Recent Posts

Pages: 1 2 3 [4] 5 6 ... 10
31
British Bikes / Re: Albion gearbox BF436 - where used?
« Last post by 33d6 on May 18, 2026, 09:13:23 AM »
Also used on the ultra-ultra cheap 98cc Villiers Midget powered machines brought out in 1931 to keep factories ticking over in the depths of the Great Depression. Excelsior were the first in April 1931 with their 14 guineas (!4 pound & 14 shillings) utility model 0, that's 0 for zero, not the letter O. When your normal range is all numbered models starting at Model 1 for the smallest, a 150cc bike, then how do you number the even smaller new 98cc model you're introducing? It becomes the Model 0.
Within weeks Coventry Eagle, Dot and Sun had also introduced their 98cc Midget powered bikes, all with the same 2-speed no kick starter box. Both Wolf and Gloria (name used by Triumph) followed on shortly afterwards. Reputedly it also sold in Continental Europe but I don't have any information on them.
The various road tests all emphasised how easy they were to start by just pushing off with your feet but very quickly the slightly more expensive kick start version of the same two speed box was offered as an extra.

So, that box could have come out of a number of makes until at least the middle 1930's. Information is sparse on all of them.

Deciphering the Albion gearbox numbering system is another thing altogether and isn't very helpful as you still have to deal with the slightly different versions of the same box which the numbering system doesn't seem to recognise.
32
British Bikes / Re: Albion gearbox BF436 - where used?
« Last post by cardan on May 11, 2026, 08:05:32 AM »
There were many variants of Albion boxes! This is the 2-speed + clutch variant. In the 1931 catalogue for "Albion Midget Gear Boxes" this model (identical?) was referred to as the BJ. I know nothing, but maybe BF was an earlier model, say 1927?? In 1931 the EJ gave 3 speeds + clutch + ks.

Anyway, no reason it couldn't go into a bike from the 1920s, although Australian made stuff (for example, I'm thinking Waratah) tended to offer 2-speed no-clutch for a base model, or fancy 3-speed + clutch + ks. Although by 1927 maybe even the basic 2-speeder needed a clutch.

Also, chain final drive was taking over from belt around 1927.

Leon
33
British Bikes / Re: Albion gearbox BF436 - where used?
« Last post by Albion EJ on May 11, 2026, 05:16:37 AM »
Could be a “5”.

Does BF mean something?
34
British Bikes / Re: Albion gearbox BF436 - where used?
« Last post by R on May 10, 2026, 11:19:40 PM »
i see BF456  ?

Not that it makes much difference in identifying them by number from the gazillions of types ....
35
British Bikes / Albion gearbox BF436 - where used?
« Last post by Albion EJ on May 10, 2026, 06:04:08 PM »
Does anybody know where this gearbox (2 gears?) was used?

As it is not equipped with a kickstarter it might be a stationary engine.

Thanks!
36
British Bikes / Re: Tiger cub valve timing.
« Last post by cardan on April 22, 2026, 11:51:57 PM »
Yes Rex you're absolutely right, but reducing the inlet charge by 3% is more-or-less like reducing the CR by 3% - there's less gas in there to squish. Of course when everything is spinning at 6000 rpm all the static calculations are out the window anyway!

Leon
37
British Bikes / Re: Tiger cub valve timing.
« Last post by Rex on April 22, 2026, 09:59:01 AM »
I think I'd rather look into skimming the piston crown before altering the valve timing.
Personally I can't see how altering the valve timing would or can alter the CR, given that it's a ratio of swept volume to compressed volume of the cylinder.
The CR would be the same even if there were no valves in place.
Altering the amount of time that the inlet valve is open may alter the amount of mixture entering the engine, but that's not the CR.
38
British Bikes / Re: Tiger cub valve timing.
« Last post by Vreagh on April 22, 2026, 09:19:54 AM »
Thanks Leon, although that doesn't sound much, I think it's worth a go. The effect would be greater with 7:1 piston so might be just enough.
  Cheers, Keith
39
British Bikes / Re: Tiger cub valve timing.
« Last post by cardan on April 22, 2026, 06:51:44 AM »
I've calculated the change in compression ratio, guessing that a Cub con rod is about 4 1/2" long.

Delaying the close of the inlet valve from 55 degrees after BDC to 60 degrees after BDC changes the (static) compression ratio by about 3% - if it was 9:1, it would drop to around 8.7:1. Not sure how that feels in real life.

Leon
40
British Bikes / Re: Tiger cub valve timing.
« Last post by cardan on April 22, 2026, 03:00:01 AM »
Hi Keith,

You could certainly give it a go.

The inlet valve closes when it does because someone at the factory has determined that this is the point, when running "normally", that gets the most mixture into the cylinder. For a sporty little engine like the Cub the inlet closes quite late, because running at higher revs there's a lot of intertia of the gas flowing from the inlet port into the engine. So the cylinder keeps filling even though the piston is moving UP the cylinder on the compression stroke.

Cub timing figures attached, from www.triumphrat.net/attachments/cub-useful-data-page-with-timin-specs-1966-jpg.755483/

At starting, the engine is spinning very slowly. Let's imagine that we turn it really slowly, say by hand. Letting the inlet valve close later will mean that the piston is slightly higher up the bore before the inlet valve closes - the extra volume of gas (equal to the distance up the stroke times the area of the piston) has been pushed backwards out the inlet valve, so the amount of gas to be compressed is less. We could calculate it, but I really doubt it could make too much difference to the compression on the first rotation of the engine. Once spinning, the gas flow is a very dynamic thing and depends on all sorts of stuff I'm not qualified to talk about!

What it will almost certainly do is cause blow-back through the carb when the engine is running.

But give it a go and let us know how you get on. Good luck!

Leon
Pages: 1 2 3 [4] 5 6 ... 10