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Author Topic: Oliver Tiger MK IV - Compression Screw Thread Details  (Read 258 times)
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Jez Wilkins
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« on: April 28, 2019, 08:14:33 AM »

Hi all.

I am trying to find out the details of the thread of the compression ‘screw’ of the Oliver Tiger MK IV engine [i.e., thread diameter, threads per inch and thread form].  I need this information, as I want to replace the ‘T(ommy) bar’ screw currently in place, for a ‘grub’ screw [or socket head cap screw], so that I can use the engine in a control line team race event.

This site http://www.modelenginenews.org/restored/ollie_cub.html gives details for the Oliver Tiger Cub as ¼ - 32 ‘Model Engineer’ [ME], which is, apparently, a glow plug thread, apart from having a different thread angle (ME 55 degrees, glow plug 60 degrees).

I have tried my Tiger MK IV‘s compression screw in the head of a Super Tigre G15 and, whilst it does fit, it is too tight to turn.  A glow plug will, however, insert (and turn) into the head of the Tiger MK IV.  Must confess, that I don’t know enough about thread forms, to know if these results indicate that the thread form of the Tiger head is 55 or 60 degrees. Embarrassed

My next question is, does anybody know of a UK source of suitable ‘grub’ [or socket head cap] screws to fit the Tiger head, whatever the thread details turn out to be?  The screw length needs to be ½’’ (or, say, 15mm).

The serial number on the lug of my Tiger is ‘T8102’, just in case this might be of relevance.

Thanks very much, in advance.

Jez Wilkins
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OZPAF
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« Reply #1 on: April 29, 2019, 09:46:41 PM »

Jez have you approached Barton CL Forum?

http://controlline.org.uk/Barton/index.htm

John
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Jez Wilkins
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« Reply #2 on: April 30, 2019, 05:11:56 AM »

Jez have you approached Barton CL Forum?

http://controlline.org.uk/Barton/index.htm

John

Hi John and thanks very much for the reply.

I was a member on the Barton Forum website for many years, but left around four years ago, following some posts made by a couple of members on there, just after our (UK) 2015 General Election.

If nobody on here knows the answer, then I have maybe a couple of other alternative sources to try for the information/screw.  Our (UK) CL contest season is coming up, for one thing, so I may be able to get something sorted out at one of the race meetings.   

Failing that, I will probably have to try to neatly remove the 'T' from the current 'T(ommy) bar screw and use the remainder and a  suitably sized allen key (or similar) to make the compression adjustments.  Not my preferred method, as I will then probably be unable to return the engine to its original state, if I one day want to sell it on, but there you go. Smiley

Cheers,

Jez Wilkins 
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billdennis747
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« Reply #3 on: April 30, 2019, 05:31:51 AM »




Failing that, I will probably have to try to neatly remove the 'T' from the current 'T(ommy) bar screw and use the remainder and a  suitably sized allen key (or similar) to make the compression adjustments. 
I certainly wouldn´t do that! Somebody like Gordon Cornell will know
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Fourfingers
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« Reply #4 on: April 30, 2019, 05:03:41 PM »

Boltbase on eBay sell most sizes of cap heads, sockets and Allen screws.  If your MK Iv is a Ridley, he might have gone metric.  I'll check mine tomorrow when its light!
john
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Fourfingers
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« Reply #5 on: April 30, 2019, 05:05:51 PM »

PS re Barton .... here is definitely more relaxed!
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Jez Wilkins
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« Reply #6 on: May 01, 2019, 04:52:44 AM »




Failing that, I will probably have to try to neatly remove the 'T' from the current 'T(ommy) bar screw and use the remainder and a  suitably sized allen key (or similar) to make the compression adjustments. 
I certainly wouldn´t do that! Somebody like Gordon Cornell will know

Thanks for the 'heads up', Bill.  Removing the 'T' is not an elegant solution, I know - but I've seen it done by others in the past. Smiley  Would also mean the difficulty/expense of purchasing a replacement 'T(ommy) bar', if you wanted to return the engine to 'showroom condition', as it were, at some later date.


Boltbase on eBay sell most sizes of cap heads, sockets and Allen screws.  If your MK Iv is a Ridley, he might have gone metric.  I'll check mine tomorrow when its light!
john

Thanks for the information, Fourfingers/john. I'll have a look at Boltbase.  My MK IV is definitely not a 'Ridley' one.  I did wonder about Clint Hill Engineering as a source of a suitable 'grub' screw - my understanding was that Tom Ridley was trying to be as 'authentic' as possible - but, must confess, that I don't know whether or not that extended to the fastenings.  I know that Oliver production has ceased, at least temporarily, following Tom's death, but wondered if they might have some spares, still on the shelf.  Had a bit of trouble trying to find a telephone number for Clint Hill Engineering, but did eventually find one, which I have not yet had the opportunity to try, to see if it is still current.

PS re Barton .... here is definitely more relaxed!

I chose my words carefully, in response to OZPAF/John's post about the contacting the Barton CL Forum, so am going to keep 'diplomatic silence', from now on, in regard to said site. Smiley

Cheers,

Jez Wilkins     
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Fourfingers
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« Reply #7 on: May 01, 2019, 05:45:20 AM »

Jez, Clinthill v quiet, understandably.  Flair(or Flare) models seem to have an ear to the ground on this.  Find them on t'internet.
Now the sun has risen I can do some measurements ....
Data for, inorder, diam of threaded screw, lenght and number of threads, threads per mm:
JS MK III T5659.  6.26, 6.0/8, 1.33
TR MKIV T8993.   6.35, 8.31/11, 1.32.
Each comp screw fits the other.  Diameters might be my measuring error!
Also I have two schnozzle Cubs, both late manufacture from JSO and TR.  Comp screwdefinitely NOT interchangable.
Just going to rummage in rubbish drawer, must be a cap head somewhere to fit.
Laters
john
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Fourfingers
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« Reply #8 on: May 01, 2019, 05:58:30 AM »

No luck, I'm afraid.
One last thought .....
The amazing collection of David Owen' engines and spares still continues on evilbay.  Heave 111 is the seller, and a regular guy, no doubt.  Last week a lot was Oliver Tiger bits and bobs.  Worth an email?  Postage 10 to15 £ perhaps.
Closer to home, Yakolev on the dreaded Bay may have some Olly bits.  Also worth a try.
Good luck
john
Or, as a mate once said when we couldnt find a kennel for the dog during hols, "shoot the dog, get a new one when you come back".  Sorry.
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Footloose
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« Reply #9 on: May 02, 2019, 04:08:00 AM »

I have measured one of my MKIII motors, I can’t remember where my MKIV motors are, and my tired eyes make it 1/4 x 32 which may be an ME thread for which you won’t get a cap head screw but a UNS 1/4 x 32 would probably fit.

Bert
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Jez Wilkins
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« Reply #10 on: May 02, 2019, 05:21:52 AM »


Jez, Clinthill v quiet, understandably.  Flair(or Flare) models seem to have an ear to the ground on this.  Find them on t'internet.
Now the sun has risen I can do some measurements ....
Data for, in order, diam of threaded screw, length and number of threads, threads per mm:
JS MK III T5659.  6.26, 6.0/8, 1.33
TR MKIV T8993.   6.35, 8.31/11, 1.32.
Each comp screw fits the other.  Diameters might be my measuring error!
Also I have two schnozzle Cubs, both late manufacture from JSO and TR.  Comp screwdefinitely NOT interchangable.
Just going to rummage in rubbish drawer, must be a cap head somewhere to fit.
Laters
john
No luck, I'm afraid.
One last thought .....
The amazing collection of David Owen' engines and spares still continues on evilbay.  Heave 111 is the seller, and a regular guy, no doubt.  Last week a lot was Oliver Tiger bits and bobs.  Worth an email?  Postage 10 to15 £ perhaps.
Closer to home, Yakolev on the dreaded Bay may have some Olly bits.  Also worth a try.
Good luck
john
Or, as a mate once said when we couldn't find a kennel for the dog during hols, "shoot the dog, get a new one when you come back".  Sorry.

Hi again Fourfingers/John.

Thanks very much for the 'heads up' about Flair, Heave 111 and Yakolev. I will have a look at these.

Your measurements for your MK III and IV come up not much different to 1/4 x 32 x 32 t.p.i., don't they, when converted to imperial? Smiley  One 'original' and one new manufacture. Hmmn. According to the website that I referenced in my initial post, the Oli Cub was definitely 1/4 x 32 ME, but maybe your late manufacture 'schnozzle' ones aren't? Hmmn.  Thanks for looking for a suitable cap head.  Smiley  I could use a MK III copy (CS), but really want to use the original MK IV, if I can. Smiley

I have measured one of my MKIII motors, I can’t remember where my MKIV motors are, and my tired eyes make it 1/4 x 32 which may be an ME thread for which you won’t get a cap head screw but a UNS 1/4 x 32 would probably fit.

Bert

Hi Footloose/Bert and thanks very much for the measurement/information and post.  I was not familiar with the 'UNS' designation (have come across 'UNC' = 'Unified Coarse' and 'UNF' = 'Unified Fine' before, though).  'UNS' = 'Unified Special' as per this webpage https://www.threadcheck.com/technical-documents/thread-systems.pdf.  Am going to assume that this is the correct designation for 'UNS', unless you (or someone else on here) posts to tell me any different. Grin 

Cheers,

Jez Wilkins   

 
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Footloose
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« Reply #11 on: May 02, 2019, 06:17:13 AM »

Jez

It’s also designated as NEF “national extra fine” it’s similar to the normal glow plug thread.

Bert
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Jez Wilkins
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« Reply #12 on: May 03, 2019, 08:10:21 AM »

Jez

It’s also designated as NEF “national extra fine”

Hi again Footloose/Bert.  I had wondered if 'UNS' was just a different nomenclature for 'UNEF' and thanks very much for clarifying that this is the case.

it’s similar to the normal glow plug thread.

My understanding, from this website http://www.modelenginenews.org/restored/ollie_cub.html and again here https://trfastenings.com/Products/knowledgebase/Thread-Geometry/Unified-Extra-Fine-UNEF is that 1/4 x 32 UNEF is the glow plug thread, with the thread angle of 60 degrees, only differing from 1/4 x 32  Model Engineer in 5 degrees of thread angle (55 degrees for ME).

Thanks, once again, for the reply. Smiley

Cheers,

Jez Wilkins   

 
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qazimoto
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« Reply #13 on: May 21, 2019, 10:50:51 PM »

Jez,

the Original Olivers were BA I believe, but the ones with your serial were 1/4" 32 ME (Model Engineer as you say). The Rothwells are 1/4"  32 TPI UNEF, the glow plug thread.

I have quite a collection of Olivers and their clones. I've used the Rothwell replacements in Olivers with zero problems. The R250 comp screws are generally made of Brass and arn't fully cut to keep them tight in the cylinder fin assembly. If you contact Steve Rothwell he should be able to supply socket head and traditional style at a good price.
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Jez Wilkins
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« Reply #14 on: May 22, 2019, 06:17:34 AM »

Hi qazimoto.

Thanks very much for the reply and information.  I was at the 'Barton Bash' over the weekend and the 'gen' there also was that 1/4" x 32tpi ME is the thread.  So, at least I know what I'm looking for now - thanks all. Smiley  I'll see, in the first instance, if I can find a UK source for a UNEF version and if not, it looks like I'm 'Aussie bound'.  Grin

Cheers,

Jez Wilkins   

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