the OP wanting to reinstall this gear with the crank in the engine,

no way i would even think to attempt this feat myself, the crank would have to come out so that i could get it
standing vertically, and perhaps most importantly, so i could closely inspect for burrs and other high spots that
would cause grief getting it back on.

sure couldn't hurt to chill the crank, and having an extra set of hand with a length of angle iron to index the drop
would be handy as well.

probably ought to mic the crank od and the gear id to see just how tight this fit really is?

don't know whether or not i would bet on precision from the indians, and precision in this area is the difference
between a heat and shrink, and how hot you will need to go?

bob g

[Crumpite]

If the engine in question is in Montana, it's in a freezer already! It's 11 degrees here, and I'm in Tennessee.
In weather like this, a Bic lighter would provide enough heat to the gear. Almost. 
By the way just what is a "Delta T"?  I missed that day at Percussion U.
Ron

Engineering jargon, it means the difference (delta) of temperature between two places, i.e. the gear and the crank.

Daryl

[oliver90owner]

Xyzer,

Please read the thread.  In my response (8th post on the thread?) I wrote, quote "Either way, I would not even attempt it with the crank in situ."  Anyone attempting a repair like this in situ - well, I say best of luck and get on with it.  You really need to keep up with the ball game and stop taking things completely out of the context of the posts.

Read my post again, carefully.  You chose your words carefully (or maybe by luck, I dunno), but you said heating and freezing.  If you had said, as I posted, heating or freezing, I could have won the bet  but as you had said and you made it a no win odds, there was no point in betting.  

If I were a manufacturer using a shrink-fit method, I would choose either heating or cooling, not both together.  Certainly not 80 years ago.  So your bet would be a no-brainer.

I often ask students for the probability of getting a head or tail when tossing a fair coin.  You might be surprised how many get the answer wrong and say 'evens', 'half', or '50%'!  They just a) don't listen to the question or b) don't understand why their response is wrong.

RAB



The correct answer is 'certain, 'one' or '100%', btw.

[Fat Charlie]

I call edge.

[TimSR2]

Supposing I was freezing my ass off  offgrid this is how I would handle it.  Mark new gear clearly with an index mark.  Same for the crank. Scribe a line down the crank to line up the gear.  Prepare a mild steel pipe driver of appropriate size.   1, 2,  4 and 8  pound hammers handy. Heavy  brass punches at the ready for emergency adjustments to gear rotation. Polish crank with emery. Dry  crank journal surfaces to reduce heat transfer.  Heat up gear in oven to 450 f  set up a brick in the shop with a rested tiger torch or hotplate to keep it real hot till you are ready to install it. Use leather welding gloves.  Line it up and smack it home like a wheel bearing.

If you are a  couple degrees out she will still run fine at reduced output and you can fix it in the summer. 

Tim

[akghound]

Supposing I was freezing my ass off  offgrid this is how I would handle it.  Mark new gear clearly with an index mark.  Same for the crank. Scribe a line down the crank to line up the gear.  Prepare a mild steel pipe driver of appropriate size.   1, 2,  4 and 8  pound hammers handy. Heavy  brass punches at the ready for emergency adjustments to gear rotation. Polish crank with emery. Dry  crank journal surfaces to reduce heat transfer.  Heat up gear in oven to 450 f  set up a brick in the shop with a rested tiger torch or hotplate to keep it real hot till you are ready to install it. Use leather welding gloves.  Line it up and smack it home like a wheel bearing.

If you are a  couple degrees out she will still run fine at reduced output and you can fix it in the summer. 

Tim

That is just what I did .... well almost.
I heated the gear in the cookstove oven to 500*(f) in a cast iron pot.


Then I took it out to the generator shed and drove it on with a post driver.

Pretty simple.

When I put the bearing back on I adjusted it so there is zero (Tight) end play on the crank. Keep in mine that I used the old bearings. I did however replace the rod bearings.
Ken Gardner

[TimSR2]

Congrats! is she running?

Zero end play seems a bit tight... I'd want  .010 in. or so

Tim

[TimSR2]

Oh never mind. I just looked at your pics again.  I see you have TRB's instead of plain shells.

[oliver90owner]

I know, I know, the Indians smack everything together with a big hammer.

But did you know that they knew 70 years ago, and more, that you do not strike taper roller bearings with a steel hammer?  Little wonder they fail early.

For instance, my Wisconsin VE4 service manual (1940s?) warns of the consequences of doing that with a TRB crank.

RAB

[mobile_bob]

interestingly the japanese have a different attitude about how to install brgs
they ascribe to the use of a hammer and hardened punch!

their reasoning is chips generally fly out!

lmao, this is true, i got this from nissan back in the late 80's
perhaps they too have changed their attitude on this topic

of course they didn't have anything to say about the use of a sledge hammer

nevertheless, i still use a brass drift for the most part, a soft steel drift and sometimes a
standard punch if the brg surface is large enough. they are very easily chipped with an errant blow.

bob g

[akghound]

of course they didn't have anything to say about the use of a sledge hammer

bob g

What do they say about using a post pounder? 
Actually I set the bearing with a brass punch and a few taps from a light weight hammer.
Ken Gardner

[vdubnut62]

If it was costing $20 a day, I'd beat the SOB on there with a damn rock if I had to!
Ron