Author Topic: New OC Type to Group  (Read 1864 times)

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Offline OCTypeCanada

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New OC Type to Group
« on: 08 Nov 2012 at 02:22 »
Hello everyone,  I am new to the group and have recently acquired an OC type Douglas with frame number E320D.  The engine to go into the bike is an OHV valve unit with number EL 102.2 stamped into the casing.  The bike frame is in good condition with all important tin ware intact and restorable, as are the forks.  Missing from the bike are the transmission and both front and rear hubs.  Can the group members help me with info as to the correct hubs (does anyone have spares to sell?) and correct transmission  (any tranny's for sale).  I lack any literature for the bike and would appreciate knowing if the heavy weight bikes shared transmission types to the lighter 350 cc bikes?
  I unfortunately do not have Douglas spares but do have some spares for mid '20's AJS 350 and 500 cc bikes.

Thanks, Gord (Canada) 

Thanks for the feedback so far!  I have loaded a few pictures, two of the frame and one of the engine.  If clear enough, the pictures show the shifter coming up through the fuel tank.  Did any Douglas bikes other than the OC have this feature?
« Last Edit: 09 Nov 2012 at 03:00 by OCTypeCanada »

Offline David Lawrence

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Re: New OC Type to Group
« Reply #1 on: 08 Nov 2012 at 23:42 »
Hi Gord,
Welcome to the Douglas fraternity....
Regarding your OC frame, I think you may have misread the number, they are often very indistinct and full of paint/rust! All the frames of this era have two letter designations before the numerical digits. OC frames are LF***  only three numbers, Douglas made very few of this model! The D you have after the number is almost certainly the Douglas Kingswood trade mark which was a K superimposed on the D, I am sure you will receive a posting from "Doug" before too long, you will see the mark as he uses it has his avatar!
Regarding the engine, this designation shows the motor to have originated from a 1928 era DT or SW machine it should read EL1202 I am not sure how the full point has come about.
Good luck with finding wheels, if you cannot find a Douglas gearbox many OHV models have been fitted with period Norton gearboxes, at the same time using the Norton clutch thus removing the need for a flywheel Douglas unit. I am sure you will recieve advice on this if the conversion is suitable for an OC frame.
The effort of rebuilding the bike will be well worth it! they are very sporty!
Dave

Offline Ian

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Re: New OC Type to Group
« Reply #2 on: 09 Nov 2012 at 01:17 »
Regarding transmission the gearbox is specific to the 600 I think - mine has a TG prefix

Offline Doug

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Re: New OC Type to Group
« Reply #3 on: 09 Nov 2012 at 13:13 »
Gord,

The gearbox shell is identical to that used on the contemporary TT model as well as the later DT/SW models. What makes the unique are the serial number's prefix, and the internal gear ratios they denoted. For the OC, three options were available; UG (presumably normal, and also the TT model), TG (touring, wide ratio), and SG (close ratio). There is also VG, very wide ratio as used on the TT; and YG, which was the ultra close ratio gearbox used on the DT. Later SW models used the UG or TG.

So shells abound, the problem is the gears. The most abundant gearbox one comes across is the YG. You may start to slather thinking about sporty pretensions of fitting an ultra close ratio 'racing' gearbox. Forget it! The interbox ratios are 1:1.5, 1:1.25, and 1:1 (direct.) There is not enough spread to make a useful road going three speed gearbox. Not unless you like wringing the engine at 55mph maximum, or alternately having a first gear that starts at 25mph. These boxes were intended to be stuffed in one gear that best suited the length of the track, and left there.

Gearsets for the road ratio boxes are much, much more scarce. This is the problem I ran into when I rebuilt the transmission for my SW, and I ended up making new gears. I did manufacture some spare sets, but they sold out long ago. There are 2nd gear pairs still available. This is a link to the old advert, if you manage to find a gearbox. 

http://www.douglasmotorcycles.net/index.php?topic=117.msg276#msg276

I need to do a little research on the hub situation. They might be common to other models of the era.

Doug

Offline OCTypeCanada

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Re: New OC Type to Group
« Reply #4 on: 11 Jan 2018 at 16:30 »
Doug, regarding the engine in the picture, do you know where I can access some literature that would help in rebuilding the engine? (hopefully the picture still shows in this chain of correspondence)

Gord

Offline Doug

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Re: New OC Type to Group
« Reply #5 on: 11 Jan 2018 at 18:21 »
Gord,

I have yet to see a handbook or a parts list for the OC. Much of the engine rebuilding is standard small engine practice, except for the roller bearing crankshaft. That requires some specialized tooling and some experience to do right. The engine prefix you call out (EL) is for the  subsequent DT model, which is similar to the OC engine. There is a parts list for the 1929 iteration, but not seen a handbook for the DT either. Purchasers of a DT were involved in competition and were expected to be able to handle their own engines without a book! Interchanging the entire unit or major components is not a problem as the differences are just in details. OC used threaded exhaust ports, DT use flanged ports; OC had an oil pump in the timing chest, early DT was hand oiled, later (small airbox) had a pump; and so on. Some new bits an pieces have been made for the DT and are advertised here on the DMF (full disclosure: by me!) The previous model was the OB, the the LDMCC does a reprint of the handbook for that which talks about specs and some reconditioning aspects of the engine that would apply to the OC. I have done a few crankshafts, but they are time consuming and expensive. Big end cages are the next item in short supply that need to be put back in production. In this regard the correct crankshaft for the OC used an earlier style conrod and crowded rollers on a lighter crankshaft. Finishing up two DT engines this spring (I hope!), one for a client and one for my SW5.

-Doug

 

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