Author Topic: DT5 help please  (Read 13205 times)

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Offline Dave

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DT5 help please
« on: 16 Jun 2011 at 09:55 »
Chris in Hong Kong (chris hkg) sent in these photos and request for assistance.

Quote from: Chris
Hi guys,

I have been reading posts for a couple of years now and it's time my project got started.

From "ident your Douglas" section I have a 1931(?) DT 5, frame TF 1061D, eng OE 873X and Gearbox YG 450, see attach photos.
The bike has been idle for at least 50yrs, but fully (?) restored my now deceased uncle. It's now mine and I'd like to see her running with me in control!(or at least on board).

I've read that the DT's did not have a clutch, but then re-read, that because the model was so popular a road version was produced (presumably with clutch and brakes) to enable riding to/from the track the rider was competing at.

My bike has a clutch that isn't working and needs a thrust bearing, springs and screws, can anyone help?
The post by davebarkshire " clutch setup 1926 EW" has photos that look to be identical. Confirm/deny?

I see from other posts that LDMCC has a spare parts section, can anyone please tell me if they would be able to help.

cheers,
chris (in) hkg












Offline chris hkg

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Re: DT5 help please
« Reply #1 on: 16 Jun 2011 at 10:26 »
thanks Dave for posting my request, it now appears again a few minutes later as I managed to downsize the photos.
standing by for some advice coming my way!
chris hkg

Offline eddie

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Re: DT5 help please
« Reply #2 on: 16 Jun 2011 at 11:07 »
Chris,
          From the pictures and the numbers you have quoted, your bike seems to have DT / SW cycle parts but is fitted with the earlier OB type engine (hence the screw collars on the exhausts and inlet pipes). The later DT/SW machines had flanged fittings and engine numbers starting EL****. The clutch is also the earlier type with the rounded edge to the flywheel (SW models had a squarer edge to the flywheel). The clutch on most of the SV models operated on just one side of the plate, whereas the OHV models had the normal double sided plate, and can be identified by having 3 driving pins in the black painted area of the flywheel. You would have to dismantle the clutch to determine which sort of thrust bearing is fitted - some were plain bronze, others had balls and hardened tracks (and there were 2 sizes of these).
           Hope this is of some help,
                      Regards,
                             Eddie.

Offline chris hkg

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Re: DT5 help please
« Reply #3 on: 16 Jun 2011 at 11:29 »
Hi Eddie,
thanks for the reply, I must admit to being a little confused and I too thought the engine maybe from the 1924-5 OB 600 OHV, engines OE*** (3*S), but scrolling down the identify your Douglas chart you come to the 1931 DT model with engines OE**** (4*s), mine is  OE873X, does the X qualify as the 4th *?

Offline eddie

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Re: DT5 help please
« Reply #4 on: 16 Jun 2011 at 16:48 »
Chris,
          Engine number OE873X would be fairly late in the OB series. Douglas numbered each model of their 1920/30 era frames and engines starting with 100. In the Douglas Club machine register, there are several OB engines with 3 digits and ending with an 'X' (all listed as 1924 models). All the DT5/6 and SW5/6 engines were prefixed EL. There are also some other odd engine numbers with a 75 prefix where owners have fitted 750cc motors that were originally intended for aircraft use.
          Regards,
                     Eddie.

Offline Dave

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Re: DT5 help please
« Reply #5 on: 16 Jun 2011 at 19:21 »
Chris,

I removed the other post as Eddie has already replied to this one and the content was much the same.

Dave

Offline Doug

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Re: DT5 help please
« Reply #6 on: 17 Jun 2011 at 00:51 »
Quote
...but scrolling down the identify your Douglas chart you come to the 1931 DT model with engines OE****...

Chris, you are referring to the short-stroke DT of 1931. This is an error in the chart based on what I thought was an original short-stroke DT engine, but which I since figured out was a set of OB crankcases impressed into duty into a genuine short-stroke frame. I am now inclined to believe the short-stroke DT engines just continued to used EL prefixes from the long stroke motors. This will be corrected in the next revision of the identity tables.

There are actually two and three peg OHV flywheels, the change over seems to have occurred in 1931. And there were two variations of the two peg I believe. Douglas continually evolved the flywheel clutch from 1923 to 1935 (far as I know the design remained unchanged after that until the end of prewar production in 1938.) Regardless of the number of pegs the purpose was the same, and that was to drive the pressure plate used on the OHV models. As Eddie says, they had the 'conventional' arrangement of lining on both sides of the clutch disk.

-Doug

Offline Doug

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Re: DT5 help please
« Reply #7 on: 17 Jun 2011 at 01:22 »
Quote from: Chris
I've read that the DT's did not have a clutch, but then re-read, that because the model was so popular a road version was produced (presumably with clutch and brakes) to enable riding to/from the track the rider was competing at.

Correct. DT had no need for clutch or brakes. Provision for the rear brake is there because the DT was using frame lugs from the contemporary road going model OC, and the head stock of the 1923-25 RA model. Since the DT did not use the OC forks (they are very similar), they had the opportunity to omit the lug on the fork blade for the brake anchorage/lever. Douglas added brakes and clutch in 1930 and sold it as the SW model. This was to replace the OC road model, which had been discontinued. In theory you could ride the machine to the track and go racing on a road circuit, but I can not see anyone using on on the cinders as they would be at such a disadvantage against the specialty dirt track machines superseding Douglas at the time, like Rudge. Anyway, it is fairly easy to add brakes and clutch to a DT, and many were converted (and are still being converted) to give them a useful extension on life as a road machine. All you need do is find donor components from another Douglas model; there is a lot of parts interchangeability. An anchorage needs to be added to the front fork blade, but this was a add-on by Douglas and so is easy to replicate. DTs only had a foot rest on one side. SW had footrest lugs on both sides, as well I think late DT frames. You will see quite a few road going DTs where one footest is a brazed lug and the other is a butt weld (added later.) Then the only thing left to solve is the gearbox problem. DTs used ultra-close ratios, not so much for racing as to suit the length of track. Once you started there was not time to change gears. This does not give a wide spread of ratios for the road, so some sort of compromise ends up being made unless you can find a rare set of road ratios. Only the ratios changed, the gearbox shell is dimensionally identical. Many modify and install a Norton gearbox.

-Doug

Offline chris hkg

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Re: DT5 help please
« Reply #8 on: 17 Jun 2011 at 10:31 »
thanks again gentlemen!
food for thought, it sounds like of got a home made job, another couple of pictures posted for you to view,



« Last Edit: 19 Jun 2011 at 10:25 by Dave »

Offline graeme

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Re: DT5 help please
« Reply #9 on: 17 Jun 2011 at 12:49 »
Certainly the timing side is not standard OB - the airbox and carburettor set up look to be from an early DT model.
Nice machine in the background too!  :)

Offline Doug

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Re: DT5 help please
« Reply #10 on: 18 Jun 2011 at 02:19 »
Chris,

The rear sprocket pre-dates the DT era as well. DTs had circular lightening holes. The sprocket shown was used on Douglas machines like the OB, OW, RA. This opens the possibility the hub (and wheel?) came from the same donor as the sprocket.

-Doug

Offline chris hkg

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Re: DT5 help please
« Reply #11 on: 18 Jun 2011 at 05:27 »
starting to sound like I have an OB that wanted to go to the track!

Offline chris hkg

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Re: DT5 help please
« Reply #12 on: 22 Jun 2011 at 06:39 »
I've now attached a photo of the clutch insides..
my mate has made a spacer the same size (?) as the thrust race we're after, 2 1/4''OD,- 1 3/4'' ID- 0.107''Thou
Sprocket bearing = balls
does this make sense?
stamped letters appear to be D, X, H
thanks again,
Chris

« Last Edit: 22 Jun 2011 at 21:39 by Dave »

Offline eddie

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Re: DT5 help please
« Reply #13 on: 22 Jun 2011 at 07:43 »
Chris,
          In the photo you have just posted, there is a loose steel ring - this is one of the hardened tracks for the thrust race. There should be a similar track (possibly with a centralising spigot) in the operating lever/ cam. Between these there should be a brass/bronze cage to carry a set of " balls - the thickness of the cage should be about .156".
       The thrust bearing assembly should fit between the operating cam and the collar surrounding the centre boss of the flywheel. Operating the clutch then pushes that collar out against the pressure of the clutch springs - thus freeing the clutch. This may not be obvious at the moment as you probably have already removed the springs during removal of the flywheel, and therefore have nothing for the cam to press against!

                     Regards,
                                     Eddie.

Offline chris hkg

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Re: DT5 help please
« Reply #14 on: 22 Jun 2011 at 08:14 »
Hi Eddie,
the loose ring was made as a spacer by the guy who took it apart (not me). I gather the 'race' self destructed or was not even there as I've NOT seen any evidence of it's existence when taken out and so that's what I'm after!!
Can I buy the thrust race and springs now that we know the size and if you could identify which model it's meant to be part of ? , I gather the OB as that's the engine.
thanks and cheers!
Chris

Offline chris hkg

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Re: DT5 help please
« Reply #15 on: 26 Jun 2011 at 02:43 »
good morning gentlemen,
another couple of questions for you..?
Since the OE engine is established to be (probably 1925 600 OHV model), should I rename my DT 5 a DT 6 ?
What are the chances of the early days of DT production  (frame 1061 ) that the factory threw in a OE engine?

Offline Doug

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Re: DT5 help please
« Reply #16 on: 26 Jun 2011 at 13:19 »
Chris,

You could call your DT 'Gertrude'; what you call it does not matter so much as getting it going again!   :)

While there were DT6 models cataloged, I think they were dropped early on just like the 350cc version was (except to special order) due to lack of events to use them at. Someone that knows cinder track racing history may be able to provide more authoritative details on that aspect.

The chances of the factory fitting a OB engine due to lack of suitable EL prefix engines would be I think nil. I have seen engine and frame combinations under production number fifteen. Frame number 1061 (961 off the line) would not be considered a particularly low number. It is more likely something happened to the original engine and it was replaced by a readily available OB engine. For all intents and purposes the engine units are interchangeable (as are many of the components.) When the factory released the EL crankcases, they took the opportunity to make the crankcases heavier, presumably to better stand the rigors of competition. The crankshaft and connecting rods were also upgraded. Externally they are very similar and indeed, the factory modified the existing OB/OC patterns to use on the DT. Residual features of the OB can still be seen on the DT engine!

-Doug


Offline chris hkg

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Re: DT5 help please
« Reply #17 on: 27 Jun 2011 at 11:02 »
I kinda like Gertrude!
I think the name will stick and yes getting 'her' going is the priority.


'

Offline chris hkg

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Re: DT5 help please
« Reply #18 on: 03 Oct 2011 at 03:08 »
still having problems with clutch, as what we have just doesn't look right.
can anyone out there give me direction as to where a thrust race bearing can be got?
is there an exploded diagram showing dimensions if we have to resort to 'home made'.
I have indeed joined up and got some springs from pre-war spares but unfortunately no bearing,
cheers
Chris in hkg

Offline Ian

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Re: DT5 help please
« Reply #19 on: 03 Oct 2011 at 21:15 »
Chris, after I rebuilt the clutch on my OC we ended up with not enough clearance for the thrust race - and on the advice of a few forum folk used a sintered bronze ring instead. This has worked beautifully !!


Offline chris hkg

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Re: DT5 help please
« Reply #21 on: 04 Oct 2011 at 02:11 »
thanks Doug!
love your work!!

Offline chris hkg

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Re: DT5 help please
« Reply #22 on: 17 Aug 2012 at 04:26 »
Hello again everyone.
The project has been slow, but have had a motivation kick in the backside after visiting Sammy Miller's museum in the UK and seeing his fantastic bikes including a DT Douglas.
Eddie, you asked me the diameter of the flywheel  = 250mm and the taper on the crankshaft, that's 25-22mm, and the threaded end is 5/8". Can you identify the clutch from this on 'Gertrude'? (OB?)
The clutch on the bike at the moment seems to be missing parts and we tried fitting a steel spacer. The bit in there seemed to resemble one that had been destroyed by over work. This too failed BUT NOT UNTIL AFTER the engine fired up and ran beautifully for a couple of minutes. The 1st time in many (50+?) years.
If anyone out there knows what we are missing and where we can get the bits and pieces it would be greatly appreciated.
Is anyone taking such pieces to Victor Harbour in September??
cheers
Chris

Offline eddie

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Re: DT5 help please
« Reply #23 on: 17 Aug 2012 at 07:22 »
Chris,
        As the crankshaft taper only measures 25mm I am pretty sure that the whole of your engine is either OB or OC (but with a DT airbox grafted on). From the photos you posted last year, it looks as if the clutch linings are rivetted to the flywheel backplate, so presumably your clutch has a one sided driveplate - in which case, lifting the clutch just moves the driveplate away from the backplate. This is the same setup as used on the sidevalve models of the same era. The loose ring shown in your previous photos is one half of the thrust bearing - this should fit over the boss of the flywheel and bear against the face of the clutch sprocket - and there should be a matching half that fits into the clutch release cam. Between these 2 halves there should be a bronze ring with trapped ball bearings - this completes the thrust bearing assembly. When the whole clutch is fully assembled, there should be some free play on the clutch release lever - if there isn't, the thrust bearing will be under permanent load, and will fail prematurely. Likewise, when the cable is fitted, it should be adjusted so that there is about 1/8" of free movement.
     If you are attempting to re-manufacture the tracks for the thrust bearing, they should be made out of good quality case hardening steel. Ideally they need to end up being glass hard on the surface but with a tougher core to withstand the loads that will be applied.

     Regards,
                 Eddie.

Offline chris hkg

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Re: DT5 help please
« Reply #24 on: 17 Aug 2012 at 09:35 »
Once again thank you Eddie, standby for updates in the not too distant future, cheers Chris

Offline roy

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Re: DT5 help please
« Reply #25 on: 17 Aug 2012 at 10:42 »
Chris, further to Eddies post, if the clutch is the same as the side-valve models, I have posted photos of my 1927 EW clutch.









« Last Edit: 26 Aug 2012 at 18:23 by Dave »

Offline chris hkg

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Re: DT5 help please
« Reply #26 on: 17 Aug 2012 at 11:23 »
Thanks Roy! It's 21:25 here in Melbourne and the bike's at my mate's place, will compare soon. Cheers

Offline chris hkg

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Re: DT5 help please
« Reply #27 on: 10 Nov 2015 at 00:19 »
5+ years later,
got the old girl (Gertrude) fired up on the front cylinder only (plug removed on rear).
Beautiful sights n sounds !
the attempt on the clutch disintegrated in a shower of sparks shortly after.
I admit defeat.
We are not getting any younger.
Can anyone out there recommend a Douglas motorcycle restorer, preferably in Australia?