New use for a Kibblewhite Performance valve spring (2013)

Only three hours from home, I think that almost counts as all the way!

Glad you made it home, sorry the bike didn't make it all the way.[/quote]

+1 I think that's pretty darn close too

Jim did a few 1000 miles so he got pretty close but still more like flying an orbiting rocket thrust supported lander than breaks down only 3000 ft above the ground, so must bail out and parachute rest of the way to be picked up by rescue crew. If it can happen to him it could happen to any of us and does.

I know this is an old thread but I'm really curious how that kibble white spring set up held up long term? Do you have any more photos or perhaps drawings of the brackets? I'm quite surprised this mod didn't catch on!

Cheers
Dan

I am still running the same spring and loving it. Jim

comnoz said:

I was just thinking of the head steadies I have had on my EFI bike.

1. the original -it cracked

2. original replacement - it cracked and one of the side plates cracked.

3. an Isolastic type - I don't remember who made it but it transmitted way too much vibration to the frame for my liking. It had pretty firm rubber donuts in it.

4. Another isolastic type that I built with no rubber donuts. I used Teflon washers for side to side control. The washers were short lived and would pound out in a few hundred miles.

5. The Dave Taylor headsteady, it actually worked pretty well, my only complaint was wear in the joints after long rides in the rain. The road grit and water got into the joints and made them loose and squeaky.
I eventually took it off and installed it on my racebike and it broke when I crashed at Gratten.

6.That is when I made my own headsteady with sealed tie rod ends. Close to 50,000 miles now and it is as tight as the day I installed it. Jim

Click to expand...

A very nice peice of engineering Jim
I recently removed a norvil type head steady ive had for years and thanks to Holland Norton Works
I replaced it with a Comstock H/S

comnoz said:

I am still running the same spring and loving it. Jim

Click to expand...

Ah great to hear!! I have a machinist friend lined up to weld in a cross brace up front and would love to include a bracket for this. Do you have any measurements or angles I could work with?

When Jim was doing my Fullauto head I asked if he wouldn't mind me copying this idea. He was fine with that & so I made & fited it to my 920. It is fantastic as the bike is smooth & the front ISO gets a much easier time. i.e. it doesn't get compressed & start to collapse over time. This is what the original half arsed lash up was supposed to do.

Martyn.

In the photo there is a cross piece welded into the iso holder and a pod shaped thing bolted in. There is another one mounted on the right downtube, also in the same picture. Any idea what that is and it's function?

Jim
You we’re on your way to the Wyoming rally when you first posted this?
We talked there.
David

Matchless said:

When Jim was doing my Fullauto head I asked if he wouldn't mind me copying this idea. He was fine with that & so I made & fited it to my 920. It is fantastic as the bike is smooth & the front ISO gets a much easier time. i.e. it doesn't get compressed & start to collapse over time. This is what the original half arsed lash up was supposed to do.

Martyn.

Click to expand...

Can you share any photos you have, of course if Jim is ok with others copying his design??? Jim?

Sorry but I haven't got a clue how to post pictures. It looks the same as Jims but has a screw adjustment. Very simple to make.

The idea of a third ISO mounting has existed a long time. Jim's solution works a little different as it has no damping characteristics.
Frame attachment may be achieved without welding or brazing by using a transverse bar bolted in clip-on style.
For a durable solution enduring the elements, I propose fitting a spring encapsulated in soft rubber, as in one block.
Which spring rate does your spring have, Jim? It has to be fairly soft. My first guess is a spring rate of about 60 N/mm (343 lbs/in ) which equates to a spring of 40 mm length being compressed 30%.
By clever design, no spring compressor will be needed. Spring (block) may be prestressed by a moving lower support plate. This allows for an accurate weight balance.

-Knut

Here is the spring specs I have, There is a small amount of damping from the dual spring setup.

Here is a dirty shot of the installation [lots of miles on it now]. I powder coated the spring before I installed it.
There is no rubbers or iso shims in the front mount. Just a spacer and a couple plastic caps to keep the dirt out.
The spring is easily removed by removing the long front mount bolt, this allows the motor to be raised just far enough to remove the spring.
The tie rod link keeps the front of the engine from moving side to side [like the original iso shims did -except the rod ends don't wear out quickly] This mod was done long before the spring mod.
Spring free length is 4.5 cm
Length as mounted is 3 cm

Jim,

Your spring rate is rather low: (185-105)lbs / 0.5 in = 160 lbs/in == 28 N/mm. Assuming a linear spring rate, the gravity counteracting load is F=28 N/mm*(45-30)mm = 420 N which equals a load opposing gravity of
420/9.81 = ~43 kg. It's on the low side, don't you think? I proposed a stiffer spring, negating weight of the complete engine/trans assembly, and I was just guessing the total weight to be around 80 kg. This spring load should be placed right beneath center of gravity of the engine/trans assembly.

-Knut

mdt-son said:

Jim,

Your spring rate is rather low: (185-105)lbs / 0.5 in = 160 lbs/in == 28 N/mm. Assuming a linear spring rate, the gravity counteracting load is F=28 N/mm*(45-30)mm = 420 N which equals a load opposing gravity of
420/9.81 = ~43 kg. It's on the low side, don't you think? I proposed a stiffer spring, negating weight of the complete engine/trans assembly, and I was just guessing the total weight to be around 80 kg. This spring load should be placed right beneath center of gravity of the engine/trans assembly.

-Knut

Click to expand...

My spring is under the front of the engine. The rear of the cradle is supported by the original rubbers in the rear mount.
Most of the engine motion is in line with the cylinder. This makes the cradle pivot around the rear mount.
I tried 3 different springs. This one worked out the best.

deleted.

mdt-son said:

Jim,

Your spring rate is rather low: (185-105)lbs / 0.5 in = 160 lbs/in == 28 N/mm. Assuming a linear spring rate, the gravity counteracting load is F=28 N/mm*(45-30)mm = 420 N which equals a load opposing gravity of
420/9.81 = ~43 kg. It's on the low side, don't you think? I proposed a stiffer spring, negating weight of the complete engine/trans assembly, and I was just guessing the total weight to be around 80 kg. This spring load should be placed right beneath center of gravity of the engine/trans assembly.

-Knut

Click to expand...

Knut
When I installed the Mk3 spring on the top iso I measured the force required to achieve "loose/sliding" on the lower front iso bolt. That means that the front iso should no longer be taking any substantial vertical (or fore/aft horizontal) load. That value was 43 kg.
here's the link : Feb 13, 2021
The effort was purely empirical - I was surprised at how low that force was.
Cheers

Rob, Thank you for your information. Gravity load of the powerplant is basically carried by the front and aft iso mounting only. The top mounting is not designed to take gravity loads and the headsteady spring on the Mk3 is a misconception trying to patch up a design shortcoming.

The load you introduced is in proximity of the front iso mounting in a vertical-longitudinal 2D plane, so it tells approximately how much gravity load goes into the the front iso mounting. What it doesn't tell is how much load goes into the rear iso mounting. If we assume the CoG point to lye at say 35% of the length between these two mountings, then the rear iso mounting will take (35/100)*43 kg = 15 kg only. If my assumptions are correct, the entire powerplant weigs (15+43) = 58 kg. That figure appears too low to me - I had assumed 80 kg but that's probably too much. Deriving at the exact load distribution requires gross weight to be weighed and the dimensions between support points recorded. Did N-V ever issue a drawing of the powerplant showing dimensions between the 3 support points?

In the meantime I have found that gravity balancing is of little interest. The inertia and gas pressure forces are huge in comparison, but they are peaky depending on rotation angle of the crankshaft. Therefore it's difficult to know which load to counteract. A hard mounting would be best, but hardly in the interest of shielding vibrations from the rider! Of course twin balancing shafts would solve the problem .....
Looking into how inertia and gas pressure forces act on the iso mountings is necessary. What does the extremely high peaky loads do to the rubber mountings?

-Knut

mdt-son said:

The top mounting is not designed to take gravity loads and the headsteady spring on the Mk3 is a misconception trying to patch up a design shortcoming.

Click to expand...

I have a cNw head steady and the MKIII spring which is yet to be installed. Are you saying that the spring is a waste of time?

The stock MK3 spring setup sure works well to eliminate vibration . It also keeps the front ISO from sagging, which is likely the cause of some vibration in bikes without the spring.

Set it up as RobSS mentioned, all weight off the front ISO, bolt free to slide.
With that setting the bike should be a real smoothy above 3k rpm.

Glen