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#Post#: 7458--------------------------------------------------
Making A Twin
By: 660magnum Date: February 11, 2012, 3:28 pm
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I have a automotive machine shop friend in Idaho who flies model
airplanes. He also sometimes makes up engines using parts of
existing engines with custom crankcases, changing from piston
ported to reed valve etc. He also converts glow fueled engines
to ignition running gasoline with custom sensor and Walbro carb
mounts and manifolds.
After making a couple 50 and 55cc reed valve singles, his latest
project is a 60cc twin using existing available 30cc single
parts.
Here is the engine partially assembled
[img]
HTML http://img.photobucket.com/albums/v11/jamesirl/Lj23708.jpg?t=1328724306[/img]
He has purchased mufflers made by another gentleman
[img]
HTML http://img.photobucket.com/albums/v11/jamesirl/Ro41583.jpg?t=1328994565[/img]
The drive hub, reed pyramid assembly, and carb are from existing
available parts.
[img]
HTML http://img.photobucket.com/albums/v11/jamesirl/Hd94944.jpg?t=1328994582[/img]
He has made the crankcase and adapted some of the purchased
parts.
[img]
HTML http://img.photobucket.com/albums/v11/jamesirl/Fk16813.jpg?t=1328994599[/img]
#Post#: 7459--------------------------------------------------
Re: Making A Twin
By: 660magnum Date: February 11, 2012, 3:37 pm
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He made the crankshaft from two existing 30cc cranks. The rear
one is another front one that is cut off at the back bearing. He
pushed the crank pins out, made a round center disk, and pushed
in new hardened crank pins with the rods attached to make the
twin crankshaft assembly.
[img]
HTML http://img.photobucket.com/albums/v11/jamesirl/Ge95698.jpg?t=1328994635[/img]
Here is a view of the original crank assembly
[img]
HTML http://img.photobucket.com/albums/v11/jamesirl/ldleg3002.jpg?t=1328994713[/img]
The purchased piston for the 30cc engine
[img]
HTML http://img.photobucket.com/albums/v11/jamesirl/ldleg3004.jpg?t=1328994793[/img]
The purchased cylinder
[img]
HTML http://img.photobucket.com/albums/v11/jamesirl/ldleg3001.jpg?t=1328994832[/img]
#Post#: 7460--------------------------------------------------
Re: Making A Twin
By: 660magnum Date: February 11, 2012, 3:50 pm
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The cylinders and cranks are $40 ea
The pistons are $10ea and the rings are $5ea
The drive hub is $16
Main bearings were $30 for all three
The needle bearings for the wrist pins were $3 ea
The carb $40 and reed block $15
That comes out around $300 and then you have the aluminum block
for the crankcase and black plate and the steel plate for the
crankshaft joiner. And a lot of labor and amortization of
machines and shop space.
This gentleman has saved some twisted crankshafts for me by
re-aligning them.
#Post#: 7478--------------------------------------------------
Re: Making A Twin
By: 660magnum Date: February 11, 2012, 8:10 pm
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These cylinders use NGK CM-6 (Honda generator) spark plugs.
The complete ignition system including the spark plugs would be
about $75
Then you will need a $25 battery, a $12 switch and wiring
harness, and a battery charger for the ignition.
#Post#: 7479--------------------------------------------------
Re: Making A Twin
By: Chainsawrepair Date: February 11, 2012, 8:16 pm
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Is that the twin that you had over here? Maybe you didnt have a
twin and my memory is just that bad. :P
#Post#: 7481--------------------------------------------------
Re: Making A Twin
By: 660magnum Date: February 11, 2012, 9:07 pm
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The twin that I have (and I don't think I brought it over to
your house - I mentioned it) is made from two Dolmar 111/115
cylinder/piston assemblies.
Remind me the next time I come over and I can bring it and the
single.
They were manufactured by a small outfit called Brison. The
single I have has never been run.
Brison 3.2 single and 6.4 twin
#Post#: 7510--------------------------------------------------
Re: Making A Twin
By: Al Smith Date: February 12, 2012, 6:39 pm
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Off all the proceedure in my opinion aligning the crankshft
would be the most difficult part .
On a Harley crank it's relatively simple .You just chuck it
between centers in a lathe and use dial indicaters and wedges
and c-clamps and tighten up the pin nuts .
With a hard pressed crank you'd about have to have each section
perfect I would think before you pressed it .I've never seen it
done so I have no idea how they do it .Just seems like a bear to
me .
#Post#: 7528--------------------------------------------------
Re: Making A Twin
By: 660magnum Date: February 13, 2012, 8:28 am
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I received a note from Richard about the engine that it is . . .
. "now polished and painted and finished assembled. So far so
good. I will hopfully get the rest of my parts in this next
week. Oh The hub is a one of a kind deal since I will be
swinging larger props I used the 55 hub size and bolt pattern,
then necked it down to the 30 to match the case size. The
retaining nut I made from a grade 8 bolt and I will never do
that again, darn thing ruined a brand new made in the USA Tap a
very spendy tap at that *L* "
(He was talking about ruining his new tap while making the
barrel nut that holds the prop drive hub onto the crankshaft)
#Post#: 7547--------------------------------------------------
Re: Making A Twin
By: Cyberwolf Date: February 14, 2012, 11:32 am
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Hello I am Jims friend in Idaho that is making this engine, Jim
asked me about how to realign crankshafts.
I thought I would post this here for all to see.
There are a couple of ways that I know of depending on just how
badly tweeked they are tells me which way I want to start.
The first is to use a Milling Machine vise and clamp the
counterweigths together to pull them back inline with each
other, If the counterweigths are machined round on the rod end
when the counterweigth was turned, I clamp them in several
places then check with the following method. Sometimes this can
work well and little or no other tweeking is needed. This does
take a good vice with hardened jaws to do this job.
The other is to put the crank between dead centers in a Lathe
and check the run out with an indicator, then decide which way
it needs to be moved, then take a brass drift and hammer and tap
the counter weight, fairly hard to align the crank back within
specs. This takes some practice and some are very hard to move.
Just remove the dail indicator before you start wailing away or
you will be buying a new one.
I try to get mine within .0005 or less but there are times they
just won't come in any closer than .001 Which is well within
specs. Myself I just want them as close as possible for less
chance of vibrations and out of balance conditions.
All of these things rob HP and torque. If any one need father
info or has questions please feel free to ask.
Richard.
#Post#: 7548--------------------------------------------------
Re: Making A Twin
By: Chainsawrepair Date: February 14, 2012, 12:27 pm
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[quote author=Cyberwolf link=topic=741.msg7547#msg7547
date=1329240759]
Hello I am Jims friend in Idaho that is making this engine, Jim
asked me about how to realign crankshafts.
I thought I would post this here for all to see.
Richard.
[/quote]
Welcome and Thanks for sharing info here.
You dont have to worry about me taking any crankshafts apart.
But you never know about some of these other guys.
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