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Dave

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Racing Douglas - help needed

Started by Les Rowe, 30 May 2006 at 13:06

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Les Rowe

I wonder if anyone can provide some "go fast" tips, or at least some "not going quite so slow" tips for my 2 3/4hp model, which I'm trying to prepare for historic Period 1 racing in South Australia.

I have had it out on the track for practice and was shocked at how slow it was after it had seemed fairly quick on the public road.

Ideally, I would like to buy a second engine I can develop rather than rely solely on the one that is in it, and if some extra speed can be found, a front brake would be really handy!
Can anyone help out?

I have attached a photo of me on the bike at Mac Park in Mount Gambier, South Australia. The photo was kindly supplied by John Bonney Photography. Visit his website here where there is a large number of racing photos including of local Period 1 star Ian Collett on his 1912 TT Triumph.

Hoping to get Douglas back on the podium,

Les Rowe.



Larger view

alwyn

#1
Hi,
That's a great action photo Les - I've placed a copy over in Members Gallery too.

Alwyn
Global Mod.

Quotable Quote - "640 k should be enough for anybody"! - Bill Gates - 1981.

Doug

This has got to be a wind up.  Tell me you are joking? 

2-3/4hp engines have a weak center crankshaft web that have been known to break if you push them hard while touring.  And have you seen the connecting rods?  More like thin strips of flatbar.  This is not an engine you want to spin too fast, it is not robust enough to take the inertial loadings, yet lacks the vibration that warns you have gone too far, till it goes 'bang!' 

I think you will be much happier vintage racing something else, I fear your plans to race a 2-3/4hp will only end in tears.   :cry:

-Doug

Les Rowe

#3
Quote from: Doug on 31 May 2006 at 03:18
This has got to be a wind up.  Tell me you are joking? ...... Doug

Thanks for your comments Doug, I take them on board and I promise not to rev it out past "red line" - but it's no wind up.

You should not equate racing a bike with the unbridled abuse of that bike ("to finish first, first you have to finish").

I have a few other bikes in the stable (unfortunately no other Douglas) and must admit that I prefer to ride them as I feel they should be ridden, which is perhaps a bit more on the brisk side than the sedate side. Unfortunately some have indeed gone 'bang' on occasion, but then it's a matter of fixing/improving it so it doesn't go 'bang' again. At least not in the same place.

All part of the fun (and didn't someone say,"competition improves the breed"!?).

Les.

Daren W Australia

#4
found this on the web it may inspire Regards Daren

too many dougli not enough time!

Dave

#5
Note the dropped handlebars and the riding position to reduce wind resistance. In the cycling world, a lot of attention is paid to minimising wind resistance.

QuoteOn a flat road, aerodynamic drag is by far the greatest barrier to a cyclist's speed, accounting for 70 to 90 percent of the resistance felt when pedaling.

http://www.exploratorium.edu/cycling/aerodynamics1.html

There are lots of handy calculators on the Web for calculating the power required to overcome wind resistance at different speeds. The one on the above link is designed for bicycles but will give you a rough idea of the power required at different speeds to overcome wind resistance.

Some sort of related articles -  http://www.msgroup.org/forums/mtt/topic.asp?TOPIC_ID=72 and http://www.msgroup.org/TIP180.html

Dave

alwyn

Quote from: Dave on 01 Jun 2006 at 11:06
Note the dropped handlebars and the riding position to reduce wind resistance.  Dave

There you have it Les! - get them handlebars down, your saddle back a notch and your bum up!!

Only kidding  ;-)

Alwyn

Quotable Quote - "640 k should be enough for anybody"! - Bill Gates - 1981.

Les Rowe


There you have it Les! - get them handlebars down, your saddle back a notch and your bum up!!


The light-weight helmet must be the secret!

Chris

Can I inject a serious note into this discussion? The question asked by Les Rowe at the start of this thread is one that was asked by many owners when the machines were new especially as Douglas based their publicity on their sporting and racing prowess. Douglas certainly knew how to make their machines go faster and many other pattern suppliers tried to jump on the band wagon. You will note in virtually all Douglas handbooks and often in their advertisements that Douglas stressed the need to buy genuine spare parts only. This was because there was a thriving market in pattern parts just as today when you can buy non genuine spares for virtually any make of car.

There was one well known firm in the Bristol area who even produced a catalogue of parts for the Douglas. They included high compression pistons, special exhaust systems and many other goodies, indeed there was a multitude of alternative exhaust designs by various manufacturers. How effective any of these measures were is open to debate now but there are some 2. 3/4hp machines that are known to be very quick. The main ingredient in this performance is a different cam. There are several different cams fitted to 2.3/4 hp models at different dates of manufacture but the TT model had one different from those fitted in production. I am still waiting to get my hands on one of these to see how it compares with the normal 5, 5A or 5B cams.

The strength of the engine has been raised as a concern in this discussion. For normal production, to reduce flexing of the cam spindle and its effect on the diamond frame a longer spindle was provided for the cam with an outrigger bearing in the timing chest cover. Another improvement available is the H section con-rods fitted to some models. These are quite rare and are obviously much stronger than the usual flat strip rods. I have a pair in one engine. I do not know when they were introduced or what models used them originally.

The crankshaft still remains a weakness but more so now with 80 to 95 years of use when they are all probably fatigued and at least slightly worn. In recognition of this, gentle and careful use is the order of the day as there is a finite supply of parts. High speeds and racing is inevitably going to result in major costly failures.   Chris.

Daren W Australia

Hi Have a close look at the photos it has a rare factory Over Head Valve conversionon on a 2 3/4 as pointed out by Eric Bourn who has seen one ! Regards Daren
too many dougli not enough time!