20/2 crank gear

[akghound]

Well I finally got time to work on the engine. Based on advice from the thread on the 14/1 crank gear (http://www.slowspeedengines.com/forum/showthread.php?t=739) 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.

 

You can use the oiler tube as a tool rest




Broken gear


Bad Crank Gear AND Bad Idler Gear
This is getting worst rather then better

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??
Also posted at http://www.slowspeedengines.com/forum/showthread.php?t=770
Ken Gardner

[dubbleUJay]

Ken. I cannot go to that link you provided and the registration seems to be disabled!?!
What gives???

[mobile_bob]

if i recall correctly there is no keyway and key to position the gear, so it must fit pretty darn tight
so i would expect 400 degree's is not quite hot enough

if memory serves me the gear on a new crank has a dark purple or almost black look to it, telling me
it was heated to ~650 degree's F

now here is the fun part, you must make absolutely sure the crank has no burrs or scars that will impede the
hot gear from sliding on fully. stone, file or sand down any such blemish very well, make sure there is nothing to
hold up the gear or get caught under it, otherwise it will go on part way and you will be forced to use the indian
golf club (sledge hammer) to fully seat it.

depending on the bore size it might sit onto a 100 watt light bulb in a lamp, just sit the gear down on the bulb
and let it heat up, check the color and when it goes from full blue to dark violet/purple it is about as hot as it needs to
be,

pick it up with welding gloves and slip it onto the crankshaft, being certain to position the teeth where they ought to be.

probably a good idea to have a section of pipe to use as a driver to finish the install should it cool and lock down before it seats fully
far better to finish driving it hot that wait till it cools and then have to beat the crap out of it to get it seated, and probably set it up
for a crack in the process.

if you find after heating the gear it still won't start on the crank, it may have to be even hotter, i don't know how tight a fit they make them.

bob g

[XYZER]

Getting it on is easy....but getting it timed properly may be a stinker! Geno supplied us with this excellent representation of the proper timing of the crank gear on a 6/1.....I'm guessin it's the same for the twin.

[vdubnut62]

Its going to be darn near impossible to juggle a 600 degree gear, drive it onto the shaft before it cools---in EXACTLY the right orientation.
Your not gonna get a second chance on moving it around if it's wrong.
I'll bet the gear was heat treated, annealed, hence the color Mobile_Bob noted, then pressed on cold. Or driven on with a piece of pipe and what somebody here aptly called an Indian golf club. (sledge hammer)
Ron

[Geno]

This post puts my pic on the Microcogen.info server for future reference if my site goes down or something. That's a Dursley crank as well.

Thanks, Geno

[XYZER]

Your not gonna get a second chance on moving it around if it's wrong.
I'll bet the gear was heat treated, annealed, hence the color Mobile_Bob noted, then pressed on cold. Ron

I have to agree with Ron....I would get it in correct timing rotation and drive it on....

[oliver90owner]

I would get it in correct timing rotation and drive it on

I would respectfully disagree. I would not just drive it on unless as a last resort.

I would have the crank in a freezer on super-freeze at near -40, if there was not a local supply of dry-ice (or even a dewer of liquid nitrogen), or stood outside if colder, the gear mounted securely in a large easily-located block and heated in an oven. Two reasons - firstly for easy location in the correct orientation and secondly as a large heat energy store so the gear will not cool quite so quickly.

Either way, I would not even attempt it with the crank in situ.

Regards, RAB

[WGB]

I would get it in correct timing rotation and drive it on

I would respectfully disagree. I would not just drive it on unless as a last resort.

I would have the crank in a freezer on super-freeze at near -40, if there was not a local supply of dry-ice (or even a dewer of liquid nitrogen), or stood outside if colder, the gear mounted securely in a large easily-located block and heated in an oven. Two reasons - firstly for easy location in the correct orientation and secondly as a large heat energy store so the gear will not cool quite so quickly.

Either way, I would not even attempt it with the crank in situ.

Regards, RAB

I would agree with RAB, that is how I do most of my press fit work.

[vdubnut62]

I evidently gave the wrong impression, I was not advocating driving the gear on cold, that would be my last resort.
Placing the crank in the freezer and warming the gear seems to be the best option so far.
I would probably try my best to discover how the "Dursley Boys" did it since it does seem that their method worked very well.
That being said, I will still bet that the  Indian OEM procedure was a large pipe and an even larger hammer  at ambient temperature.
Ron

Attention Moderator: We need a smiley whaling away with a gigantic hammer!

[vdubnut62]

oliver90owner, I am curious to know what kind of large block you mean? Something out of iron?
This sounds like an example of something I need to learn and file away for future reference, I hope I never get too old or stubborn to learn something new.
Thanks, Ron.

[oliver90owner]

I'll bet the gear was heat treated, annealed, hence the color Mobile_Bob noted, then pressed on cold.

Ron,

I fail to understand how I could have got the wrong impression from your post!

Steel is cheap and available.  Chocolate would not do!

I would probably resort to machining a relatively massive (wrt the gear) holder to do the job.  Right size, good thermal contact with the gear and with the gear securely fixed in position to be assured of good angular alignment.  So probably cut and bolted together.  Do one, do a hundred, the tool for the job would be a one off, so relativley expensive.  Probably never used again.  But better than a hammer job.  First I would be checking accurately, and I mean accurately, the dimensions of these interfefence-fit parts and, of course, referring to the linear coefficients of expansion for the materials to see what delta T would be required.

I presume they would be jig-fitted at manufacture, for alignment, however they may have been persuaded onto the shaft.  Once jig is adjusted, it would be fixed and correct forever (hopefully).  I would doubt they are hammered on, pressed maybe, but almost certainly with some differential temperature assistance.

Regards, RAB

Regards, RAB

[XYZER]

I would get it in correct timing rotation and drive it on
I would respectfully disagree. I would not just drive it on unless as a last resort.

I bet $100.00 Dursely or the Indians didn't put the crank in a freezer and heat the gear......of course that is my opinion.....and either way will work but most important is the rotation......

[mobile_bob]

heat and fit gears are very common in my industry, over the years many engine manufacture used the method
for various parts,

cummins heated cam gear and slipped them onto the end of the cams, and still do on most all of there engines

all sorts of heavy gear case gears are heated and slipped on as well.

the last thing you wanna do is press on a gear and have it gall up and provide a lump that will end in a cracked gear

i have heated an aweful lot of gears in the last 35 plus years and have them slip right into place, cool and lock
down tighter than the hubs of hell.

personally i would not recommend any other method, even though i am sure other methods might work some of the time
and by work i mean work for the life of the engine.

there is a reason the original gear broke, could be from earlier cam gear failures, or just as likely it was because the oem gear
was beaten into place by a gorilla in sandles with a sledge hammer.

beat on the crank and you may very well bend it?  press it unsupported properly and you will likely bend the crank? any stress likely
will end up as a problem in the fillet area, and maybe it becomes a broken crank later?

we can look to the oem lister for how they did it, but
can we really?

we assume the fit spec's are the same? a big assumption
we assume the metallurgy is the same? another big assumption

take the new gear and see if you can "touch" it with a file, my bet is it isn't hard at all
if it is then you gotta be careful as to how much heat to put on it,
if it files easy then it is not harden at all, and can be heated to 600-650 degree's with no
detrimental effects

heat it, drop and turn to position,
work fast and work clean

put a soap stone witness mark where you want the valley of the gear teeth to land
and do the deed

bob g

[vdubnut62]

One of these days maybe I'll learn to keep quiet around people that know more than I do!
Ron