Eddie Dow type damping on 1958 Huntmaster front forks.

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Simon.Gardiner
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Re: Eddie Dow type damping on 1958 Huntmaster front forks.

Post by Simon.Gardiner »

The original drawing comes from here (I think we should make some reference to the original source!)
https://www.a7a10.net/forum/index.php?topic=2895.0

From the discussion in that thread:
"Hopefully the attached sketch will enable those of you who would like to make your own "Taylor Dow" type damper valves for their BSA's
The original TD valves used 3/8in. diamater rods threaded 3/8 BSF and a 9/32in ball bearing (try finding those now!!)
Pattern ones sometimes have 10mm rods and 8mm ball bearings..."
"...What's the diameter of the small hole in the bottom of the valve body? 0.125" as well?" (That size was confirmed.)
"...One other modification...was to enlarge the central hole from 1/8 to 7/32 inch to reduce the harshness on compression."

A Forum search on 'Eddie' will come up with a wealth of info on fork mods......

SG
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'55 Huntmaster, '56 VH, ' 51 VH, '62 Arrow, '80 R100RT, '00 Sprint ST (now with a new Arrow project, and just now those 4-stroke Ariel parts can't even make one running bike...)
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Re: Eddie Dow type damping on 1958 Huntmaster front forks.

Post by jj.palmer »

Simon, thanks for the info., it is the same drawing, can now add the missing data.

John P.
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Re: Eddie Dow type damping on 1958 Huntmaster front forks.

Post by johnduckworth55 »

John,
I seem to recall that somewhere along with this drawing on the BSA site that a question had been asked regarding the diameter of the aforementioned hole and the answer by the gentleman who drew the damper up was 1/8". However a friend of mine fitted a pair to his rigid VH500 and was advised to open the holes up to 9/64" as the 1/8" hole was more suitable for racing, therefore the units I have manufactured have a 9/64" hole. I will see if there is any improvement when I road test the machine.
Regards, John.
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Re: Eddie Dow type damping on 1958 Huntmaster front forks.

Post by jj.palmer »

Thanks John, it seems that people have to make one or two changes to get the damping correct ie change hole sizes, change oil.

I am wondering if there is anyway that the oil flow through the valve can be adjusted without taking everything apart, front wheel off etc.

Does anyone know of any literature out there were someone may have tried this.

John P.
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Re: Eddie Dow type damping on 1958 Huntmaster front forks.

Post by simon.holyfield »

jj.palmer wrote: Tue Jan 18, 2022 11:22 am Thanks John, it seems that people have to make one or two changes to get the damping correct ie change hole sizes, change oil.

I am wondering if there is anyway that the oil flow through the valve can be adjusted without taking everything apart, front wheel off etc.

Does anyone know of any literature out there were someone may have tried this.

John P.
You could make the part with the hole removable, like a carburettor jet. Obviously you would have to pull the rod to change the jet...
cheers

Simes

'51 Square Four,
'58 Huntmaster,
'42 W/NG,
'30 Model A
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Re: Eddie Dow type damping on 1958 Huntmaster front forks.

Post by jj.palmer »

Been scratching the head to think of how the damping can easily and quickly be adjusted without having to remove the front wheel etc., and then with fingers crossed, hoping that you have chosen the correct hole size.

This is only an idea at this stage, comments, criticisms are welcome, see attached drawings.

The damping resistance works by controlling the outflow of oil from the unit rather than the inflow as per the ED method. The outflow is varied by the repositioning the ball bearing relative to the outflow holes, thereby, changing the aperature size through which the oil flows. Repositioning of the ball bearing is done by shortening or lengthening the ball rod, see drawing sheet 2.

The damping unit can be lifted up through the top yoke to enable adjustment to the damping, no need for removal of the front wheel etc.,
once lifted out a special tool is attached. The lock nut/threaded bar assembly is then removed which gives access to withdrawing the ball rod which in turn can be lengthened or shortened to change the damping resistance, see drawing sheet 1.

My estimate is that you could change the damping settings in both forks within say 1 hour, therefore in a relative short time you could have tested various settings to find the optimum that suits or you could have a variety of ball rods to suit various riding conditions.

Sorry the pics are on their side.

John P.
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Re: Eddie Dow type damping on 1958 Huntmaster front forks.

Post by Bob.Murphy »

I love the concept of a "removable hole" :lol: :lol: :lol: .

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Re: Eddie Dow type damping on 1958 Huntmaster front forks.

Post by simon.holyfield »

You could consider changing the four outlet holes for multiple smaller holes drilled radially along the length of the insert, to reduce the damping effect vs. number of turns of the central rod. This would increase the resolution of the adjustment. As it is, you will turn the adjuster maybe three turns from 'full open' to 'full close'.

The other idea I've been toying with is some kind of adjustable spring loading to dynamically restrict the damping according to the rate of compression...
cheers

Simes

'51 Square Four,
'58 Huntmaster,
'42 W/NG,
'30 Model A
https://ariel-square-four.blogspot.com
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Re: Eddie Dow type damping on 1958 Huntmaster front forks.

Post by Roger Gwynn »

Or use a different viscosity oil, just a thought...thinner oil flows more freely etc. The 1956-58 forks have a drain hole but one can be added to earlier forks - carefully.
Roger Gwynn, Membership Secretary, curator of the Machine Register and the works drawings. Director of Draganfly Motorcycles, Craven Equipment and Supreme Motorcycles mostly retired.
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Re: Eddie Dow type damping on 1958 Huntmaster front forks.

Post by simon.holyfield »

simon.holyfield wrote: Wed Jan 19, 2022 7:23 pm The other idea I've been toying with is some kind of adjustable spring loading to dynamically restrict the damping according to the rate of compression...
I've been looking at this article. It shouldn't be too difficult to design a spring loaded valve into the Eddie Dow type rod, to provide less damping on sudden, sharp bumps - closing again to return to normal, higher, low speed /anti-dive damping...

https://racetech.com/page/title/Emulato ... hey%20Work
cheers

Simes

'51 Square Four,
'58 Huntmaster,
'42 W/NG,
'30 Model A
https://ariel-square-four.blogspot.com
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