Head steady?

[LaceyDucati]

I saw a mention earlier in this thread about my use of a head steady. We did use one on a 350 but to be honest it actually upset the handling and after some time of trying to improve things with different set-ups, we restored the handling by removing the head steady! Generally we have found although the standard frames are not particularly stiff designs, because of the bikes lightweight and good geometry they handle well. Yes, they flex about but they still go through the corners. Another thing to bear in mind is that bracing the head will potentially effect vibration issues and lead to the need for a different balance factor. I have found this to be the case when running the same engine that runs sweet in a standard frame that will vibrate significantly when bolted into a saxon race chassis.

There is plenty of scope for stiffening the swinging arm and we have always braced the end of the swinging arm fork round to avoid flex and breakages as already mentioned by Eldert on another thread. Latterly we also made new swinging arms, 35 OD 2mm wall thickness, again much as Eldert has already mentioned. For the road, I don't really think many of these problems would come to light and mods would be mainly for the pseudo race look

Nigel

[DewCatTea-Bob]

By: LaceyDucati...
" I saw a mention earlier in this thread about my use of a head steady. We did use one on a 350 but to be honest it actually upset the handling
we restored the handling by removing the head steady! "

____ I'm fairly surprised that further use of the motor as a stressed-member within the frame would actually stiffen it up so as to have a NEGATIVE-effect on handling ! _ Perhaps nonDUCATI riders who've never become used to the manor in which std.Dukes handle, would have a different opinion if they started-out on the modified version, and THEN had the head-steady bracket removed ?
(Just trying to make some sense out of the results.)
__ Do you happen to have a picture showing the design of your tested-out head-steady bracket, installed on a frame ?


" Another thing to bear in mind is that bracing the head will potentially effect vibration issues and lead to the need for a different balance factor. I have found this to be the case when running the same engine that runs sweet in a standard frame that will vibrate significantly when bolted into a saxon race chassis. "

____ Seems understandable, since different frames ought have different resonate-frequencies (to intensify vibration at).


Hopeful-Cheers,
-Bob

[LaceyDucati]

Bob,
Stiffening the frame by using the engine as a stress member of course should improve the handling which is exactly why we did it. The result was that the rider lost feel in the bike and ended up with things getting all out of shape. We persisted for a couple of meetings making slight changes to suspension but at the end of the day removing the head steady returned things to as before. That's not to say that adding a head steady may not improve another machine but we couldn't simply resolve the issues with this machine and there comes a time when you have to forget the theory and get on with racing. It is widely recognized by experts that there is an element of "feel" in handling as it is perceived by the rider that cannot actually be quantified. This rider is very experienced and has raced a wide selection of motorcycles from many periods. However, that said, I did convert another bike at around the same time and that bike is still braced with no reported problems, mind you that rider is not in the same league and hasn't achieved the same results.

Unfortunately the work was carried out in a period when we were interested in doing things rather than recording them for general interest and also prior to us owning a digital camera! The bike has also now been sold on so cannot retrospectively photograph it. The head steady was constructed by inserting a boss horizontally through the frame tube above the cylinder, this was tig welded in place. Two mounts were fixed to the head under the slightly extended head bolts. In between the head bolt holes on the mounts were 10mm threaded bosses. A triangulated bracket formed the steady bolted to the engine via the threaded bosses and to the frame via an 8mm bolt through the newly installed frame boss.
Hope this makes sense,
Nigel

[Jordan]

Nicely described, Nigel - thanks.

I guess there are 2 types of head steady - ones that are very solid like yours which strengthen the chassis, and ones that are simple lightweight links that prevent resonance but don't do much to change the frame rigidity.

Jordan

[graeme]

Wonder if a Commando spring type head steady would change the lever rattling vibrations?

Graeme

[Jordan]

Wonder if a Commando spring type head steady would change the lever rattling vibrations?

Graeme

That should be easy to organise. Why not give it a go?

[StewartD]

Hi Graeme,

The Commando has a full rubber mounted engine, gearbox and swing arm. The spring head steady is working in conjunction with the rubber 'Isolastic' mounts at the front of motor and to the rear of the gear box. These mounts allow the engine/gearbox/swingarm to move to quite a fair degree in the plane of the machines centreline. The Isolastics are designed to limit any movement transverse to this plane, which would result in terrible handling. A properly set up Commando handles pretty well. If you see a Commando at idle, the movement is quite significant. From memory it is about 3 - 5mm.

I'm not any sort of expert on Commandos, although I did have one in the 70s which I started my road racing on. That said, I assume that the spring head steady is to allow more equally distribute the load between the two Isolastic mounts or limit extreme movement. It is not there to prevent vibration! A Commando functions very well with this 'controlled' vibration and is very smooth to ride.

I'm sure that using a Commando head steady would not make any difference to a conventional, (rigid mount engine), motorcycle's vibration as it is designed for a different engineering problem than simply increasing rigidity.

I think the best course of action is to check the vibration of other people's Ducatis and compare. I had a disc brake 450 which a did many touring miles on. I was never too worried about the vibes, but I think the earlier 450s had a different crank which may have had different characteristics. If you think your model is exceptionally bad, then I think getting the crank balance checked would be an easier course of action than adding head steadies. Also, checking the tension of engine mount bolts is worthwhile first step. Make sure they are either the genuine Ducati bolts, or that they are at least grade 8.8, otherwise they just wont be strong enough, especially on the narrrow crankcase models. For more on bolt strengths and the engine mounting, check my post of April 13th, 2013 in the thread '250 Street Scrambler'

By the way, I think you are in Oz; if that is so, are you going to the classics at Phillip Island this weekend?

Good luck,

Stewart D

[Nick]

Engines need room to 'grow' when they're running and heating up. I was told by the owner of Trackmaster that their Yamaha 750 engines put out more power without the top motor mount. He suggested using a heim joint that prevents front/back movement but allows the engine to move vertically.

I know a professional bike builder who drills out all his motor mounts in the cases and frame to fit slightly oversize bolts to ensure a tight fit between engine and frame. If you look at the amount of slop between typical Ducati single engine mounting bolts and the frame, plates and engine, you'll see how much room there is for improvement in this area.....

[LaceyDucati]

I always used 3/8" bolts in the rear mounts of our narrowcase race bikes. I also used special bolts to make sure the plain section of the shank protruded through the frame plate so that the thread did not run in the frame plate. I then used a thick spacer washer to ensure the bolt tightened without bottoming. Apart from the lower engine dowels, there was little opening out holes to fit the 1.5mm larger bolts! So yes there is alot of slop in the engine mounts

Nigel

[Jordan]

Good point about threaded bolt through the frame plates being undesirable.
Phil Irving recommended at least 50% unthreaded in plates. Using spacers sounds like a good idea too, can get 100%.

A reamed fit for engine bolts is not so much for vibration control, more to improve rigidity and handling of the diamond frame I think.
Being such a close fit, could they get stuck?