Headstock Mods and Alternatives

[Oldhaven]

I hope I am not getting too far off track from Carbon fiber parts, but thinking of advanced materials to save weight reminds me of an exercise I did a couple of years ago. I was looking at alternatives to a bent UFM I was dealing with.

http://www.vincentownersclub.co.uk/...ad-for-d-continued-technical.7122/#post-56807

While I initially did this design for machining from aluminum billet, I did some blue sky corresponding with davidd about creating a head lug in other materials. Technologies such as laser sintering can create these things straight from the solid model. I also did some design modifications to account for the much weaker materials. I did not have FEA software capable of doing an analysis and this was more for fun than anything else and went nowhere. I looked at different materials for this model and found:




The model when realized would weigh the following in different materials (Pounds):



Steel 11.1, titanium, 6.1, aluminum, 3.7, duraform nylon 1.4, carbon

glass filled nylon 1.2, Windform 1.53. The composite/nylon materials

would not be suitable for this design as first modeled of course, and would need some

added metal sleeves for bearing pockets and through bolts and more reinforcement, but the design I did adding them to the design

would weigh 2.17 in duraform, 1.85 in nylon /carbon/glass, and 2.36 in Windform, still less than a metal

headstock after adding a lot of material, and all of them under 3 pounds

with the metal inserts. the real question is whether the

nylon/composite would be strong enough, even with metal sleeves and

added reinforcement by design. Steel is about ten times as strong as

nylon/composite, (and aluminum is only half as strong as steel, and

titanium is about 80% as strong as steel.)

The weight savings would be considerable over the originals, especially the later versions that do not use the hollow cast tube design. I can't remember or find what mine weighed when it was removed from the tank, but it was a lot more than 3 pounds. I am sure the steel originals would stand up to a crash better, but the real question is whether the design would stand up to everyday street use or racing. Probably yes for the first and no for the latter. At least nothing I would trust my life to.

Ron

 

[Oldhaven]

That link is not very good, but here is what I meant. I was thinking of a hybrid fork arrangement that could have added some rigidity to the front head lug mount:

 

[davidd]

That would be a copy of FT1/4. I think it is quite a nice design. Ron wouldn't fire up his 3-D printer and make me one, though. I think it is a worthwhile part to replace since I have yet to find one that is not bent, although the bending does not seem to hurt the handling significantly.

I have the stock FT1/4 at 7.57 Lbs. The aluminum one I made, which is considerably sturdier (400% greater wall thickness, for example) weighs 4.32 Lbs., saving about 3.25 Lbs.

For me, high strength aluminum was the only choice I could make and get the project done. The original is cast steel, so it was relatively easy to save weight and add strength. I do not have the expertise to cut the weight in half again.

David

 

[Black Flash]

Hello David
from the picture of your alloy headstock it looks to me like you have bolted the tank to it using bolts (setscrews.. I never know the right expression in English).
Am I correct? just tapping the holes and fitting it with screws instead of through bolts?
I am just asking because a friend told me he could not supply the right strength of through bolts as they were a very critical part on the bike.
so if your mod withstands the rigors of racing could I also use standard grade stainless through bolts?
Bernd

 

[davidd]

Hello David
from the picture of your alloy headstock it looks to me like you have bolted the tank to it using bolts (setscrews.. I never know the right expression in English).
Am I correct? just tapping the holes and fitting it with screws instead of through bolts?
I am just asking because a friend told me he could not supply the right strength of through bolts as they were a very critical part on the bike.
so if your mod withstands the rigors of racing could I also use standard grade stainless through bolts?
Bernd

Bernd,

The headstock is done with through bolts. The holes through the headstock are reamed to 5/16". I have used grade 8 bolts in the photo which have a shear capability of about 4500 Lbs. each and tensile strength of 8700 Lbs. I think that is the equivalent of the strength of the originals. I think the difficulty with the originals is finding "off the shelf" countersunk nuts and countersunk bolt heads. The Factory most likely made the mods to the fasteners themselves. The objective was to make good alignment between the two pieces to prevent movement. The problem with Grade 8 bolts through bolts is that they should be modified to fit the countersinks. I have not made a decision about the fasteners yet. I have to pass it by the machinist.

Grade 5 would have a tensile strength of 1700 Lbs. less and Grade 2 would be about 4300 Lbs less than the Grade 8 mentioned. I assume that the stainless hardware supplied by the Club is Grade 2 or less, but I do not know for sure. Grade 2 is usually what one finds in the local stores in the bins.

I have stayed away from stainless on the racer. Most steel can go through tens of millions of cycles before fatigue breaks. Most stainless is not close.

Traditionally, the UFM nuts and bolts have not been available for sale. The steering head was not supposed to be separated from the oil tank. At this late date, many of the UFM's I have are already separated or have replacement bolts that have been bodged.

I would not use stainless nuts and bolts on the headstock, but maybe these special items are available now from someone. I would be interested to hear about what others have done.

David

 

[champion]

The Irving Vincent headstock which won at Goodwood in 2015.

 

[Oldhaven]

That looks like an original one used as the basis for some added bearing arrangement, and an early one to boot since it has the welded up reinforcing straps rather than the later one piece straps. I can even see the foundry or casting mark on it. I thought Irving Vincent's used an all new welded UFM? Maybe that was not allowed in this race.

Ron

 

[davidd]

That looks like an original one used as the basis for some added bearing arrangement, and an early one to boot since it has the welded up reinforcing straps rather than the later one piece straps. I can even see the foundry or casting mark on it. I thought Irving Vincent's used an all new welded UFM? Maybe that was not allowed in this race.

Ron

Ron,

The Irving Vincent does use a new UFM, but that is a photo of the Horner's Vincent at Goodwood. To meet the rules the Horner's had to build and original bike. The Irving-Vincent uses a copy of the original welded UFM. As I understand it, the original design was a welded sheet metal UFM, but they were not able to get consistent alignment due to the heating during manufacture.

I think the prototype was relegated to dyno duty as and oil tank. Here is the Irving-Vincent:

David

 

[b'knighted]

I would be interested to hear about what others have done. David

I consider the design of the countersunk nuts on studs to be a weakness. The factory must have thought so too as they improved the system on the D by using a single stud with plain nuts.
I have seen B/C studs sheared just inboard of the countersunk nuts and many of the UFMs I've handled have rounded, stripped or loose nuts, despite the staking.
I needed to repair one and didn't like the original system or the total price of a full set of new studs and csk nuts at about £70 each.

I considered that the part of the assembly needing most strength was at the outboard end of the studs where the core diameter is reduced by threading. My alternative was to replace the stud & nut system with two plain shanked stainless bolt blanks with their heads countersunk. These are drilled and tapped, about M5 if I remember correctly. Once again from memory, a 30mm grub screw was screwed though until 15mm protruded then locked with another grubscrew. This then allowed the two shanks to be screwed together through the headstock bore using a spanner on the hex. The second side was then locked with a third grubscrew.