Author Topic: Douglas frame numbers  (Read 1926 times)

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Offline Oldbiker

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Douglas frame numbers
« on: 30 Dec 2018 at 18:50 »
Hello I have just aquired a Douglas motorcycle. It is registered as a1936 Aero 600cc. The frame number of FZ 228 does not appear to be correct for an Aero, this number is stamped on the right hand side of the frame just beneath the saddle. There is another number stamped on the underside of the crosstube at the bottom of the frame, this number is EXP 12894.    15430?.
The bike is fitted with a rear stand which looks correct, not a centre stand?
Is it possible that the bike started life as a different model or year?

Offline eddie

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Re: Douglas frame numbers
« Reply #1 on: 30 Dec 2018 at 20:27 »
According to the LDMCC machine register, frames with an FZ prefix were fitted to 1935 Blue Chief models (500cc). There are only 9 of them known to exist. The correct engine for that model had a 5/H prefix. Douglas machines at that time were not selling well, so it is possible that your 1935 machine did not get registered until some time in 1936.

  Hope this helps,
                            Regards,
                                          Eddie.

Offline Doug

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Re: Douglas frame numbers
« Reply #2 on: 30 Dec 2018 at 20:54 »
According to the catalog illustration, the Blue Chief would have used a center stand. The stops on the mid-thirties Douglas center stands and frame lugs were quite weak (all models!), so it would not be a surprise of someone fitted a rear stand. The Blue Chief also features a knock out rear axle, so the frame would have a significantly different rear axle lug compared to other models. It is not clear if this was an option or all Blue Chiefs were fitted so.

Barring that, the other noticeable difference between a Blue Chief and the subsequent Aero frame was Blue Chief used a tee-lug at the lower extremity of the front down tube. The Aero used a lug-less connection. The engine rails were bent in a U-shape at the front (no tee) and the down tube gas welded to it (no lug).

Likewise the Aero engine is a close development of the Blue Chief. Gone are the aluminum barrels and cylinder heads to be replaced with cast iron. The gear oil pump  at the base of the timing chest and oil feed to the end of the crankshaft is gone, replaced by a multi-stage reciprocating pump as already being used on other models. The crankshaft is no longer drilled, rather a simpler spray bar the drizzles oil on the path of the crankshaft supplanted it.

So the Aero was similar to the Blue Chief, but would have been more economical to manufacture.

-Doug

Offline Oldbiker

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Re: Douglas frame numbers
« Reply #3 on: 02 Jan 2019 at 16:25 »
Many thanks for the information, I still have a lot to learn about the bike, I have now got it ready for blast cleaning and repainting. It must have originally been fitted with a centre stand as I can now see marks in the frame crosstube where has been rattling against it. I hope that this is the correct way to answer to your replies

                                                                         Many thanks
                                                                                                  John

Offline Doug

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Re: Douglas frame numbers
« Reply #4 on: 03 Jan 2019 at 03:04 »
John,

Here is a picture of the 1935 Blue Chief. Note what looks like a hubcap at the rear axle covering the bearing-in-frame for the knock-out axle. Also the bulk at the base of the front down tube that is a frame lug. 1935 was also the last year for an instrument panel in the petrol tank.



Compare the above to a 1936 Aero. Conventional rear lug axle. Smooth juncture at the base of the front down tube of the welded joint. No instrument panel.




The Blue Chief is shown with the 3-speed gearbox, but the 4-speed was probably an option since it was introduced as early as 1932 on the big side-valves. Whether a 3- or 4-speed was fitted made no difference as far as the frame was concerned. The two frame tubes that the engine sat on continued back past the the saddle post for the transmission to clamp to.

-Doug

Offline Oldbiker

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Re: Douglas frame numbers
« Reply #5 on: 03 Jan 2019 at 11:26 »
Doug, thanks for the images my bike looks more like the Aero than the Blue Chief.

                                                                                            Many thanks
                                                                                                                    John

Offline Doug

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Re: Douglas frame numbers
« Reply #6 on: 03 Jan 2019 at 20:10 »
John,

Strange it is stamped as a Blue Chief and has the features of the Aero. Maybe the Aero features were a running improvement introduced partway through 1935? Or... my two Aero 600 frames are stamped under the saddle on the LEFT. Perhaps check to see if there is a second number on that side?

-Doug

Offline Oldbiker

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Re: Douglas frame numbers
« Reply #7 on: 04 Jan 2019 at 08:37 »
Doug,

           I have already checked the opposite side, there no numbers, I am assuming that the left and right sides are when sat on the bike and not when facing the bike from the front. The only other number is stamped on the bottom frame crosstube, that number is EXP 12894. 154330.
           
                                                                                                              John

Offline eddie

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Re: Douglas frame numbers
« Reply #8 on: 04 Jan 2019 at 08:59 »
John/Doug,
                    Applying a bit of lateral thinking - could this bike (or just the frame) possibly have been used for pre - production testing of the proposed new frame for the Aero?? - in which case, the frame would have carried a Blue Chief number (to keep the registration authorities happy, and camouflage the existence of a new model) but have the construction of an Aero frame for (perhaps) long distance road testing. The 'EXP' number being the factory's way of identifying which of their experimental frames was the most reliable or most economical to produce.

  Sorry if I have muddied the waters!!

   Eddie.

Offline Oldbiker

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Re: Douglas frame numbers
« Reply #9 on: 04 Jan 2019 at 11:49 »
Eddie,
           Well the frame has now gone to be blast cleaned, when I get it back in a week's time I will be able to see if the paint is hiding some more hidden secrets! On the subject of the EXP number I was wondering if it had been a competition frame of some kind?

John

Offline eddie

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Re: Douglas frame numbers
« Reply #10 on: 04 Jan 2019 at 14:26 »
John,
         I doubt that it was a 'competition' frame - from 1933 until the war, Douglas were struggling financially and had ceased supporting any competition events. Following the war, the 'EXP' frame numbers surfaced again on the prototype T35's.

  Regards,
                Eddie.

Offline Doug

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Re: Douglas frame numbers
« Reply #11 on: 04 Jan 2019 at 14:33 »
John,

Yes, number on the left when astride the bike. An example form one of my frames:



You can use this to check the fonts against what is stamped on your frame.

Douglas did use "EXP xxxx" as a part numbering system for experimental and pre-production components as evidenced by references on some of the factory drawings to other parts or the use of stampings. For example 'Use stamping EXP xxxx until suplies run out'. I cannot think of having seen an example on an actual part. Indeed, I have only seen a part number on a casting when it was worked into the pattern, if even then. I've not seen a part number stamped. Douglas used a chronological numbering assignment for part numbers. So numbers assigned to the Blue Chief are seen from mid-16k to 17k range. Much of the Aero part numbers would overlap as they are likely the same components as the Blue Chief (nuts, bolts, knee grip plates, etc), excluding the parts they actually did change.  So they run from the upper 16k range to about 17k as well, and the 1937 models run into the 18k range. I am not sure exactly how the experimental numbering worked. During the DT era the experimental numbers seem to have lagged behind the production numbering. Not sure if they have their own numbering pool, or (most likely) if it was just simply because the experimental number had been assigned months or even half a year prior.

But the number you found on the bottom of the frame is most likely a component number. It is about in the right numeric range and too many digits for a frame serial number. Nor have I heard of them using EXP as a prefix for competition machines. They just used the same or the next assignment of their standard frame numbering format (including an "F" for frame.) True one-off specials are more likely than not to have no number.

If another number does not turn up, then my guess would be it is a Blue Chief frame that the factory built up or modified as a pre-production Aero frame. I don't know which side of the frame the Blue Chief was stamped on. If most were stamped on the left, then that would be another anomaly. On the F28, 350EW, and A31 they are stamped on the left, so I assumed that was the preferred side.

-Doug

Offline Oldbiker

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Re: Douglas frame numbers
« Reply #12 on: 04 Jan 2019 at 15:07 »
Doug,
           That is the same font as mine but definitely stamped on the opposite side. The number stamped under the frame is also in that font using larger digits.

           Perhaps the man who stamped the frame just got it on the wrong side!

                                                                                                                    John.
« Last Edit: 04 Jan 2019 at 17:30 by Oldbiker »

Offline Oldbiker

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Re: Douglas frame numbers
« Reply #13 on: 08 Jan 2019 at 15:03 »
Doug/Eddie
                     I now have the registration document for the bike it shows that it was registered on 03/11/1936 and that the frame number is recorded as FZ228DEXP12894. There is no model type recorded.  It has a 5/L engine with larger cylinders to make it 600cc and is fitted with Webb heavy girder forks. So I think it must have had an interesting journey so far, we will see what the future brings.

                                                                                                     Many thanks for your help
                                                                                                                                                    John.

Offline Red

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Re: Douglas frame numbers
« Reply #14 on: 05 Jul 2019 at 18:36 »
Just to add to this. I have just recently acquired what is registered as a 1936 Aero 500 which I noticed had the wrong frame, but as the price was right we bought for my son. It hadn't been on the road for 4 or 5 years, but once we got home and cleaned out the fuel tank and carburettor and put some fresh oil in it started up and rode OK. Engine sounds good and clutch and gearbox all work OK. It is now stripped for restoration and I intend to use the same frame. Attached is a photo of the frame number - FN 136  and what looks like another N at the end although the font doesn't look right. This appears to be a Wessex frame from the number unless I've got it wrong. Any one else got any suggestions. Thanks

PS - Wiill try to add the photo to another post

« Last Edit: 05 Jul 2019 at 18:46 by Red »

Offline Red

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Re: Douglas frame numbers
« Reply #15 on: 05 Jul 2019 at 18:43 »
Photo of frame number

Offline Daren W Australia

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Re: Douglas frame numbers
« Reply #16 on: 05 Jul 2019 at 20:40 »
Hi the N is a superimposed DK for Douglas Kingswood regards Daren
too many dougli not enough time!

Offline Doug

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Re: Douglas frame numbers
« Reply #17 on: 05 Jul 2019 at 20:51 »
Red,

As Daren says, the last digit is the Douglas Kingswood trademark. FN prefix code would be a 1934 model Z, but yes, called the Wessex in 1935 (or 5Z). Not sure what the difference between the Z and the 5Z would be (if any). Normally if there was no physical change they would just continue on into the next year with the same frame prefix code.

-Doug

Offline Red

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Re: Douglas frame numbers
« Reply #18 on: 06 Jul 2019 at 09:51 »
Hi - Doug / Darren

Thanks for the information.

Roy