Australian Olympic vs British Seagull AD102

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AusAnzani
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Re: Australian Olympic vs British Seagull AD102

Post by AusAnzani » Wed Mar 20, 2019 1:52 am

Bruce, thanks for providing link to the vid and discussing heights yesterday. I had seen the picture but it did not register fully.

Below are photos I have taken showing the difference in exhaust and drive tube lengths ie Olympic # 103 and # 276 (same) against BS AD 102 standard. The BS tube and drive shafts are the longer.
IMG_6915_R.jpg
IMG_6924_R.jpg
I wonder if the exhaust tube on your longer Olympic measure the same as the standard 102 exhaust tube? Are you able to compare/measure please?

Thanks & regards,
Spiro
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Re: Australian Olympic vs British Seagull AD102

Post by AusAnzani » Wed Mar 20, 2019 2:29 am

Charles uk wrote:Before you go anywhere near that ring with a file.

Gap it again when it's in the right location, 5 mm above the exhaust port, push it into that position with the skirt of a piston, to ensure squareness.

Measure again.

The previous position was good enough to show that the bore diameters were different.
Agreed Charles, the previous photos were to show there was a difference only. Now a question for you. Have you seen this type of piston ring (Square ends) and ring pin (centrally located in the groove - and extending to the outer perimeter of the piston) arrangement before? What is the gapping procedure?

Here are some more pics. Piston ring and pin arrangments on Olympics # 103 & #276 are the same. I have attempted to drive the pins in further to allow filing of the ring so it sits over the top (per image below) but they wont budge. There is no through hole as such into the internal of the piston, just a solid piece of casting to secure the pin.
Capture.JPG
Photos the real things lol

Piston from Olympic # 276
IMG_6937_R.jpg
Piston from Olympic # 103
IMG_6938_R.jpg
Piston internal casting - same on both # 103 & # 276
IMG_6951_R.jpg
So we have 4 rings and 4 pins that are identical in every respect.

Clearly, the reason the ring gap must be larger than normal (and possibly still too large due to wear) is because it needs to allow for the centrally pin which is centrally located in the groove. Hence the correct gap may be the sum total of typical gap for 2" piston (in water-cooled engine) and pin diameter.

These outboards were obviously in use, so the piston ring and pin design works. If the rings had sat over the pins and the end sections had broken away, there would be signs of scoring in the cylinder and piston of which there is none.

Although I am certain I have seen this arrangement previously, I am at a loss now to find anything in my files or on the internet that shows and discusses it.

Your comments would be appreciated.

Regards,
Spiro
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Re: Australian Olympic vs British Seagull AD102

Post by Charles uk » Wed Mar 20, 2019 3:09 am

Ring pin in exactly the same position as a Seagull piston, half in half out of the groove.

Only markings inside the oversize piston A 1 4 smaller ring pin lumps. bare weight 128.4 grams
Seagull new piston bare weight 124.3 grams DINAMIN 766
Other seagull pistons AE 16743, HEPOLITE & a load of numbers

Connect your Olympic piston to a Seagull by putting a single gudgeon pin in both pistons, if both skirts sit level on a surface plate or a very flat surface then the inlet timing is identical if it is, separate them still on the flat surface & compare the transfer side & the exhaust side to compare those timings.

The oversize & the new Seagull pistons have identical port timings within manufacturing tolerances.

I've only seen the hidden pin style on 4 strokes with low height but much deeper rings

I asked about the bridged exhaust as you had caps on both ends of the gudgeon pin I assumed it was a floating pin & you wouldn't want it to fall down the exhaust port.
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Re: Australian Olympic vs British Seagull AD102

Post by AusAnzani » Wed Mar 20, 2019 6:39 am

Charles uk wrote:Ring pin in exactly the same position as a Seagull piston, half in half out of the groove.
Could be from a Villiers Midget or any number of other engines as that profile was not uncommon.
Charles uk wrote:Connect your Olympic piston to a Seagull by putting a single gudgeon pin in both pistons, if both skirts sit level on a surface plate or a very flat surface then the inlet timing is identical if it is, separate them still on the flat surface & compare the transfer side & the exhaust side to compare those timings.

The oversize & the new Seagull pistons have identical port timings within manufacturing tolerances.
I'm all Olympic'd out for the moment lol. Will leave it till the weekend.
Charles uk wrote:I've only seen the hidden pin style on 4 strokes with low height but much deeper rings
Makes sense.
Charles uk wrote:I asked about the bridged exhaust as you had caps on both ends of the gudgeon pin I assumed it was a floating pin & you wouldn't want it to fall down the exhaust port.
Appreciate the concern lol.

As for ring gap sizes, what is typical for an unused Seagull 102?

Searching the net, I found this guide by a ring manufacturer, Wiesco I think it was.

A rule of thumb for ring end gap measurement is to use the bore size in inches x .005”. In the example here, a KTM150, the bore is 56mm (56 divided by 25.4 = 2.2047”). If you multiply 2.2047” x .005”, the result is .011”. This would be the minimum installed ring end gap. A typical high measurement for the piston ring end gap would be the bore in inches x .007” (2.2047 x .007” = .015”). These calculations are a general guideline, and your OEM service manual will also provide further detail.

How does that stack up?

Also, what are your thoughts to gapping the rings on the Olympic. I am thinking it should be the sum of ring pin diameter plus the standard Seagull gap. Does this sound about right to you?

Thanks & regards,

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Re: Australian Olympic vs British Seagull AD102

Post by Collector Inspector » Wed Mar 20, 2019 8:29 am

Having some problems in locating what parts were returned from Steve.........I found this though.

The Clamps are bright plated.....

20190320_152314_HDR[1].jpg
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Re: Australian Olympic vs British Seagull AD102

Post by Collector Inspector » Wed Mar 20, 2019 9:34 am

This was a mission to find and extract from under a heap of heavy and sharp projections commonly found on Old Dears......it was outside under a woodworking bench....protected from weather but not dust and critters....found an early Evinrude 5524 that was just waiting for a head gasket as well (12 years and counting).

Number 304

Seagull bracket.

Early gearbox.....no cav plate.

I can not find any previous pics of this one? No idea!

I will pull it apart on the weekend so as to have another box of Old Dear Fragmentation.

:lol:

20190320_160142_HDR.jpg
20190320_160024_HDR.jpg
20190320_155245_HDR.jpg
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Re: Australian Olympic vs British Seagull AD102

Post by Collector Inspector » Wed Mar 20, 2019 10:41 am

OK another One.....the black and blinged up one.......

It is 386.

Interesting that the stamping is different and on the starboard side as compared to 304 on the port side.

20190320_171414.jpg
Add to the mix S.

Regards

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Re: Australian Olympic vs British Seagull AD102

Post by AusAnzani » Fri Mar 22, 2019 1:53 am

Hello B, thanks for sharing. More useful information indeed.

Sorry also for the delayed response!

Looks like you have them breeding over there again lol.

A few observations from your vid also:

1. Your blinged unit is fitted with a raked SD style propeller, which is not original. Also, the dimples on the tank end, I have not seen another Olympic like that. Edit: Via the Search facility I found previous comments, tank not original, modified fire extinguisher lol.
2. The image of your short and long Olympics together, interesting to note that both have pump housings with cavitation plate. Both are therefore more recent builds, like your Tiller.
3. Images of Tiller in your kitchen further confirm it is without serial / build number.
4. One of your fuel tanks shows black paint over green. This gives me hope that the tank on # 103 will be same, thus allowing me to color match locally.

Bruce, look also here; viewtopic.php?f=17&t=5305&p=44733&hilit=olympic#p44733 You will see your Olympic # 447 with Seagull Conrod. Piston looks to have same rings as those pictured above, hence is likely to have the centrally located round stop pin as well.

As always, i would love to be able to search your sheds for parts lol. You have a gold mine over there my friend!

Regards,
S
Last edited by AusAnzani on Fri Mar 22, 2019 2:29 am, edited 2 times in total.

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Re: Australian Olympic vs British Seagull AD102

Post by AusAnzani » Fri Mar 22, 2019 2:02 am

Sorry - deleted duplication

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Re: Australian Olympic vs British Seagull AD102

Post by Charles uk » Fri Mar 22, 2019 7:06 am

I don't have pictures of a Montessa but from memory the tank has 4 dimples on each end like some plastic bottles.

do you have a pic of tank?
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Re: Australian Olympic vs British Seagull AD102

Post by Collector Inspector » Fri Mar 22, 2019 7:49 am

Charles uk wrote:I don't have pictures of a Montessa but from memory the tank has 4 dimples on each end like some plastic bottles.

do you have a pic of tank?

The tank with the dimples is or was a small fire extinguisher. The cap and the up-threads are original.

Dimples are one end only and the release valve hole has been welded over on the other end.

I have a spare tank to change it out later.

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Re: Australian Olympic vs British Seagull AD102

Post by Collector Inspector » Fri Mar 22, 2019 7:52 am

Thanks for that link S!

I have added those pics that Steve sent me below. They should be here I think.

IMG_0007.jpg
IMG_0006.jpg
IMG_0005.jpg
IMG_0003.jpg
IMG_0001.jpg
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Re: Australian Olympic vs British Seagull AD102

Post by Collector Inspector » Fri Mar 22, 2019 10:51 am

Still no feedback as to your piston ring pins S?

Not really expecting any confirming as legit, as I said in our last call, the pin you have X 4 should be machined back within the land.

Why did Charles indicate above that your pics and initial Q, that your pins were 1/2 of the groove? Obviously not the case.

I will pull apart another one (mentioned earlier) this weekend to check if there are yet X 6 of them.

Music and Beers so Cheers for now

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Re: Australian Olympic vs British Seagull AD102

Post by Collector Inspector » Sat Mar 23, 2019 4:58 am

6 x 6 S!

304 has the same ring pins.

Con-rod as yours. Ugly but very sturdy.

Piston skirt is 2.2525"

Piston pin height = to BS.

Exhaust tube is exactly 15".

Exhaust port has a bridge.

BS style drive shaft. Fits over 0.37" square section.

Whitworth fasteners inc coarse threads.

They spared no cost saving measures with these. Hardware shop stock items. 8)

20190323_111956.jpg
20190323_111947.jpg
20190323_111935.jpg
20190323_111919.jpg
Crankcase and cylinder were silver frosted.

Gearbox/WP housing as well.

Cheers

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Re: Australian Olympic vs British Seagull AD102

Post by Charles uk » Sat Mar 23, 2019 9:13 am

Any manufacturers mark/logo inside piston? Bruce.
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