Improving the front forks

[andrew.chapman]

Thanks David. As it happens, I already have some PTFE tape. I use it for sealing tapered threads. I have never really thought of trying to use it on a parallel thread. I will give it a go.

AndyC

[david.anderson]

Doc1.docx

(89.54 KiB) Downloaded 540 times

Doc1.docx

(89.54 KiB) Downloaded 540 times

For those interested in improving the Ariel fork damping please see the following link where details of the Eddie Dow type dampers are provided.
(http://www.audioworld.net/BSA/forum/ind ... ttach=7512)
While Dow dampers are a big improvement and will provide compression damping where there was previously none, the forks will not perform like a modern cartridge fork (ie there will be excessive dive under braking and hydraulic lock may be experienced on large bumps which will result in teeth jarring).
The fork damping improvements shown in the September, Cheval De Fer will not actually improve damping. The repositioning of the hole in the fork leg will ensure that the hydraulic stop will work rather than the forks topping out with metal to metal contact. The new damper plug will only provide minimal damping over about the last inch of travel before the forks bottom. Again the new plug does more to provide a hydraulic stop than improve damping.
Cartridge type forks are superior in that the fork can differentiate between low and high speed damping which results in less fork dive under braking but more comfort over bumps. While it does not appear possible to adapt a cartridge to an Ariel due to the fork leg size, cartridge emulators are a device that will make a damper rod fork behave like a cartridge fork. They only provide compression damping so you have to rely on the existing rebound damping
As such I purchased a pair of cartridge emulators (which are designed to sit on a damper tube and are held in place by an internal fork spring) for fitment in my square 4. I have considered fitting the bottom legs of a B44 as that would make the fitting of the emulators easy, but that would destroy the originality of my bike. It would also be possible to machine up a damper tube for pre 1956 forks for fitting to the thread that holds the tapered plug, but it would also be necessary to dispense with the nut that holds the bottom fork bush in position to facilitate a damper tube of adequate size. The bottom fork leg bush could then be held in position with circlips.
I decided however to mount the emulators on a rod suspended from the top fork nuts as per the Dow type damper. This involved machining a 1” bush to which I silver soldered the body of the emulator. The bush may be machined to take a brass piston ring or O ring to ensure proper sealing but I am trying tight tolerances abt .001 clearance in the fork leg. The top emulator valve is then dropped into position after which I soft soldered the top part into position. The bottom emulator valve was then screwed into position and the damper adjusting screw fitted through the top valve. At this stage the assembly was fitted to the top rod and suspended from the top nut. To adjust the damping it is necessary to remove the headlight nacelle assembly, undo the top fork nut, remove the assembly from the damper rod and then turn the adjusting screw. My initial setting was inadequate. I am currently running 4 turns on the adjusting screw with 20w engine oil (so as to not affect the rebound damping) which is a big improvement but I need more time now to ride the bike and evaluate the setting. The emulators I used are from mikesxs at $54 a pair. http://www.mikesxs.net/products-19.html#products
It maybe better to use a slightly smaller emulator (made by racetech)which would give a little more side clearance and allow the sides of the bush to extend further down the emulator so that soft solder could be used to hold the emulator in place

[Vincent.vanGinneke]

O.K. I could follow your description until about 2/3 down your text, >>to which I silver soldered the body of the emulator. The bush may....<<
then I got lost (expecting hollow laughter from the back row now..................)
Did you by any change take pictures ?
I looked at the XS parts site but cannot figure how you get these cartridge emulators into the Ariel forks.
Please let us have a pictorial story on "Ariel fork damping for dumbo's"

Vincent

[Keith.owen]

Hi fellow Arielists,
I spoke to Clay at Acme to see if he could make me some fork bottom end valves (as per the drawing in Cheval).

He needs to buy a tool to be able to do it. He recons that if there is enough interest he could make them from between £12 to £14 /pair including tooling charges. I volunteered to ask on our forum to see how much inetrest there might be.

Thoughts anyone?

[david.anderson]

Vincent
Unfortunately I didn't take any photos and as it has been raining here for the last couple of weekends I haven't ridden the bike again or done any adjusting. Basically the emulator is an adjustable damper that will give good high speed and low speed compression damping. I decided to mount the emulator in a similar fashion to a dow type damper inside the staunchion and in the oil, suspended by an alloy rod from the top fork nuts. In order to work all the oil in the bottom leg must be forced through the emulator. As such I made a bush that is a tight fit inside the staunchion. Simply put the emulator is silver soldered to the bottom of the bush and the bush is hollow for most of its height. The bush is tapered toward the top then it attaches to the 1/2'rod. There are a series of holes from the taper into the centre of the bush to allow the oil to flow. The adjusting spring for the emulator extends up inside the bush. (in reality the emulator is completely dismantled before the body is silver soldered to the bush. The top part of the bush above the taper is detachable and fixed with soft solder in order that the top valve of the emulator can be fed down into position and assembled after the emulator is silver soldered to the bottom of bush. After the top part of the bush is soft soldered into the bottom part the bush, the adjusting spring and fixing screw is fed down the threaded 1/2"hole to which the damper rod attaches. The screw feeds through the emulator top valve and the spring tension is set to give the desired damping. The assembly is then threaded onto the damper rod. My damper adjuster is currently set with 4 turns of preload.)
As the fork leg rises under compression the oil in the bottom leg is forced up the centre of the staunchion through the emulator into the hollow bush and out of the bush through the holes in the taper just below the alloy rod that suspends the assembly from the top nut. The emulator has an adjustable valve that restricts the passage of oil and provides the compression damping. On rebound another valve in the emulator opens and allows the unrestricted flow of oil back into the fork leg. As such there is no rebound damping provided by the emulator but that is handled by the existing holes in the Ariel fork staunchion.
Sorry I didnt explain it that well. the diagram that is attached to my previous post may help you to make more sense of it. regards. David

[Vincent.vanGinneke]

Hello david, Thanks again for doing your best to explain it! I just looked at the document in your earlier posting and I think I get the clue.
You silver soldered the Yamaha bit into the bit with the "8 evenly positioned 4mm holes" and you soft soldered the "soft solder to lower bush" bit into that again, because the top valve of the emulator has to go in before .......ehhhhh, yes?
You made the damper rod in alloy, is that chosen because of weight? it does not buckle under pressure?
I can imagine that the oil pressure inside can get pretty high on inward move.

Now all I have to do is get that old Weiler LD220 from the far rear of my shed, dismantle and clean/repair it after being abused for 30 years by kids at my school,.... and get to grips with turning up some of these bushes.

Vincent

[david.anderson]

Vincent
Yes you have it. the reason I used 8 4mm holes is that the area of those 8 holes is slightly bigger than the area of the emulator valve. As such there would not be any damping except that provided by the emulator.
The rods in my Eddie Dow dampers on my VH are 3/8” aluminium and have never looked like being a problem. I would have used 3/8 aluminium rods to suspend the emulator, but the emulator spring and adjusting screw are the last parts assembled and are fed down through the hole that is drilled and tapped for aluminium rod. A 3/8 hole less thread was not big enough to pass the spring through. It was necessary to go to 12mm or ½”. I don’t believe the ½”rod will ever buckle. The loads on the Dow type damper would be higher as the damping is constant. The emulator valve will however open further with a large jolt therefore reducing the damping force applied, which puts less load on the rod.
the reason that I used silver solder to attach the emulator is that the attachment area is minimal. I soft soldered the top part of the bush as the contact area is much greater. In both instances only compression forces are applied to the joints and both surfaces sit against a shoulder which means the solder is not under any stress
Regards
David

[simon.holyfield]

Hi David,

It seems like us Arielisti keep our bikes for a long time.

At some point I will need to look at the forks rebuild for my FH - and I am always interested in improving my bikes. My SQ4 is completely standard (except in the electrical department) so I would be interested in your views on damping modifications 9 years on!

Either Dow or Yamaha options look like a suitable project for a recently-retired enthusiast with a lathe and a TIG welder!

[david.anderson]

Simes
Yes the forks on all my bikes are upgraded, although only 2 of them have the cartridge emulators fitted, and one of them is my favourite VH. My other Ariels have Dow type damping. The damping stops the wallowing that can otherwise occur and high speed stability is improved.
For fork oil I use auto transmission fluid which is a lighter oil than originally used. ATF contains anti frothing additives which makes them ideal for use in forks (and I was given a 20 litre drum years ago so it is hard to beat pricewise.)
On a bumpy road the Dow damper does give a lot harsher ride than the cartridge emulator does.
The emulator has separate ports that control low speed and high speed damping. Low speed damping is typically the gentle push of hard braking whereas the high speed damping is a sharp jolt of a pothole. The low speed damping is through a fixed orifice whereas the high speed damping is through a spring loaded valve. With a very harsh jolt the high speed valve opens further, reducing the damping and softening the ride. So the emulator provides damping that adapts to the conditions.
If your roads are good there is nothing wrong with the Dow dampers.
Setting up the emulator was a little time consuming. After figuring out the mounting system and fitting them to the bike, I then had to tune them to suit. So I had to remove the nacelle and dismantle my unit several times to adjust the spring tension on the emulator to get a setting that I was happy with. But since then I have been very happy with the improved fork damping.
On the rear of the swing arm bikes I use Koni / Ikon shocks. The Ikon dial a ride shocks are very good. When my wife is pillion I up the spring rate one notch and increase the damping one click on the dial. I had a problem with cheaper shocks wallowing and bottoming out so I fitted slightly longer Ikons. The better damping of the ikon would have stopped the bottoming out but the extra ground clearance also improved ground clearance when cornering.
David

[allan.walker]

Food for thought, thanks, David.
I have a Huntmaster-framed Square Four and the forks seem to be rather crude in operation (compared with my Commando and Matchless G11.)
It looks like some form of upgrading is on the cards...

Regarding the rear suspension units, how much longer than standard Are your Ikon units? Ground clearance whilst cornering is another shortcoming that I would like to improve.