ACCESSORY OF THE DAY 12/30/09 DUNN CRANKSHAFT COUNTERBALANCE WEIGHTS

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Model T Ford Forum: Forum 2009: ACCESSORY OF THE DAY 12/30/09 DUNN CRANKSHAFT COUNTERBALANCE WEIGHTS
Top of pagePrevious messageNext messageBottom of page Link to this message  By Jay - In Northern Ca. on Wednesday, December 30, 2009 - 02:39 pm:

Here's a set of original accessory counter balance weights for smoothing out the engine.
dunn3 dunn4
dunn1 dunn


Top of pagePrevious messageNext messageBottom of page Link to this message  By Seth Harbuck - Shreveport, LA on Wednesday, December 30, 2009 - 03:01 pm:

For the record, "smoothing out the engine" is not what they do.

What they do is reduce crankshaft and main bearing stress by counteracting some of the reciprocating mass of the pistons. This has the benefit of reducing wear on the center (second) main bearing.

But, the Dunns are an inferior way to add counterbalance since they are bolted between 1&2 and 3&4 and require far greater mass to do the same job as the "correct" way to counterbalance such as the Suremike crankshaft where the counterweights are outboard of 1&2 and 3&4 - next to the main bearings.

A balanced stock T engine with correct bearing clearances will be just as smooth as one with Dunn counterbalance weights fitted.

Seth


Top of pagePrevious messageNext messageBottom of page Link to this message  By Paul Vitko on Wednesday, December 30, 2009 - 03:42 pm:

A bitch to do a good job of installing.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Stan Howe on Wednesday, December 30, 2009 - 03:44 pm:

All that theory might be fine but a engine with them in sure runs smoother.


Top of pagePrevious messageNext messageBottom of page Link to this message  By A,J, Bell on Wednesday, December 30, 2009 - 03:56 pm:

Hi All

Dunn was issued two patents for
“Engine-Shaft or “Crank Shaft” Counterbalance
that did not refer specifically to Ford engines,
but used “numerous types of engines” or
“internal combustion engines” in his descriptions.

Both patents are listed below.

William G. Dunn
Patent number: 1248832
Filing date: Jun 21, 1917
Issue date: Dec 4, 1917
http://tinyurl.com/ybwsdd8

William G. Dunn
Patent number: 1259086
Filing date: Dec 17, 1917
Issue date: Mar 12, 1918
http://tinyurl.com/yeg7wnd


Regards
Art


Top of pagePrevious messageNext messageBottom of page Link to this message  By Les Schubert on Wednesday, December 30, 2009 - 03:58 pm:

I agree with Paul. I have had them on my '27 for about 30 years.
I bet I spent more than a day hand fitting them. Then I had the whole mess spin balanced. Balanced the flywheel independently.
I wonder if the originals were easier to put on?
Certainly Seth is right about the location of the weights.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Wayne Sheldon on Wednesday, December 30, 2009 - 08:11 pm:

I wish to regale a tale of woe! More years ago than I care to admit, a good friend had a set of these on a 'T' speedster he had bought. He, I and a fair number of others active with 'T' speedsters had just run the "Calistoga Classic" dirt track race re-enactment. He was home, cleaning up the car, making minor repairs and tuning it up real nice. Standing beside the car, he gunned the engine to a resounding crash with objects flying all about. one side of the pan was laid out near flat, while about half the lower block on the other side was scattered across the driveway. The most frightening thing was the sizable dent in his chain-link fence, 30 feet away.
TO BE FAIR! After he checked things out, he reported that whomever had installed the Dunn weights used standard soft bolts one size too small. Proper bolts would probably never do that and I would not hesitate to use a set if I had them. But I will never forget the sight of that busted up engine, and it still ran well.
W2


Top of pagePrevious messageNext messageBottom of page Link to this message  By Paul Vitko on Wednesday, December 30, 2009 - 09:52 pm:

Seth and I fiddled with one peace counterweights that would take less bolts to hold and less pressing on a weak crank web distorting it but the best way is with weight on each side opposite the rod journal.

Testing cranks I have found out that the T crank is weaker in all the tests with the with the throws vertical and strongest with the throws horizontal, I don't know if this is because of the constant change of direction of the cast iron slugs weakening the crank over time or if it was made that way, but counter balance would help the weak stock crank. The interesting thing is if a crank is bent its always bent with the throws vertical.


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Danuser on Thursday, December 31, 2009 - 11:28 am:

If anyone needs a set of these counter weights I have a set, minus a couple of the bolts, new never installed 70.00 plus UPS danuser88@socket.net


Top of pagePrevious messageNext messageBottom of page Link to this message  By Fred E HoustonD on Thursday, December 31, 2009 - 01:16 pm:

I installed a set of these at full weight, modified for a 26-27 crank, bedded in devcon, then spin balance, smoothest stock crank Ive ever run. I now regret that I removed them to do some experimenting with lighter weights.

They will go back in next time I have the engine out.

Drove to the top of Mt Evans with 10 tooth pinion. Only got out of high 2 times. Never used the Ruckstell. I believe that had I been trying, I could have pulled it in high.

These counterweights are designed for the early crank and require the devcon bedding to keep crank straight. I have no experience with using them on the early crank.

Car has 12 V battery on running board and is charged with a Seth Harbuck regulated magneto charger.

P1

P2

P3

P4


Top of pagePrevious messageNext messageBottom of page Link to this message  By Paul Vitko on Thursday, December 31, 2009 - 01:36 pm:

One beautiful T Fred! The similar 16 I am fiddling with will be "Old Ugly" left stock.

Interesting that the heavy weights work better.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Stan Howe on Thursday, December 31, 2009 - 02:19 pm:

There is a lot of difference in the original weights and the later reproductions. The originals were designed for the diamond shaped cranks and actually bolt on quite well. They had special bolts and were apparently quite well liked by a lot of people in the day, as Dunn sold about a zillion sets of them.

I loaned my mint original set to Fred several years ago for him to copy and do some testing with.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jay - In Northern Ca. on Thursday, December 31, 2009 - 02:23 pm:

Does anyone know where I can get a new set of correct bolts for these originals?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Stan Howe on Thursday, December 31, 2009 - 03:57 pm:

AFAIK those are the correct bolts. I'll try to remember to take a picture of mine and post it. The originals have those little pins in them to keep them from turning when you tighten the nuts.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Fred E HoustonD on Thursday, December 31, 2009 - 07:56 pm:

We don't use the original bolts. We use grade 8 bolts and lock nuts torqued to about 50 lbs. We keep a dial indicator on the crank to make sure the crank does not bend.


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