Author Topic: Mk III Sport restoration  (Read 13311 times)

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Offline Dougiethenoo

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Mk III Sport restoration
« on: 10 Dec 2015 at 11:57 »
Hello, newcomer to the Douglas here,
I have acquired a 1948 Mk III Sport from "Vermont Ian" and am in the planning stages of a rolling restoration to the Sport configuration, with the over the top exhausts and single seat. I'd greatly appreciate some help in identifying measurements for mounting points for the exhuasts and for the seat.

Can anyone tel me the spring length for the standard single seat? Springs are available in various lengths and I can identify several different aftermarket saddles that can be bracketed at the front to fit - but the original rear seat spring length would be a good starting point, then I can make the front hinge bracket to suit.

Does anyone have a close-up picture of how the heat shields are mounted to the exhausts?

Any advice appreciated!

Offline douglas1947

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Re: Mk III Sport restoration
« Reply #1 on: 10 Dec 2015 at 16:16 »
I have used the large type replica single seats (Wassells) and changed the fixing points for the saddle springs to the frames (MK1 and MK5 were a little different in mesurement).
I used the original holes in front but made new brackets for the springs at the end of the saddle frame.
You can fix the saddle in the front lugs and will find the point for a new spring bracket.
I also have bought an other pair of springs, because the springs, comming with the saddle, were a bit ugly!

If it is a help for you, I will make a photo. The bikes are still in restauration!

Michael

Offline giz.neal

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Re: Mk III Sport restoration
« Reply #2 on: 11 Dec 2015 at 13:06 »
Dougiethenoo,

I've recently fitted a single saddle to my IIIS. My springs are 5" long and seem to fit well. They are available from Draganfly at Bungay in Suffolk, they come unchromed (possibly Ex WD?) but are otherwise good!

Steve

Offline eddie

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Re: Mk III Sport restoration
« Reply #3 on: 11 Dec 2015 at 14:06 »
Douggie,
              The exhaust pipes just have two 5/16"BSF nuts brazed on the side to take the short dome head heatshield bolts.
  If you are replacing the exhaust system, be aware that the Mk3 Sports silencers were quite a bit longer than the Mk4/5 silencers, so if you are going to have new pipes made and fit Mk5 silencers, it might be a good idea to make the pipes extra long so that they can be trimmed, when you have decided the best position for the silencers.
Regards,
               Eddie.
« Last Edit: 11 Dec 2015 at 14:14 by eddie »

Offline Doug

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Re: Mk III Sport restoration
« Reply #4 on: 30 Dec 2015 at 00:06 »
This is what the subframe mount for the rear of the Mark 3 Sports exhaust looks like. It bends out then down.





-Doug
« Last Edit: 30 Dec 2015 at 00:34 by Doug »

Offline Dougiethenoo

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Re: Mk III Sport restoration
« Reply #5 on: 08 Jan 2016 at 09:45 »
Thank you Doug, very helpful!

Offline Dougiethenoo

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Re: Mk III Sport restoration
« Reply #6 on: 08 Jan 2016 at 10:54 »
Douggie,
              The exhaust pipes just have two 5/16"BSF nuts brazed on the side to take the short dome head heatshield bolts.
  If you are replacing the exhaust system, be aware that the Mk3 Sports silencers were quite a bit longer than the Mk4/5 silencers, so if you are going to have new pipes made and fit Mk5 silencers, it might be a good idea to make the pipes extra long so that they can be trimmed, when you have decided the best position for the silencers.
Regards,
               Eddie.

Thanks for that. I plan to make replicas using 1" 3/8" OD 304SS tubing and weld captive nuts on. I'll be sure to measure up carefully against the existing underslung pipes and order extra tube.

Offline Dougiethenoo

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Re: Mk III Sport restoration
« Reply #7 on: 08 Jan 2016 at 11:04 »
Dougiethenoo,

I've recently fitted a single saddle to my IIIS. My springs are 5" long and seem to fit well. They are available from Draganfly at Bungay in Suffolk, they come unchromed (possibly Ex WD?) but are otherwise good!

Steve

Thanks Steve. I found a generic fit seat at Feked and bought 2 sets of springs for it - it comes with 4.5" that are tightly wound and I could extend at the top with spacers/bolts & locknuts - and I bought an additional pair of more loosely wound 6.5" springs that I think can be attached / hung from a bolt just below the frame brackets. There seems to be plenty of space to move the front mounting points on the saddle frame and adequate space to add any brackets under the rear to position springs in line with the frame mounts. I'll post a pic when it's fitted. Thanks again.

Offline Dougiethenoo

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Re: Mk III Sport restoration
« Reply #8 on: 08 Jan 2016 at 11:07 »

If it is a help for you, I will make a photo. The bikes are still in restauration!

Michael

Photos are always helpful and I appreciate seeing any pictures of other MkIIIs to see what others have done to restore and improve them!
Thanks.

Offline Dougiethenoo

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Re: Mk III Sport restoration
« Reply #9 on: 17 Jan 2016 at 15:17 »
Eddie,
Do you know of any comparable size generic silencers available to mimic the MkIII sport?
The later Mk silencers have an angle on the input that means they need to be rotated when used "upturned" and this puts the mounting lug on the outside, or if ground off, leaves an unsightly unchromed patch!

Douglas MkIIIS by Dougiethenoo, on Flickr

Thanks.

quote author=eddie link=topic=6026.msg22152#msg22152 date=1449846366]
Douggie,
              The exhaust pipes just have two 5/16"BSF nuts brazed on the side to take the short dome head heatshield bolts.
  If you are replacing the exhaust system, be aware that the Mk3 Sports silencers were quite a bit longer than the Mk4/5 silencers, so if you are going to have new pipes made and fit Mk5 silencers, it might be a good idea to make the pipes extra long so that they can be trimmed, when you have decided the best position for the silencers.
Regards,
               Eddie.
[/quote]

Offline eddie

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Re: Mk III Sport restoration
« Reply #10 on: 17 Jan 2016 at 15:53 »
Hi,
     The Mark 3 Sports silencers were peculiar to that machine. The intake pipe was the same size (1 3/8" bore) as the Mark 5 barrel silencer but the barrel was longer and the tailpipe longer and bigger in diameter (about 1 5/8"). Mark 3 sports silencers also had a mounting stud brazed on the inside of the tailpipe to pick up the lug on the subframe.  The later Mark barrel type silencers are just a straight silencer and can be fitted any way up (there are no angled inlets, etc) and will fit straight onto the Sports exhaust pipes but look odd due to them being short (the upswept sports pipes being much shorter than the downswept Mk5 pipes). If your silencer has an angled inlet, then someone has bent it! (either intentionally or when they have dropped the bike).
  The exhaust in your photo is not Mk3 sports - it is much too long - it looks more like an inverted Mk5 system. On the Mk3 Sports, the silencer clip should be almost vertically above the lower mounting for the rear subframe.
  If your silencers have a mounting boss on the side of the main barrel (as would appear in the photo), they are not Mk5 but Dragonfly silencers.

  Regards,
               Eddie.

Offline Dougiethenoo

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Re: Mk III Sport restoration
« Reply #11 on: 17 Jan 2016 at 20:02 »
Thanks.
I can see the length difference from other photos of MkIII sport models.
I could shorten a later exhaust pipe - but the problem with this pair is that when rotated up, the bend is too deep and the front of the pipe will interfere with the mudguard.

I have found a source of 1 3/8" OD polished stainless tube and am looking for someone with the right bending equipment.

If anyone can measure from the cylinder head forward to the very front of the exhaust on an original MkIIIS exhaust, that would help me get the bend done right.

Many thanks.

Offline Dougiethenoo

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Re: Mk III Sport restoration
« Reply #12 on: 21 Jan 2016 at 19:29 »
     The Mark 3 Sports silencers were peculiar to that machine. The intake pipe was the same size (1 3/8" bore) as the Mark 5 barrel silencer but the barrel was longer and the tailpipe longer and bigger in diameter (about 1 5/8"). Mark 3 sports silencers also had a mounting stud brazed on the inside of the tailpipe to pick up the lug on the subframe. 

HELP! Could anyone with an original MkIII Sport exhaust confirm the silencer barrel diameter, length and tail pipe length?
I am in the process of having some fabricated in stainless and would like to get as close as possible to the original.

Thanks in advance!

Offline giz.neal

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Re: Mk III Sport restoration
« Reply #13 on: 25 Jan 2016 at 14:47 »
The silencers on my Mk IIIS were made by Armours in the UK to order a number of years ago. They are of good quality but neede some additional silencing material. Some very quick rough measurements:

Diameter of input and tail pipe 38mm (1 1/2")

Input end 44mm (1 3/4")

'Barrel' (main body) length 340mm (13 1/4"), Diameter 76.5mm (3")

Tail pipe 120mm (4 3/4"), mounting lug is on the tail pipe 38mm (1 1/2") from the end of the 'barrel' portion.

Overall length approx 20" (510mm)

These measurements are a little vague as the formed portion of the silencer marking the transition between input barrel and tail pipe is difficult to measure using my  Heath Robinson methods, this marks the slight disparity.

Offline Dougiethenoo

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Re: Mk III Sport restoration
« Reply #14 on: 26 Jan 2016 at 02:00 »
Thanks!

Offline eddie

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Re: Mk III Sport restoration
« Reply #15 on: 26 Jan 2016 at 07:36 »
Hi,
    Attached, is a photo taken at the works of a Mark 3 Sports - it shows to good effect the silencer with a larger bore tailpipe ( it may be good enough to scale the dimensions!). Note - this is one of the early machines with the toolboxes with a single knob.

  Regards,
                Eddie.

Offline Dougiethenoo

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Re: Mk III Sport restoration
« Reply #16 on: 26 Jan 2016 at 16:42 »
Thanks, looks like the tailpipe is about 2" OD, but could be 1 3/4" I guess.
I am working on a design of welded stainless silencer as a replica and will post pictures if it ends up being cost-effective to make.
Main concern is that it will be quite heavy since the scrap stainless tube I have is around 2mm wall thickness.

But the new polished stainless "up" pipes will look much better, even with the old MkV or Dragonfly silencers on.

Offline tck

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Re: Mk III Sport restoration
« Reply #17 on: 28 Jan 2016 at 07:41 »
the only difficult part of a silencer to make are the end domes every other tube part can be found on the net having said that to find a welder good enough to weld the items so that zero  weld defects show when cleaned and polished is very hard.
NB back in the early sixties most of the silencers on mk5 dougies I knew had burgess silencers some with 'BURGESS" imprinted down their length.

Offline eddie

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Re: Mk III Sport restoration
« Reply #18 on: 28 Jan 2016 at 09:33 »
Attached is a photo of the replica silencers I made in stainless (with the help of an expert welder) for the ISDT Douglas. As per the originals, they just have a perforated centre tube surrounded with fibreglass packing. They give a nice soft note on tickover, but do speak quite loudly on full bore!

  Regards,
               Eddie.

Offline douglas1947

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Re: Mk III Sport restoration
« Reply #19 on: 29 Jan 2016 at 06:04 »
The photo of the MK3 Sports shows a toolbox with 1 lid srew in the middle.
Is there also an other type of boxes for the Sports with 2 lid srews (left and right) ?

Michael

Offline eddie

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Re: Mk III Sport restoration
« Reply #20 on: 29 Jan 2016 at 06:35 »
Michael,
             Attached is a photo of the more usual toolbox with 2 screws. This was a cast alloy box with a separate lid, whereas the prototype box was thought to have been a pressed steel box with a hinged lid - hence the single screw!

  Regards,
                Eddie.

Offline douglas1947

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Re: Mk III Sport restoration
« Reply #21 on: 29 Jan 2016 at 11:42 »
Thanks for the information, Eddie.

The 1 lid box looks a bit like R. Enfield rigid toolbox, are it the same ?

Michael

Offline Dougiethenoo

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Re: Mk III Sport restoration
« Reply #22 on: 05 Feb 2016 at 01:06 »
More on the Mk III sport exhausts: I've ordered a pair of exhaust "up" pipes to be made in polished 304 Stainless, 1-3/8" OD, 15 GA.
The radius is slightly smaller than the standard since the dies were only available in 2.5" or 3".



Offline eddie

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Re: Mk III Sport restoration
« Reply #23 on: 05 Feb 2016 at 06:50 »
Dougie,
            I don't know where this drawing originated, but it is not a Douglas works drawing - that would have shown a part number which would have identified the pipe as being left or right hand fitting. The right and left hand pipes are different in that the mounting bosses (nuts) for the exhaust guards are on opposite sides, and the straight tail that goes into the cylinder head is longer on the left hand pipe by 1.3 inches (because of the offset on the cylinders).
  Regards,
                Eddie.

Offline eddie

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Re: Mk III Sport restoration
« Reply #24 on: 05 Feb 2016 at 08:54 »
Dougie,
            Having had a second look at the drawing, I've noticed a couple of errors! The O.D. of the tube should be 1.375" (not 1.325"), and the measurement over the outside of the bend will be 7.38" (not 7.33") if the centreline describes a 6.00" diameter. Another observation - taking into account the springback when manipulating stainless steel, a pipe bent around a standard 2D former will probably spring out to near on the correct radius!
  Regards,
               Eddie.

Offline Dougiethenoo

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Re: Mk III Sport restoration
« Reply #25 on: 05 Feb 2016 at 13:34 »
Dougie,
            Having had a second look at the drawing, I've noticed a couple of errors! The O.D. of the tube should be 1.375" (not 1.325"), and the measurement over the outside of the bend will be 7.38" (not 7.33") if the centreline describes a 6.00" diameter. Another observation - taking into account the springback when manipulating stainless steel, a pipe bent around a standard 2D former will probably spring out to near on the correct radius!
  Regards,
               Eddie.

Thanks Eddie, I appreciate the QC! I had not noticed that dimensional error.
It's a new solidworks drawing to fabricate replicas - and I'm updating it before sending to the mandrel bender.
When I have offered the new pipes up to fit, I'll trim both ends to length to suit the mounting points and cylinder offset, and ensure mudguard clearance on full lock! And then place the captive nuts for the heat shields.
All this requires making and re-attaching new silencer hanger brackets which have been cut off the subframe, which will be slotted to allow some adjustment if the bend isn't perfectly parallel or springs out a little.
I have not decided yet whether to splash out on fabrication of smaller diameter longer silencers or use the Burgess or Dragonfly replicas I have.
I'd be interested to know the technique you used to get the domed ends of the silencer body on that beautiful replica you posted above?

On the cylinder head end, the steel pipes had a welded collar - but I plan to use finned clamps from a Triumph T140, which are also 1 3/8" and reasonably unobtrusive.
Cheers
Ian.

Offline eddie

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Re: Mk III Sport restoration
« Reply #26 on: 05 Feb 2016 at 15:20 »
Hi,
    For the domed ends, I started by turning up a steel domed plug about 1/8" undersize, leaving a 1" dia flat on the end. I then bored a 1" hole x " deep in the end. I then made a 1" plug with a 1" spigot to fit. The blanks for the domes were then cut with a 1" hole in them. The plug located them centrally on the former. I then took the whole lot to a company that specialised in metal spinning and got them to do the actual spinning. That just left the holes to be opened out to suit the intake and tail pipes.
 Originally, on the Mark series machines, the pipes just pushed into the cylinderheads - any finned clamps were just aftermarket extras that only clamped to the pipe - they had no affect on the attachment of the pipe (I use exhaust assembly paste - Holts Firegum in the UK - to seal the pipes in the head). On the 80/90Plus machines, the pipes are retained by screwed collars - Douglas found the finned variety destroyed the airflow over the heads, resulting in overheating. Later Plus machines just had a plain screwed collar!
  Regards,
               Eddie.

Offline Dougiethenoo

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Re: Mk III Sport restoration
« Reply #27 on: 05 Feb 2016 at 22:34 »
Thanks Eddie, I hadn't considered they may disrupt the cooling. I was toying with the idea of springs on a collar to hold them in but Firegum seems to have worked fine for the last 67 years!

Offline Dougiethenoo

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Re: Mk III Sport restoration
« Reply #28 on: 14 Feb 2016 at 14:40 »
The silencers on my Mk IIIS were made by Armours in the UK to order a number of years ago. They are of good quality but neede some additional silencing material. Some very quick rough measurements:

Diameter of input and tail pipe 38mm (1 1/2")

Input end 44mm (1 3/4")

'Barrel' (main body) length 340mm (13 1/4"), Diameter 76.5mm (3")

Tail pipe 120mm (4 3/4"), mounting lug is on the tail pipe 38mm (1 1/2") from the end of the 'barrel' portion.

Overall length approx 20" (510mm)

These measurements are a little vague as the formed portion of the silencer marking the transition between input barrel and tail pipe is difficult to measure using my  Heath Robinson methods, this marks the slight disparity.

Thanks - I note that the Universal fit Burgess style silencers offered on Feked http://www.feked.com/universal-burgess-type-british-classic-silencer-21-id-35-51mm.html appear to match these dimensions quite well and are certainly closer to the Mk3S silencer than the units they offer for this model, which appear to be the same as the Dragonfly silencers.

Offline Dougiethenoo

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Re: Mk III Sport restoration
« Reply #29 on: 14 Apr 2016 at 14:49 »
Making some progress!!
 :D

Offline Dougiethenoo

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Re: Mk III Sport restoration
« Reply #30 on: 26 Apr 2016 at 03:50 »
Anybody got a spare rear mudguard in restorable condition?

Generic aluminium ones will fit with some modification but are a little too large a radius.


Offline Killipso

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Re: Mk III Sport restoration
« Reply #31 on: 26 Aug 2016 at 08:29 »
I have been looking at posts recently as I built up to doing some work on my MKIII. I came on this interesting post with that fantastic replica silencer of Eddie's. I require replacements also and have been considering options for some time i.e.. Armours etc.. Originals have all been shot to pieces and no better than the ones I have already. Anyway, I thought I'd add a photo or two of my originals. They have the narrower end pipe as illustrations of the the later MKIIIs with the dual closing knob tool boxes (Douglas Motorcycle Range (LDMCC [re]print, 50th Anniversary, page 14). The one in the photo, like its partner, is rusted through and well worn.



(For reference: In case its not clear because of perspectival distortion, the silencer opening on the left in the photo is lined up with the paving slab edge and the start of tape measure).

If anyone wants measurements I could provide them though at present I can't find my verniers or outside callipers.
« Last Edit: 26 Aug 2016 at 08:41 by Killipso »

Offline Killipso

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Re: Mk III Sport restoration
« Reply #32 on: 26 Aug 2016 at 08:47 »
And for an illustration of the internal construction of the Burgess I'm attaching a PDF that includes a cutaway view (this is how my silencers are reconstructed).


Offline eddie

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Re: Mk III Sport restoration
« Reply #33 on: 26 Aug 2016 at 09:04 »
The original Burgess silencers fitted to the Mk 3 Sports and 'Plus' machines had the internal tubular baffle the full length of the barrel. Only in later years did the design alter to that shown in the above view. Evidently, in an attempt to reduce some of the 'sportier' exhaust notes, the law was amended with the requirement of a physical baffle to reduce the noise level (not that this was necessary with absorbtion silencers like the Burgess), so Burgess altered their design to incorporate a chamber with the curved baffle at the inlet end - so that their units complied with the then normal check that baffles were fitted (by poking a broom handle, or the like, up the silencer!!). At that time, we hadn't got into the realm of noise meters - or type approval!
  Regards,
               Eddie.
« Last Edit: 26 Aug 2016 at 09:12 by eddie »

Offline Killipso

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Re: Mk III Sport restoration
« Reply #34 on: 26 Aug 2016 at 11:14 »
Hi Eddie, thanks for the update, just the kind of detail that helps keep everything glued together. When did that law change happen - or rather when did the later design come to market? I'm slowly trying to piece together my knowledge as I put my MK back together. Cheers,  Raif (killipso)

Offline eddie

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Re: Mk III Sport restoration
« Reply #35 on: 26 Aug 2016 at 11:29 »
Late 50's, I think. Probably after Douglas production terminated, but Burgess would probably have been listing replacement silencers for quite a few more years, so silencers of the later pattern would have been fitted to, otherwise, original machines. I bought a scruffy Mk3 Sports in 1961 - it had been stored outside and the silencers had rotted through, but they were of the original design with the full length baffle and the large O.D. tail pipe.
  Regards,
               Eddie.

Offline Killipso

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Re: Mk III Sport restoration
« Reply #36 on: 26 Aug 2016 at 13:18 »
Hi Eddie, thanks for the clarification. Are your replicas street legal or too noisy?

Offline eddie

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Re: Mk III Sport restoration
« Reply #37 on: 26 Aug 2016 at 16:39 »
Raif,
        I have 2 bikes with that design of silencer fitted. My Dragonfly has the shorter version and sounds much the same as the original Burgess silencers. The longer version on the 6 days bike gives a sharper bark that is probably a bit over the limit (I would have expected the longer silencer to give a softer note). I have convinced myself that the sharper note is down to the longer pipes on the 6 days bike - another odd feature is that, even after a long, hard ride, the silencers are still cool enough to touch with the hand - I guess it must be something to do with the resonance within the pipe and the distance from the cylinderhead.

  Eddie.

Offline Killipso

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Re: Mk III Sport restoration
« Reply #38 on: 26 Aug 2016 at 17:11 »
Hi Eddie, ....food for thought there. Have been considering how to build new ones for some time. I had a conversation with Dave Lawrence a few years ago regarding the Burgess embossing on the originals and got him to send me a silicon mould of the logo on some good conditioned originals he or a friend of his had. On my silencers the logos are polished out almost from a previous refuelling. Anyway, I'd hoped to get some forms made and then to roll or fly press some sheet or tube for the main barrels - expensive of course but I'd hoped I might get some help from one of the departments at work - politics got in the way.... I continue to look for opportunity.

Raif

Offline Killipso

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Re: Mk III Sport restoration
« Reply #39 on: 28 Aug 2016 at 09:56 »
For reference and prompted by the earlier question about seat springs... Attached below low and high res images of original 1950s/60s stock springs for my MKIII.

This has eight coils but I have at least one spring that has more 10 coils while the same overall length:


Showing the form of the ends:


Showing the length at 143mm:


Showing outside diameter at 48mm:


Still haven't got the verniers to get the gauge. With outside calipers I measure 5mm OD. The ten coil spring I have is 6mm OD.

(Attached are the full resolution images)
« Last Edit: 28 Aug 2016 at 11:15 by Killipso »

Offline Dougiethenoo

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Re: Mk III Sport restoration
« Reply #40 on: 28 Aug 2016 at 15:58 »
With regard to replacement silencers, after seeing the dimensions posted here by various helpful folks, I found a set of Dorset silencers that are very close to the dimensions of the original silencers but lack the mounting boss. Since I had made new stainless steel up-pipes, with a slightly smaller radius bend, I used a clamp and fabricated a hanger bolt to attach them to the original mounting points. The dimensions are not exact - but they are close enough to make it all fit together in approximately the right place compared to the various reference photos. The silencers were purchased from www.feked.com.

Douglas Mk III Sport with exhausts fitted by Dougiethenoo, on Flickr