Sopwith Snipe Project

[brisfitworks]

Nick:

I think John is on the correct track - "Drill in Position" may be the key.

I have seen this with Camel and F2b dwg's. Stuff doesn't add up when you try to work from the dimensions, then you realize they "fitted", "drilled" or "position"'d on the job and the dimensin never mattered. It is very possibly they never noticed the mistake in the dwg office and no correction made because the stuff is assembled and jig drilled and only the jig dwg has the correction.

The fact that the two drawings use totally different refenences for the holes makes the error hard to spot.

I would guess that 9/16" radius that gets squared of by 1/16" was added twice for one part and subtracted twice for the other part by a draftsman and then we end up with a 1/4" error.

Real question is which dimension to trust!!!

I'm going through the Snipe microfilms I have, to look for your tank dwg's, I'll keep my eyes open for any helpfull clues!

I have interchangability tolerance sheets for the F2b and this has helped me with this sort of issues; a set for the Snipe would be a great help here!

Bill.

Originally Posted by Nick

Talking about drawing it sure would have been nice to have had the skills to do what Joe is doing with his Sopwith Baby project, and draw it all up in CAD first. Anything that doesn't quite add up then can be resolved before finding things don't fit
Here's an example. I'm in the process of making the centre section spars and have just noticed that there is a difference between the tie strap measurements and the spar of 1/4". On the Spar drawing the distance between the joint rod holes is 51" and yet on the Tie strap it is 51-1/4".

The drawing was done in April 1918 and has no signatures in the alteration section but has a note at the bottom along the line of "to original blueprint 8th Oct 1921".

Snipes were used right through to 1927 so occasionally parts were modified but annotated in the Alteration column.
So unless there's a reason I'm missing (as usual) why the difference I'm not sure which dimension is correct.

Nick

[NostalgAire]

Bill (brisfitworks),

Email or call me please. I'd like to talk to you about the ternplate.

Scott
scott@nostalgaire.com
928-777-8195

[j ferguson]

Originally Posted by brisfitworks

Nick:


The fact that the two drawings use totally different refenences for the holes makes the error hard to spot.

I would guess that 9/16" radius that gets squared of by 1/16" was added twice for one part and subtracted twice for the other part by a draftsman and then we end up with a 1/4" error.

Real question is which dimension to trust!!!


Bill.

After looking at this some more, I think there are actually no hole location dimensions on the upper drawing therefore no conflict. the lower drawing locates the pivot rod. I think you'll find the other hole locations on the bracket drawing. I agree with the other observtions about drilling in position - what a nightmare.

John

[Nick]

Originally Posted by brisfitworks

Nick:

I think John is on the correct track - "Drill in Position" may be the key.

I have seen this with Camel and F2b dwg's. Stuff doesn't add up when you try to work from the dimensions, then you realize they "fitted", "drilled" or "position"'d on the job and the dimensin never mattered. It is very possibly they never noticed the mistake in the dwg office and no correction made because the stuff is assembled and jig drilled and only the jig dwg has the correction.

The fact that the two drawings use totally different refenences for the holes makes the error hard to spot.

I would guess that 9/16" radius that gets squared of by 1/16" was added twice for one part and subtracted twice for the other part by a draftsman and then we end up with a 1/4" error.

Real question is which dimension to trust!!!

I'm going through the Snipe microfilms I have, to look for your tank dwg's, I'll keep my eyes open for any helpfull clues!

I have interchangability tolerance sheets for the F2b and this has helped me with this sort of issues; a set for the Snipe would be a great help here!

Bill.

Many thanks John and Bill for responding.

I'm inclined to agree that the squaring off of the 9/16" radius is the culprit for the error. I thought earlier that it may be because the earlier Snipe may have had a slightly different dimensioned centre section than the later one and the drawings were not matched. However I now think it was just an error. The location for the tie rod hole is specific even though it does say to be drilled in position, whereas the other holes do not show a measurement.
All of them are drilled once the joint box is fitted.
The plan showing the assembled Centre section also has the dimension between Joint rod centrelines as 51" so I'm going to stick with that
and then drill in position.
Interesting to hear you've seen this sort of thing before Bill. Have come across a few things that were either wrong or built differently to the plan but they haven't bothered to amend the plans. I guess the guys on the floor knew about it and that's what mattered.
It definately a great help to be able to crosscheck these things with as many sources as possible.

Thanks again to you both for your input

Cheers, Nick

[Nick]

The Snipe has a control grip very similar to the SE5a but with the addition of a blip switch.
I’ve had no luck in getting an original and don’t have the plans for it (listed as part # C2299) however I have the plans for the RAF grip (A14095) so have based it on that.
I made a grip and the levers out of wood and had them cast at a local foundry in aluminium and the levers out of gunmetal.
This is a grip that I photographed at the Imperial War museum in London. It was in a glass case so couldn’t get a side view of it.



These are the levers after casting, a wee bit of tidying up required! They are handed so I just made one with a lug either side to machine up later.





This is where it is at the moment. I just have to bore out the centre of the grip and cut the slot that goes around the inside of the ring and make up a switch. I’ll do that a bit later as would like to see a couple more photos of the original to make sure I’ve interpreted it correctly. Bill has very kindly offered to send me some so many thanks in advance.



Cheers, Nick

[tengew]

very nice nick
from the look of the one you took a pic of i think the trigger cross hatch filling were done in the field and not machined yours look great

when you say you cast them in gunmetal is that brass????
cant wait to see it fully machined and assembled

[Nick]

Originally Posted by tengew

very nice nick
from the look of the one you took a pic of i think the trigger cross hatch filling were done in the field and not machined yours look great

when you say you cast them in gunmetal is that brass????
cant wait to see it fully machined and assembled

Thanks Tengew,
I did the cross hatching with a file the same way they did.
The levers are made of gunmetal which is lead bronze.

Cheers, Nick

[brisfitworks]

Nick:

I have seen lots of this sort of confused stuff and I just found a bunch of errors in "A.P.810 Nov.1920 Spare Parts for Bristol F2b" @#$%^&*

I had many a person still in the aircraft industry laugh at how it is still the same today!

I descibed this before at length in Joe's Baby thread, so if your interested in some of the explanations of why the engineering office copies that we get don't reflect what we would call "as built drawings", try posts #265, #210, #208 and #204

Your last statement about "I guess the guys on the floor knew about it and that's what mattered." is the truest part of the issue of what we need to know to build these planes. Sometimes the only solution we have is try know their trades and put on their mindset and THEN look at the drawings again.

I did that with the fillet piece between top longeron and plywood turtledecking in the cockpit of the Camel. I knew what was on the drawing wouldn't work but still had to make progress - so I guessed. A couple years later I found a series of very clear photos and I had done almost exactly what was built as opposed to what was drawn!

Got to love this hobby - keeps you on your toes.

Cheers,
Bill.

P.S. and when the drawings and lack there of gets frustrating, I find that a couple pints of Guiness work very well

Originally Posted by Nick

.....
Interesting to hear you've seen this sort of thing before Bill. Have come across a few things that were either wrong or built differently to the plan but they haven't bothered to amend the plans. I guess the guys on the floor knew about it and that's what mattered.
....
Cheers, Nick

[brisfitworks]

Instead of sending, how about I just post them!
(I finally made some time and got a photobucket account)

This is an original our museum has.

Nick how do you plan to deal with the hollow chamber inside the ring?

The cross hatching on the triggers is cast in.

Note the blip switch pocket hidden by the cord.

(sorry about the large size, hard on your screen but good for details)

Originally Posted by Nick

... Bill has very kindly offered to send me some so many thanks in advance. ....Cheers, Nick

[Nick]

Originally Posted by brisfitworks

Instead of sending, how about I just post them!
(I finally made some time and got a photobucket account)

This is an original our museum has.

Nick how do you plan to deal with the hollow chamber inside the ring?

The cross hatching on the triggers is cast in.

Note the blip switch pocket hidden by the cord.

(sorry about the large size, hard on your screen but good for details)

Wow, thats great, many thanks Bill for posting those, thats incredibly helpful.
Thats really interesting to see that the levers are cast with that cross hatching. Thats different to the ones at the Imperial War museum which are filed at an angle. Would there have been different manufacturers for these?
As for the hollow chamber I plan on taking it down to trade school and either mounting it in a big 4 jaw chuck and boring it out or alternatively mounting it in a vice on a milling machine table. I'll then use a "T" slot cutter to cut the slot inside the ring.
I've got to finish off my fuel tank fittings first, then I'll do this.
Many thanks again Bill, you just made my day.

Cheers, Nick