FF: Forks Steering Damper: How To Drill Holes In FF2 Without Dismantling The Girdraulic Fork.

[CarlHungness]

Isn't a tank slapper known to the engineers as a 'dynamic coupling' whereby a confluence of forces (i.e. sideways, up, down, angled) come together to create the tank slapper itself. I recall seeing a 'speed bump' in a parking lot one day and something told me to try and initiate a tank slapper at low speed. Thus I rode over the bump at about 5-10 MPH, literally slapped, or jerked the right handlebar, and sure enough, the bars started to wobble...fairly violently, at as low a speed as I could maintain the bike upright. The 'slaps' happened for a couple of feet, but I was able to ascertain that under the right conditions the tank slapper can occur. I don't recall if my steering damper was 'just-biting' or if I had it loose. Ever since I know I have kept the damper a bit tighter than just biting, and if I see I am about to run over a pothole my whole upper body gets stiff as I'm locking my arms onto the bars. Thankfully, I've never had a tank slapper, other than the day I bought the bike. I was riding home 30 odd years ago on the 'freeway' , the speedo cable broke and I foolishly said, "Crap, and slapped the speedometer! The bike went into a slapper, right in front of a huge truck. As I recall it was going down to the right, and as I opened the throttle, it seemed as though I was able to wrench it back upright without going down. The incident scared me so badly I parked in a truck stop for a couple of hours. A trucker came by, talked at length, and we loaded the machine onto his truck and he drove me the next 100 miles to my destination. I avoided disaster and this was after riding the machine about 250 miles or so. I think any two-wheeled vehicle can go into a tank slapper under proper conditions. Remember, my test was done by going just about as slow as one can go and still keep the bike upright.

 

[CarlHungness]

I made some improvements to the text of post #1 in particular to the thickness of the spacer.

I copied the first text...where are the improvements posted?

 

[Paul Coene]

About the thickness of the spacer between steering head and stainless plate. (If indeed you copied the first text, it shoudn't be to diffcult to find the modifications, though ?)

 

[timetraveller]

Some comments about Carl's posting above. First, friction dampers. When was the last time anyone produced a new vehicle, 2, 3, or 4 wheeled, with friction dampers on the suspension? Vincents used friction damping on the front and rear suspension on the 'A's but changed to hydraulic damping with the girdraulics. At the rear they still used a combination of hydraulic and friction. With the 'D's, 1954, they finally realised that hydraulic at the rear was sufficient. Why then would anyone consider that friction damping would be more than adequate for the steering. The old adage of lots of stiction and not much friction is well applied to friction dampers. When I had my 'big off' at Cadwell the friction damper was well screwed down and it might as well not have been there.

Next the difference between a wobble and a 'tank slapper'. The fact that Carl was still able to hold on to his throttle suggests to me that it was not a real 'tank slapper'. It might depend upon the speed of the bike and rider but at 100 mph a combined weight of bike and rider of, say, 600 lbs gives lots of kinetic energy to be fed into the oscillations. At much lower speeds then perhaps not so much. I could not have continued to hold on to the handlebars had I been a Mr Universe type character. If one wishes to keep the bike looking as near as standard then I can see the reason for staying with the friction damper. I still think that if one wants the safest and most comfortable system then the JE stem etc, is the way to go. I designed the hydraulic damper kit for the standard set up to be as inconspicuous as possible by placing it across the bike, rather than fore and aft. I did make one batch of twenty to keep the price down to £100 per set but one gent decided that was too much so he made five similar systems for his own use so it is possible.

 

[Bill Thomas]

I see the Kawasaki style Damper has gone up to £87, Not sure if VAT is on top, Don't think so ?.
From M and P Swansea.
I think all bikes should have an Hydraulic damper.

 

[Paul Coene]

I did make one batch of twenty to keep the price down to £100 per set but one gent decided that was too much

there's always someone who does it cheaper.