Eddie Dow type damping on 1958 Huntmaster front forks.

[johnduckworth55]

Just made a pair of the non return devices as per drawing found on a BSA site, exactly the same drawing as I found on the Ariel site. The top mounting on the stanchion nuts is sorted and I can add oil through the chrome 1/2" plugs on the outside of the nacelle. Question is how long do i make the rods ? It is my opinion that the lower face of the non return device should be just above (say 6mm) the uppermost bleed hole on the stanchion. This would ensure that when approx 7 fluid ounces of oil is added that the unit would be constantly submerged. Any thoughts ?

[Steven.Carter]

Just made a pair of the non return devices as per drawing found on a BSA site, exactly the same drawing as I found on the Ariel site. The top mounting on the stanchion nuts is sorted and I can add oil through the chrome 1/2" plugs on the outside of the nacelle. Question is how long do i make the rods ? It is my opinion that the lower face of the non return device should be just above (say 6mm) the uppermost bleed hole on the stanchion. This would ensure that when approx 7 fluid ounces of oil is added that the unit would be constantly submerged. Any thoughts ?

I've a pair fitted in mine, a few years ago now so can't actually remember how I fitted them. But filling oil through those top holes is very difficult, smand slow I'll look back and see of I took any photos

Steve

[Steven.Carter]

Found a picture John, I can see how I found it difficult to fill,

[pete.collings]

When I fitted a set in my early type teleforks, I added enough oil so that the damper units were just covered with oil with the forks on full extension. It was much easier to adjust the oil levels with my setup, as I used an alloy top yoke but later type sliders, having fitted an 8" Norton front brake wheel with a modified spindle and spindle sleeve.
I can well understand that the later nacelle setup would make it more difficult ro add/remove oil, in previous times I have used a syringe and thin plastic piping cut to the length needed.

[johnduckworth55]

No problem adding oil; the problem I have is ascertaining the distance from the top yolk face to the bottom face of the damping device and thereby establishing the length to make the rods. I am aware that if they are too long there is a risk of the bullet shape rod in the bottom of the slider hitting the damping device. Also I am slightly concerned that I could obstruct the two bleed holes with the device, hence I feel that the device should be at least 6mm above the upper bleed hole. Any thoughts ?

[Roger Gwynn]

The BSA drawing should be correct given that the stanchions, at least post 1954 and all modern replacements, are the same length on Ariel and BSA. The only difference might be the top nut. I have a not on a drawing that I did when I made mine to say "3/8 dia rod length so that bottom of damper valve is 16-11/16" from top face of top yoke or so that valve is in the oil at full extension". I must say that in spite of trying various thicknesses of oil I didn't find much improvement. I also fitted variable rate springs but took them out as they were too stiff for an alloy rigid machine being intended for an overweight BSA A10 s/arm.

[johnduckworth55]

Thanks for the replies. Just looks like I will have to experiment with oil levels etc. The overall length of the units I have made is 19 1/4" measured from the underside of the fork top stanchion bolt to the end of the damper unit which places the extremity of the damper unit approx 6mm above the upper bleed hole in the stanchion. The amount of oil which is required to cover the damper units at full fork extension is 220 - 225ml (7.7 - 7.9 fluid ounces). I intend to use ATF in preference to oil. I'm beginning to wonder if it is all going to be worth the effort. Incidentally I have Ariel documentation regarding fork oil capacity and one Service manual states 6.5 fluid ounces and another manual states 7.0 fluid ounces. I will be using between 7.7 - 7.9 fluid ounces as above. As can be seen from the images I have modified the top nuts and made adaptors, thus making it relatively easy to add oil, and retain the original plugs and top screws in the nacelle.

[simon.holyfield]

Are you far away from road testing John?

[johnduckworth55]

Simon,
just put everything back together today, Eddie Dow damper units, dual rate springs from SRM and 225ml of ATF. I don't think I will be riding it until Easter time as I have a few more jobs to do. I use my very rough 1957 350NH when there is salt on the roads. If I can remember I will let you know any improvement after road testing, I'm not holding my breath! Incidentally I have four Ariels with exactly the same forks and they all feel different on the front end.
Regards. John.

[jj.palmer]

John, is this the drawing that you are referring to, sorry that it is on its side, this one does not give the diameter of the centre orifice hole or the the required clearance between the outside diameter (0.9 in) and the bore of the stanchion. I would have thought those features to be important as to control the oil flow and hence the damping effect.

I have previously measured the position of the 2 bleed holes in the stanchion from the top yoke by using a long steel rod with a pointer attached and then feeling for the holes as the pointer enters.

John P.