It’s funny how things get started. But how could a thing like this happen.. and what is it?! This episode happened and was written-up around the Christmas of last year, which is why it has to appear today, to avoid an extra year of delay!…
I have a little friend called Ezra who is 1, and he took me, with his parents, uncle and aunt and grandparent Helen, to a Christmas lantern workshop in Pontypridd. Ezra’s mum Ally made an owl:
Now if Ally was making an owl, what kind of creature could I make? What else of course but a volant dromaeosaur – a vodrom 🙂 . That is, a flying example from the group of dinobirds to which Velociraptor belonged. Velociraptors were flightless descendants of flying forms, from which modern birds were also descended. Astonishingly, no physical representation of a vodrom with its rear wings in the only sensible flight configuration it could have used, has ever been made…until now!
So we’re talking part Christmas decoration, part science project.
So fast did I work that by the end of the first two-hour session, I’d already stuck fourteen sticks together, if the image below, taken upstairs at Pontypridd library, was taken near the start of the second session. I would say in my defence that we were late for the first session, and I took the trouble to split the ends of all six sticks in the front and rear triangles so the ends of the withies could be interslotted across each other to some extent, before being masking-taped.
I can’t remember much about the second session except for a couple of interactions. A little boy walked confidently in and made a bee-line for my design sketches, and of course I told him Don’t Touch That!! The lady in charge, Angharad I think, immediately summed up the situation and suavely and expertly ushered me to the far end of the table where I would have more room or something, but where of course the strange man would be less of a threat to the smaller children. Whilst there, a baby and her mum sat next to me, and the baby became absolutely fascinated by the resonant and strangely sinister sliding tones the strips of masking tape made as they were peeled of the reel 🙂 .
In the third two-hour session pretty well all I did was make the rectangular feet, out of willow withies, the left of which is shown on the table in the image below.
And that didn’t include the foot feathers which already appear in the pic above, thin garden canes forming their edges. The foot feathers are largely attached to, and obscuring, four pieces of thin cane across the end of the foot.
The inner sections of the front wings are part of the carcass, and each has four visible twists of thick wire hanging down, connecting to points on the outer wing sections when those are lifted into place from below. The front wings are set in the position just before they reach the end of their upward travel. The rear wings are 90° ahead of the front wing cycle, as justified in The Secret Dinobird Story, and as is the case with dragonflies. The rear wings, when attached, are about half way through their “downstroke”. However, whereas the whole of the front wings goes up and down as in modern birds, the rear wing power stroke is largely provided by the feet which push out first then down, aided somewhat by the shin section i.e. tibia & fibula, which also bend out and up a little at the knee to provide an overall straightening of the leg. Just possibly the thigh bone i.e. femur contributed too. This leg straightening would utilise the same muscles used by these creatures in the stabbing motion (not really slashing, note) of the leg and big toe claw, which was their main offensive feature. Since their teeth were rather thin and pointed backwards more sharply than in other predatory dinosaurs, they would have been broken or twisted out of their sockets if used on the prey in anything other than clean backward slices through dead meat, and to guarantee this, the prey must have already been dead at the time. That’s how we know the toe claw (or something other than the teeth – and there is no feasible alternative) was used for killing.
The image above shows a very important feature of vodrom aerodynamics: the skirt behind (in this pose, below) the rear legs. The rear wings are rooted very high on the body – they stick out sideways from the hip sockets which are quite high in the pelvis. (This allows the legs to be longer and have longer strides than if the hip joint was lower.) However, very unlike modern birds, vodroms had shoulder sockets quite low down in the body. This might have been connected to the need to reach out and grab their prey with their arms, preparatory to using the big toe claw, and the prey would usually be effectively “ventral relative to” the dromaeosaur’s chest, though it may have been lying on its side. Anyway, the root of the rear wing was quite a bit higher than the root of the front wing, and to streamline this and avoid the rear leg offering a massive air-break to the oncoming airstream, some kind of surface, a “patagium”, made of stretched skin and feathers, as appears in front of the elbow of an extended modern bird’s wing, would be expected to be present between the root parts of the front and rear wings. As with that wing patagium in modern birds, it would be angled down at the front, and on its own would give negative lift. However, in the modern bird case, behind the thicker part of the limb, a trailing-edge surface comprising two thirds or three quarters of the rear section of wing, would be angled down towards the back, and both on its own and combined with the front part of the surface, would provide lift at the rear. For this reason alone there would probably be a substantial skirt behind the rear legs. Some parts of the leg might be quite thin but the main muscles for moving the legs would have to be somewhere, inevitably in the thigh and just below the knee . Interestingly the lower half of the shin bone (tibia) is incredibly thin in the presumably volant dromaeosaur Bambiraptor, even though the top half is pretty thick.
The skirt would have to be unconnected to the tail which flicks energetically up and forwards over the back during the toe strike, a movement which was the whole raison d’être of the special long stiff tail. The feathers forming this skirt would have to swivel round the leg when the knee was angled forwards for walking, otherwise they would stick out to the side. This must have evolved before dromaeosaurs though, because the toes-and-knees-out pose used in flight by dromaeosaurs was used even in the gliding stage of their ancestry. A massive change of angle would have been especially necessary for the primary feathers on the foot of course.
At the extreme right of the main carcass in the photo above, at the end of the shin just above where the ankle will go, there are four thin little green cane sections in parallel. When the foot is attached, sticking upwards and outwards at right angles, these green canes are used to snag the free ends of lengths of fishing line, one for each foot feather, attached to the far end of each feather. When tightened, this applies a slight inward bend of the feather tip, as would be expected when the feather was pressing down against the air in the power stroke. Ideally, this bend, incorporating also the resultant forward thrust which would actually exceed the drag caused by the downward movement through the air, would also bend the end of the feather forwards.
A little forward and upward bend has been achieved, enough to suggest the force and movement involved. Unfortunately, tightening the fishing line beyond a certain point results in the concentration of bend towards the middle of the feather becoming rather obvious. In life the bend would be pretty constant in the outer half of the feather because the feather is more flimsy towards the end, to compensate for the tendency of the bend to be greater towards the middle. This could have been effected in the model by adding short splints to the base and middle of the feather canes to apply extra stiffness but by that time I couldn’t be arsed. It has been possible to twist the foot so that the plane of the feathers is slanting, to show how forward thrust is produced, but the reverse twist of the end of the feather to provide thrust during a firm downstroke, as opposed to the normal angle during gliding, which provides lift, has not been effected. Some effort was made to produce this by attaching the end of the fishing line to the rear edge of the feather, but it didn’t work very well and I even forgot to do it for two of the feathers.
Initially the fishing line was wound onto sticks with cross-pieces (shown in the image before last, furled up at the feather ends for tidy keeping when the foot was detached), and when the foot was connected, line was unwound and the sticks were stuck through the cane grids on the shins, where the cross pieces prevented the sticks rolling and unravelling.
Later, Helen suggested and made hooks out of strips of copper about 30mm long, with a hole opposite the hook end, for the fishing line (which she also provided from her magic shed) to thread through. These hooks were then poked usually over the top “musical stave cane” and hooked over a lower one. By this stage the extra lengths of unwanted fishing line could be cut off, now the approximate length was well known, and any minor adjustments effected by the choice of which stave lines the hooks were poked through and hooked over. Two of the now sad little t-sticks are seen lying unwanted beside the scissors, in the image above.
Helen papered the feathers of the right foot and did it just twice as fast as I took to do the left foot, and better. Also visible in the photo above is the fillet of red leather Helen kindly mended my slipper with. Ezra, who is her grandson, was fascinated by this red flash, and would bend down, carefully grasp it, and try to lead my foot in the direction of the room where he wanted me to go.
The photo above illustrates a slight problem of scale that eventually developed. When I made the first little triangle for the shoulder region, it was only about 30cms wide. I think I imagined subconsciously that the whole thing would be just over a meter wide. But it turned out to have a wingspan (a double wingspan of course) of about seven feet, and was about eleven feet long including the tail. It had to be built in sections (seven of them) just to get it in the car.
Among many other songs, “Jingle Bells” was sung, and the words were shown on a screen. At last I was able to get to the bottom of what that mysterious line “…Jingle bells, jingle bells, there’s sailing on tonight!” was all about. Actually, the line is:
“What fun it is to ride and sing a sleighing song tonight!”
That’s good, because I never could work out what sailing had to do with Christmas, and as my mis-heard version suggested we would all go home and watch sailing on TV, when even as a kid I thought the song must have predated TV, that is also resolved.
But did you know the song included this verse?:
“A day or two ago I thought I’d take a ride
And soon Miss Fanny Bright was seated by my side.
The horse was lean and lank, misfortune seemed his lot,
He got into a drifted bank and then we got upsot!”
Hmm. Reminds me of that scene with Flashman in The Great Game where he had to look after the girl after a sleighing accident.
Towards the end of the proceedings in the church, it was announced that the lanterns could be bought for a £2 donation each. Luckily no-one tried to buy the vodrom.
We got it home and hung it from the ceiling against the wall:
I am very proud of this picture below. The background distractions of the original photo have been blanked out: