秋田県角館の祭礼である飾山囃子（おやまばやし）の山車（ヤマ）の曳きまわしは，ヤマ同志を激しくぶつけ合い，さらにはヤマの前部フレーム（舳先）を押し付け合ったまま前輪を浮かし，ぶつけ合いを継続したまま，それぞれのヤマと，それを操作する人々やそれに搭乗してお囃子を演奏している人々の“力・強さ・プライド”を競い合うゲーム性の高い祭礼の一つである。
The pulling of the floats (oyama) of the Oyamabayashi Festival in Kakunodate, Akita Prefecture, is a very famous traditional Japanese festival in which the floats compete with each other by raising their front wheels and repeatedly bumping into each other. This festival has a highly competitive character, in which the “power, strength and pride” of each oyama, the people operating it and the people playing the musical accompaniment on board are pitted against each other while they continue to bump into each other.
by Professor Hidehiko Tsubogo, by Ymaguchi Univ.
このゲームに勝つために，継続的な知恵や工夫の絞り会いがヤマの形に蓄積されていると考えられる。丁内組織と若者組織の作戦の上にヤマが町中を動き､ぶっつけられるので、その構造は頑丈でなければならない。民俗学的調査においても，町の大工を中心に形に改良が加えられてきたことが明らかになっている。
In order to win this game, the continuous squeezing of wisdom and ingenuity seems to have been accumulated within the very form of the oyama. It is essential that the structure is sturdy as the oyama moves around the town and is repeatedly bumped into. Only then can the best oyama win following the rules of the game, under the watchful eyes of the chonai (local area associations) and youth groups. Some ethnographic researches have also revealed that the forms of the oyama have been continuously improved up to now, mainly by the carpenters who lived in each local area.
ここでは，この歴史的なゲームに勝つために時間とプライドをかけて蓄積されてきたヤマの形・構造に見られる工夫やアイデアに光を当ててみたい。
Here, I would like to shed light on the ingenuity and ideas found in the shape and structure of the oyama, which have been accumulated over time with pride to win this historical game.
- 1. 秋田県角館町「飾山囃子（おやまばやし）」The Oyamabayashi Festival in Kakunodate, Akita Prefecture
- 2. ヤマの構造 Structure of the yama
- 2. ヤマの構造 Structure of the yama
- 3. ヤマの変化 －横町ヤマに見る構造の変化 Changes in the float – the structural changes in the two floats of Yokomachi
- 4. ヤマの形の必然性 Conclusion
1. 秋田県角館町「飾山囃子（おやまばやし）」The Oyamabayashi Festival in Kakunodate, Akita Prefecture
日本民俗学会の機関誌 『日本民俗学』 77において，中村孚美氏が発表した「町と祭りー秋田県角館町の飾山囃子の場合」によると，この祭礼を構成する要素は(1)丁内（町を分ける区画）同志の対抗 ， (2) しきたりを踏まえた山車の曳き回し， (3) （若者たちが）参画する祭り，(4) 頑丈な山車の構造，の4つに集約されるとされている。そして，この祭りを計画し，運営，実行する“若者”を引き付けてやまないものは，この祭りシステムのゲーム性と肉体的な“ぶつかり合い”であるとしている。3日間にわたる祭礼の最終日のクライマックスではこの山車（曳山）の参画者のプライドを掛けた本物のぶつかり合いにより相手の山車を壊すところまで勝敗を付けようとする。
According to “Towns and Festivals: The Case of Oyamabayashi-bayashi in Kakunodate-machi, Akita Prefecture”, published by Nakamura Fumi in the journal of the Folklore Society of Japan, 77, the elements that make up this festival can be summarised as (1) rivalry between townships, (2) pulling of the floats based on tradition, (3) participation of young people, and (4) robustness of the float structures.
The game aspect of the festival system and the physical ‘clashes’ are what attract the ‘young people’ who plan, organise and carry out the festival. The climax of the final day can be seen as a realistic clash between the floats, in which the participants seem to be eager to win even if it means destroying their opponents’ floats.
ぶつけ合いによる操作性と強靭性をこの山車は必然的に求められることになる。さらには，民俗学的調査によって明らかにされているが，山車を出す丁内（町内より小さな区画）ごとに大工がいて，丁内ごとの総力戦的な様相を呈している。独特なルールの下で制御された丁内の力とプライドを掛けた祭礼が繰り返えされることによって蓄積されてきた地域の知恵やアイデア，思いなどが，この飾山囃子の山車の形に集積しているようである。
The floats are inevitably required to be maneuverable and tough due to the clashing against each other that takes place. Furthermore, as ethnographic research has revealed, there were carpenters in each tyounai (a local area smaller than a normal township) where the floats were preserved, developed, and pushed to the festival site every year. To the people of each local area, the festival became something akin to an all-out war. The wisdom, ideas and thoughts of the local community, accumulated through repeated festivals in which the power and pride of each local area was put to the test under a unique set of rules, seem to have come together in the very form of the Oyamabayashi floats.
ここでは，山車に対する形態分析から，その形に，他に“勝つ”ために結果的に集約してきた構造体への知恵やアイデアを明らかにし，その価値を紹介する。
by Professor Hidehiko Tsubogo, by Ymaguchi Univ.
平成２３年横町若者曳山 Yokomachi Wakamono float
飾山囃子のヤマはもともと100人もの担ぎ手によって移動していた。下図の日本民俗芸術大観より，その当時の様子が伺える。
The yama of the Oyamabayashi were originally each moved by as many as 100 bearers. The following diagram from the Japan Folk Art Taikan (illustrated book) gives an idea of how such a float looked in those days.
中央の大きくそびえたつ山に飾り人形，そして賑やかそうな囃子方が見られる。明治になると，担ぎヤマから下図の飾り山図のように，車輪に変わり，現在に伝えられる原型となっていることが分かる。この祭りのビックイベントである山車同志のぶっつけは江戸時代から自然発生的に起こり現在に伝えられているようである。若者のガス抜き的な意味合いも強い祭礼だが，けが人だけでなく死者も出ていたようである。それだけに真剣な命とプライドを掛けた祭りとなっていたようである。
The large, towering mountain can be seen in the centre, together with decorative dolls and a lively-looking musical accompaniment. In the Meiji period (1868-1912), wheels were installed under the base to replace the bearers, as shown in the decorative mountain illustration below, and it can be seen that this is the prototype that has been handed down to the present day. The clashing of the floats, a major event in the festival, seems to have occurred spontaneously since the Edo period and has been gradually transformed up to the present day. The festival has a strong element of venting among young people, and it seems that not only injuries but also deaths have occurred. The festival seems to be so serious that people put their lives and pride on the line.
日本民俗芸術大観 第1輯 秋田県角館町飾山囃子記録
The old-style Yama of the Oyamabayashi, from the Japan Folk Art Taikan
2. ヤマの構造 Structure of the yama
飾山囃子の山車のぶっつけにおいて強いとされる横町の山車を一例として，その構造の代表的な，特に山車の運航において必要となる特性に直接的な影響を与える寸法を中心に紹介する。
The Yokomachi yama, which has been considered to be strong in the clashing event, is taken as an example, focusing on the dimensions that are representative of its structure, especially those that directly affect the characteristics required in the operation of the yama.
下図の名称を参照して，主構造は車のシャーシに相当するタテドダイとそれを左右につなぐヨコドダイである。この下部構造からツカ（縦材）とスジカイ（斜め材），下部構造と上部構造をつなぐハシラを介して，山車の中央部を水平に構成するマエダケ，左右のヨコダケ，ウシロダケで構成される四角形のフレーム構造が構成される。この山車の中央に位置するフレーム構造をステージとして飾山（ヤマ），その前部の水屋（囃子方が搭乗する），踊り方の舞台が配置される。角館の飾山囃子の山車の構造において特徴的なのは，この祭礼のクライマックスといえる“ぶっつけ”における衝撃力に耐え，囃子方，踊り子，そして山車自身を守るための工夫を積み重ねてきていると理解できるところにある。
Referring to the names in the diagram below, the main structure consists of the tate-dodai, (longitudinal base frame) which corresponds to the chassis of a car, and the yoko-dodai, (transverse base frame) which connects it to the left and right. This lower-level structure, through the tsuka (vertical timbers), sujikai (braces) and hashira (posts), is connected to the middle level structure that is a rectangular frame structure consisting of the mae-tage (front frame), the yoko-tage (side frame) and ushiro-tage (rear frame) on the left and right, which form the horizontal centre of the float. The frame structure in the middle-level of the float is used as the stage on which the decorative mountain (yama), small room in front of the decorated ‘mountain'(mizuya ) in which the musicians play musical accompaniments and the stage for the dancers are placed. What is characteristic of the structure of Kakunodate’s Oyamabayashi floats is that they seem to have been designed to withstand the force of impact during the climax of the festival (buttuke) and to protect the musicians, dancers, and the float themselves.
丁内を移動する際に鉢合わせとなった山車は，通行権をめぐる“交渉”の後に交渉決裂となるとこの“ぶっつけ”を行いマエダケ同志を激しくぶつけ合い，押し込み合うことを行う。記録によると，一台の山車が前後から二台の山車による“ぶっつけ”の場合もある。この“ぶっつけ”の際にマエダケやウシロダケに掛けられる衝撃力は，このフレーム構造全体とともにスジカイ，ツカを介してタテドダイに伝えられ，前後輪の車軸（シンボウ）に大きな力を掛けることになる。この衝撃力の伝達のさせ方ではシンボウを破損することになり，山車の運航は不可能となり，この祭りのルールでは負けとなり，それぞれの山車を保有する丁内（町をさらに区分したもの）や「若者」（若衆による組織）にとっては屈辱的なこととなる。
The floats meet each other as they move through the streets of local neighbourhoods (cho-nai ). When this happens, if “negotiations” over the right of way break down, the floats that meet each other as they move through the town perform this clash of the floats (butsuke ), in which the front frames (mae-tage ) violently collide with each other and push into each other.
According to records, there were cases where a single float was attacked by two floats, one from the front and one from the rear. The impact force applied to the front frame (mae-tage) and rear frame (ushiro-tage ) during this clash is transmitted to the base frame (tate-dodai) via the braces (sujikai) and, along with the entire frame structure, applies a large force to the front and rear axles (shinbou).
This way of transmitting the impact force damages the axles, making it impossible to operate the floats, and according to the rules of the festival, the floats lose out, which was humiliating for the neighbourhood and the ‘young people’ (an organization of young people) who owned the floats.
また，飾山囃子の祭礼のエリアにある２つの社寺と歴史的な拝礼および旧藩主分家の佐竹家への挨拶のチェックポイントには全ての山車は出向き一連の儀礼を執り行うことが必須とされているが，山車それぞれが所属する丁内以外を通行する際は必ずそれぞれの丁内のとりまとめ役（張番）に許可を得る必要がある。
さらには，一度通行した丁内を再度通行することはできないために，他の山車の動きを読みながら定められたチェックポイントをクリアするためには，“ぶっつけ”を避ける機動性も求められる。この機動性，操作性は前輪と後輪のシンボウ間の距離が影響を与えることは容易に予想できる。このシンボウ間距離が短ければ直進性を犠牲にしつつも旋回性は向上し，“土壇場”での臨機応変な動きも可能となるように思われる。
In addition, all floats are required to go to a temple called Yakushi-do, a shrine called Shinmei-sha and the Satake family seat (home of a former clan branch) as the greeting checkpoints to perform a series of rituals. As they pass through areas other than the local neighbourhood (cho-nai ) to which each float belongs, the floats should obtain permission from the coordinator (hariban) of the respective cho-nai, in the Oyamabayashi festival area (Fig.1,2).
Furthermore, as each float is only allowed to pass through the same cho-nai once, mobility is required to avoid clashes (butsuke) with other floats in order to clear the checkpoints while reading the movements of the other floats. It is easy to predict that this mobility and maneuverability could be influenced by the distance between the front and rear wheel axles (shinbou). If the distance between the axles is short, the turning capability may be improved at the expense of straightness, and it seems possible to move flexibly at the ‘last minute’ in the festival.
その一方で，この距離を縮めることはマエダケに上下方向の力が掛かると比較的容易に山車がピッチング方向に傾くことになり後輪のみに力が掛かるような不安的な状況も想定される。この不安定性はマエダケと前輪のシンボウとの水平距離にも大きく支配されることは理解できる。言うまでもないが，この距離が長い場合は安定し，車輪が浮くことは少なくなるように思われるが旋回性は落ち，機動性に問題が出てくるような状況も想定される。
On the other hand, reducing the distance between the axles (shinbou) can also lead to an unstable situation, where the festival wagon can relatively easily tilt in the pitching direction when forces are applied to the front frame (mae-tage), so that forces are transmitted intensively to the rear wheels. It is easily understood that further instability also tends to be induced by the horizontal distance between the front frame and the front wheel axle. If the distance is long, the vehicle may be more stable and the wheels will be less likely to lift off the ground, but turnability will be reduced and maneuverability may become a problem.
また，“ぶっつけ”中も演奏を続ける囃子方への衝撃低減も重要な事項であると思われる。お囃子の演奏ができなくなった山車も負けとなると聞く。囃子方はヤマが設置される区画の前部の水屋内で演奏を行うことになるので，“ぶっつけ”により衝撃力が水屋にできるだけ伝わらないように配慮する必要がある。
It is also important to reduce the impact on the musicians (ohayashi ), who continue to perform during the clashes (butsuke). According to one of the rules of the festival, if the float can no longer facilitate the playing of the musical accompaniment, it is deemed to have lost the battle. Since the musicians perform in the mizuya in front of the area where the yama is located on the wagon, it is necessary to ensure that the impact force is transmitted to the mizuya as little as possible during clashes.
この衝撃力の伝達緩和にはいくつかの構造戦略が考えられるが，一つはマエタゲから前輪シンボウ付近までの前部構造での局所的な衝撃力吸収かマエタゲーヨコタゲーウシロタゲによって構成されるフレームと車軸が取り付けられる左右のタテドダイ，そのタテドダイをつなぐヨコドダイで構成されるシャーシの全体で衝撃力を分散する方法などが，構造力学および振動工学的の観点から考えることができる。
Several structural strategies can be considered for mitigating the transmission of these impact forces. One of these is local impact force absorption in the front structure from the front frame (mae-tage) to the front wheel axle (shinbou) area. Another is a method of dispersing the impact forces throughout the entire chassis, consisting of the front frame, both side frames (yoko-tage ), the rear frame (ushiro-tage), the left and right longitudinal base frames (tate-dodai ) to which the axle is attached and the front and rear transverse base frames (yoko-dodai ) connecting the longitudinal base frames. The entire chasis may be designed from the perspective of structural dynamics and vibration engineering.
横町ヤマ（昭和３７年建造）側面図
by Professor Hidehiko Tsubogo, by Ymaguchi Univ.
横町ヤマ（昭和３７年建造）断面図
by Professor Hidehiko Tsubogo, by Ymaguchi Univ.
祭りのクライマックスである「ヤマぶつけ」を中心に考えると，対抗するヤマ同志が力を掛け合うポイントは，上図側面図のマエタゲ（前担木）である。そのため，「ぶつけ」における強さの要素として，マエタゲと車軸との距離は重要であることは容易に理解できる。
When considering the climax of the festival (the Yama-butsuke), one of the important structural elements which strongly affects the outcome when the opposing yama compete with each other is at the front frame (mae-tage). It is therefore easy to understand that the distance between the front frame and the front axle is important as an element of strength in the bumping.
この距離によって「ぶつけ」のときの衝撃，操作性は異なってくる。この衝撃に対する安定性，力の効果的な流し方を考えるとき，マエタゲに接続する側面のヨコタゲとシンボウ（車軸）との位置関係も重要になる。この間の距離を適切に取ることで下部構造の斜材が生きてくる。ここでは，代表的なヤマの寸法測定結果の一例を示す。
Depending on this distance, the impact and the maneuverability at the time of the collision will differ. When considering the stability against the impact and the effective flow of the impact forces, the vertical distance between the side frames and the axle* is also important. The braces of the understructure of the wagon seem to work effectively under the appropriate distance. Here are some examples of the dimensional measurements of the wagons.
ヤマの寸法調査表より by Professor Hidehiko Tsubogo, by Ymaguchi Univ.
the dimensional measurements of the wagons
この表から寸法項目として，a. 車軸幅，b. 前輪軸芯－マエタゲ，c. 全幅，d. 全長，e. 軸芯ーヨコタゲの６項目で，寸法データが完全に取得されている12機の山車に対して主成分分析を行い，ヤマ構造の分類を試みた。
A principal component analysis was carried out on the 12 wagons whose dimensional data had been accurately recorded. Specifically, the following six dimensional items were analyzed: a. the axle width, b. the distance between the front wheel axle and front frame, c. the total width, d. the total length, e. the distance between the axles and the side frame, and the distance between the wagon’s centre of gravity and side frame* in order to classify the structure of the wagons.
本町のヤマは他のヤマと比較するとかなり縦長なものとなっており，この分析においても特徴的に位置づけとなっている。この本町のヤマと対極に“ぶっつけ”において最強とされる横町のヤマが配置されることは興味深い。
The Honmachi-dori float is considerably longer than the other floats and is also characteristically positioned in the principal component analysis. It is interesting to note that the Yokomachi float, which is considered to be the strongest in the bumping, is positioned opposite the Honmachi-dori one.
この散布図の横軸と縦軸の意味を確認するために表：主成分得点係数の第１主成分の値を確認すると，右側ほど全幅の影響が強く，左側ほど前輪からマエタゲまでの距離が増え，これに合わせて全長が増える傾向にあることが読み取られる。
In checking the meaning of the horizontal and vertical axes of this scatter diagram, it can be seen that the floats positioned on the right side are more strongly influenced by the overall width according to the principal component scoring coefficients in Table 1, while the horizontal distance from the front axis to the front frame tends to be longer in the floats positioned on the left side, and the overall length tends to increase as well.
この傾向を確認するために前輪からマエタゲまでの距離と全長をそれぞれのヤマの全幅で割ったもので確認してみる（下表）。
This geometrical tendency is confirmed by the distance from the front wheel axis to the front frame and the overall length divided respectively by the overall width of each float (table 1 below).
The results show that the Honmachi-dori float, which has a large aspect ratio, is markedly longitudinal. Although there are no notable differences in the aspect ratios of the other floats, it can be read that the front structures of the Yokomachi and Seibu floats, i.e. the structure from the front frame to the front axle, seem to be more horizontally spread than the other floats. However, this structural characteristic has yet to be reconciled with the reasons why the Yokomachi float is considered the strongest. It may be one of the interesting tendencies of the float.同様に，第２主成分の値を確認すると，この縦軸の配置は下図に示す[車軸幅]と[車軸芯からヨコダケ上面までの距離]を掛けた面積の大小に対応していることがわかる。表中の数値は最大面積である駅前のヤマに対する比率で示してある。この面積比が大きいものほど主成分分析の縦軸上部に配置されていることが確認でき，ヤマ構造中心部の特徴の差異を明確に示していることがわかる。ここの面積を小さくすることで，機動性と強度を向上させることの可能性も否定はできない。
Similarly, checking the values of the second principal component shows that the arrangement of the floats along the vertical axis in the figure of the scatter diagram seems to correspond to the size of the area multiplied by the distance between the front axis and the rear one [a][𝑎] and the distance from the axis centre to the top of the side frame [e][𝑒] shown in the figure below.
The values a×e𝑎×𝑒 in the table in the figure below are expressed as a ratio of the maximum area of the float called EKIMAE (meaning ‘in front of the station’). It can be confirmed that the larger this area ratio is, the higher the area is placed on the upper part of the vertical axis of the principal component analysis, clearly indicating the differences in the characteristics of the mountain structure centre. I think that the possibility of improving mobility and strength by reducing the area here cannot be ruled out.
2. ヤマの構造 Structure of the yama
2.1. 横町のヤマと上新町のヤマとの構造比較 Structural comparison between the floats of Yokomachi and Kamishinmachi
ここでは，横町と上新町のヤマを比較してみよう。前節の寸法比較では，マエタゲから前輪軸芯までの距離が上新町のほうが横町より50cm程度長いだけで全体としては同様な寸法を示している。
Let us now make a structural comparison of the floats of Yokomachi and Kamishinmachi. The comparison of dimensions in the previous section shows that the distance from the front frame to the front wheel axle centre is only 50 cm longer in the Kamishinmachi float than in the Yokomachi float, but the overall dimensions are similar.
上新町の中央下部にスジカイを配置し，構造の強度向上を考慮した形跡が見られるが，横町の中央下部に周囲を囲むように水平に配置された板の方が効果的に構造強度をより上げているようにも見える。また，マエタゲに延びるスジカイが上新町のヤマの方が細長く，さらには水平からの角度も浅いように見える。浅い方がマエタゲからの水平方向の衝撃力を受けることに直接的であるが，細く長いことは，比較的に座屈が起きやすいことになり，横町と上新町を比較するとき，上新町のヤマの前部構造の方がやや弱く見える。
There are traces of consideration for the increased strength of the structure by placing the brace (coloured yellow) in the lower centre of the Kamishinmachi float, but the horizontally placed boards surrounding the lower centre of the Yokomachi float appear to be more effective in increasing the strength of the structure.
In addition, the brace extending into the front frame appears to be more elongated in the Kamishinmachi float and, moreover, the angle from the horizontal appears to be shallower. The shallower angle is more direct in receiving horizontal impact forces from the front frame, but the slender and longer construction means that buckling is more likely to occur, and when comparing the Yokomachi and Kamishinmachi floats, the front structure of the Kamishinmachi float seems to be slightly weaker.
2.2. 横町のヤマと本町通りのヤマとの構造比較 Structural comparison between the floats of Yokomachi and Honmachidori
アスペクト比最大のスリムな本町通りのヤマの中央下部の構造はスジカイや板のないフレーム構造となっている。前輪軸からマエタゲに延びる２本のスジカイが，ぶっつけのときのマエタゲにかかる衝撃を受け止めているように見える。その衝撃のほとんどはタテドダイに吸収されないと，このトラスでもなくラーメンでもない構造の中央下部では，強度不足となりそうである。後述するが，横町のヤマに見られるヤマ全体で衝撃を受けるようなことは期待できないとも読み取れる。衝撃力は前部に集中することになる。
The central lower part of the slim Honmachidori float, which has the largest aspect ratio, is a frame structure without braces or side-plates. The two braces extending from the front wheel axle to the front frame appear to take the force of any impact on the front frame. If most of the impact is not properly transmitted to the longitudinal base frames, the central lower part of this structure, which is neither a truss nor a rigid frame (rahmen), is likely to be insufficiently strong.
As will be discussed below, it is not expected to function structurally in such a way that the whole structure of the float, as seen in the Yokomachi design, could be subjected to the impact. With the structure of the Honmachidori float, the impact forces in the event of a bump are likely to be concentrated in the front part of the structure.
3. ヤマの変化 －横町ヤマに見る構造の変化 Changes in the float – the structural changes in the two floats of Yokomachi
ここまでは，丁内間のヤマの構造の差異を見てきたが，その中でも最強とされる横町のヤマの構造の変化見ていきたい。昭和37年建造のヤマと現在に続くヤマとの構造比較を行う。この比較においては，これまでの側面図からの考察と比較ではなく，図面から再現された３DCADモデルに対する物理シミュレーションを通して，このヤマ構造の変遷の意味を探ろうとした。
So far, we have looked at the differences in the structure of some floats built by different local area associations (chonai) and now we would like to look at the changes in the structure of two floats constructed in the Yokomachi local area. The Yokomachi float is considered to be the strongest of all the floats. A structural comparison has been made between the float built in 1962 and the other float that continues to be used to the present day. In this comparison, an attempt has been made to explore the engineering meaning of the changes in the structure of the float through physical simulation in a 3D CAD model reproduced from drawings, rather than merely through a simple consideration and comparison based on side views as in our previous investigations.
まず側面図からは，左側の平成元年調査のヤマと右側の平成21年調査のヤマとの間に見られる顕著な違いは，マエタゲと土台をつなぐ斜材（赤色）と中央部の横板（黄色）に見られる。
However, at first, from the lateral view, some striking differences between the float of the 1989 survey on the left and the float of the 2009 survey on the right can be seen in the braces (highlighted in red) connecting the front frame to the base frame and the central transverse plate (highlighted in yellow) set out in the figures below.
前者では斜材は左右に2本であり比較的短く細い。それに対して後者では長く太く左右に１本が配置されている。この違いは，前節の本町通りと横町のヤマの比較においても同様に見られるが，平成元年の横町のヤマはさらに華奢な構造に見える。中央部に関しては平成元年のものが横板と後方の斜材で構成されているのことに対して，高さのある横板一枚（右図黄色部）で側面が構成されているように見える。この部分は３D視点で見ると，この高さの板４枚で構成される四角形のフレームが配置されていることがわかる。
In the float of the 1989 survey, there are two braces (one on each side) which are relatively short and thin in the front part of the float. In contrast, the brace of the float of the 2009 survey is long and thick. A similar difference can also be seen in the comparison of the Honmachidori and Yokomachi floats in the previous section, but the float of Yokomachi in 1989 appears to have a slenderer structure. The central part of the 2009 float appears to be composed of a single high horizontal board (highlighted in yellow, right), whereas the central and rear parts in 1989 are composed of shorter horizontal beams and braces (highlighted in yellow, left).
この側面図から顕著に読み取れる２つのヤマの構造の違いは，右の平成21年調査ヤマの斜材や横板などの構造要素（構造部材）が，左の平成元年調査ヤマの構造要素と比較して，前後方向に長く，ヤマ構造全体を連続的にかつシンプルに構成してる様子が見られる。
The structural differences between the two float structures, which can be clearly seen from this side view, are that the structural elements (or structural members), such as braces and beams or plates, of the 2009 float tend to be longer in the front-back direction than those of the 1989 float, and the entire structure of the 2009 float is composed more continuously and simply.
3.1. ヤマの側面図と断面図で構成された3Dモデル 3D models according to side and cross-sectional views of the floats
ヤマの基本構造は，進行方向を前後方向とするとその構造の中央部を前後に通る長軸を含む鉛直方向に展開する平面を基準に左右対称となっている。その構造は，基本的にはシンプルなフレーム構造であり，トラス構造とラーメン構造に加えて，横板を配置した平板構造との組み合わせになっている。それぞれの構造を構成する構造要素は車軸，車輪以外は基本的に矩形断面の角材と平板のみなので，２方向の図面（左側面図と断面図）のみから３Ｄモデルを再現することができる。
The basic structure of the float is symmetrical with respect to a vertical plane that includes the long axis that passes backwards and forwards through the centre of the structure. The float structure is basically a simple frame structure, consisting of truss, rahmen structures and a flat plate structure, using transverse plates. The structural elements that make up each local structure are basically only rectangular cross sectional square timbers and flat plates, except for the axles and wheels, so the 3D model can be easily reproduced from drawings of left-hand side view and cross-sectional view.
まず，ドローイングツールやCADにおいて側面図をトレースし，断面図を参考にしながら，CADの押し出し機能を利用して構造要素ごとに厚みを付け，ソリッド化を行う。左右対称なので，ほとんどの要素は左右いずれかのパーツを作成し，CAD内での「複製」と，断面図を手掛かりにした「移動」により比較的容易にヤマの３D構造を構成することができる。
First, the side view is traced in a drawing tool or CAD and, using the cross-sectional view as a reference, the 2D drawing of each structural element is thickened and defined as a solid model using the extrusion function of the CAD. As the elements are symmetrical, most elements are created as either left or right parts and ‘duplicated’ and ‘moved’ according to the cross-sectional view to easily construct the 3D structure of the float.
左側面図 the left-hand side view
断面図 the cross-sectional view
トラスとラーメンで構成される部材は基本的に軸方向の引張力，圧縮力を受けるとともに，局所的な曲げに起因する力も受け止め全体に伝達する。
側面図と断面図の整合が取れるように３Dモデルを構築した。下図は平成元年に調査された横町の山車である。この３Dモデル化を通して各パーツの寸法の確認，各構造要素の配置の状態，要素間のつながり方などの構造の特徴を具体的に把握することができる。
特に確認し易くなる部位は，前後輪の間のシャーシ中間部のロの字状に閉じている部分である。与えられた側面図と断面図だけではこの部位の具体的な立体構成は把握しにくいが，３D化することにより，その構造の特徴が明確になる。
平成21年度調査の横町の山車についても同様に３Dモデルとし，自由な視点での構造確認を行うとともに，❝ぶつけ❞の衝突シミュレーションが実行できるようにモデルの調整を行った。
A 3D model was constructed in which consistency between the side view and the cross-sectional view was ensured. The figure below shows the float of Yokomachi, which was surveyed in 1989. Through this 3D modelling, it is possible to check the dimensions of each part, the state of arrangement of each structural element, and the way the elements are connected. In addition, other structural features can be grasped concretely.
Particularly, it is easy to identify the structure of the rectangular-shaped frame in the middle of the chassis between the front and rear wheels. The specific three-dimensional structure of this part is difficult to grasp from the given side view and cross-sectional view alone, but by making it 3D, the features of the structure become clearer.
The float of Yokomachi, surveyed in 2009, was similarly modelled to check the structure from a free viewpoint in a 3D-CAD system and the model was adjusted so that a ‘bumping’ collision simulation could be carried out as well as the float 1989.
3D-model of the YOKOMACHI float
3.2. ヤマCADモデルの衝突シミュレーション Crash simulation of the float CAD model
側面図と断面図から作成した平成元年調査横町の山車と平成21年調査横町の山車の３DモデルのSATデータ（３Dデータの中立ファイルの一つ）をSimWise4D（機構・構造シミュレーションアプリケーションの一つ）にインポートし，同じ条件での衝突シミュレーションを実施した。
SimWise4Dにインポートされたヤマ3Dモデルのフレームは，有限要素法に従って，形状情報に加えてそれぞれのフレームを構成する材料の特性（弾性率，ポアソン比など）も仮想的に与えられ，物理シミュレーション・モデルに変換される。ここで，有限要素法とは，簡単に説明すると，任意の形態の構造体を材料特性に代表される物理特性に関する情報をもった小要素（大きさが無限でなく有限であるということで有限要素と称する）に分割し，小要素ごとにその構造特性を数理モデル化し，その後に小要素間の位置関係に従い構造体全体の数理モデルを構築する手法である。
SAT data (one of the neutral files of 3D feature data) of the 3D models of the floats created according to the side and cross-sectional views, was imported into SimWise4D (one of the mechanical and structural simulation applications) and a dynamical simulation was carried out under a condition of collision.
The frames of the 3D model float imported into SimWise4D were converted into a physical simulation model according to the finite element method, where the properties of the materials (elastic modulus, Poisson’s ratio, etc.) comprising each frame are virtually given in addition to shape information.
The finite element method, briefly explained here, divides a structure of an arbitrary form into small elements (called finite elements because their size is finite rather than infinite) including information on physical properties represented by the material properties, and then mathematically models the structural properties of each small element, and finally constructs a mathematical model of the entire structure according to the positional relationships between the small elements.
3.3. ２つのヤマの構造特性の比較 Comparison of the structural properties of two floats
物理シミュレーションでは，ヤマが左から右に斜面を降り斜面に固定された円柱にぶつかる際のヤマを構成する要素を伝達する内力／応力（ミーゼス応力：軸応力とせん断応力による平均的な応力の大きさの尺度の一つ）の時間変化を見ている。直感的に分かるように，応力グラデーションにおいて赤色に近いほど応力が強く，青色に近いほど応力が低いことを示している。
下図では平成元年調査横町の山車と平成21年調査横町の山車それぞれのシミュレーションを実施し，衝突時の応力の分布状況の比較を行っている。この比較により，２つの山車の側面から観察できる特徴的な構造要素であるシャーシ中央前部からマエタギに延びる斜材が２本の場合と１本の場合で顕著に異なる衝突に伴う力の伝達の状況が以下のように読み取れる。
The physical simulation visualizes dynamic changes in the distribution of the internal forces/stresses (Mises stress: a measure of the average magnitude of stress due to axial and shear stress) transmitting through the elements comprising the float as it descends a slope from left to right and strikes a cylinder fixed to the slope. Intuitively, the closer to red in the stress gradient, the higher the stress, and the closer to blue, the lower the stress.
In the diagram below, the simulations have been carried out for each of the floats from the 1989 survey and the 2009 survey, both in Yokomachi, to compare the distribution of stress during the collision. This comparison reveals force transfers in the collisions which are markedly different in the case of two braces or one brace extending from the front centre of the chassis to the front frame which are the characteristic structural elements observed from the sides of the floats.
the 1989 survey
the 2009 survey
平成元年調査の山車ではマエタゲとそれに延びる斜材において顕著な応力の集中が見られる（赤色部）。さらに，赤色に続く黄色の部分もマエタゲから中央下部にも分布しており，お囃子が控える部分にも衝撃の強さがそのまま伝わっているようするが容易に想像できる。これに対して，平成21年度調査の山車では，平成元年調査の山車とは明確に異なり，応力の集中が見られず，山車の構造全体が青白く，同じ大きさの応力が均等に分布しているように見える。これは，衝突時の衝撃が前部に集中することなく構造全体に分散していることを示している。
In the float surveyed in 1989, a remarkable concentration of stress can be seen in the front frame and the braces extending from it (red-coloured part*). In addition, the yellow-coloured* part that follows the red part is also distributed from the front frame to the lower centre* along the longitudinal axis of the braces, and it is easy to imagine that the strength of an impact may be directly transmitted to the part in which the musicians are performing.
In contrast, the float surveyed in 2009 clearly differs from the 1989 float in that there is no concentration of stress. Stress of similar magnitude seems to be evenly distributed as the entire structure of the float tends to be pale colored, comparatively. This indicates that the impact at the time of the collision is not concentrated in the front part, but distributed over the entire structure in the 2009 float.
特に中央部への横板周りの応力は低く，お囃子への衝撃の少なさを示唆している。この❝ぶつけ❞において囃子が中断されないこともこの祭りのおける勝敗を決定するルールの一つであることから，中央部への衝撃の少なさは，もっとも山車の構造に求められる応力集中による局部の損傷による運航不能の回避と同様に，重要なポイントの一つである。
結論として，斜材の配置の違い，その斜材から伝えられる力をうける中央部の構造の違いが，山車全体の構造特性の違いに大きな影響を与えていることが確認でき，その特性の違いが，この祭りでの❝勝敗❞において有効に働くことが再確認できた。
The stresses around the horizontal plates to the centre are particularly low (in Fig.2). It suggests that there may be little impact on the musical accompaniment. Since one of the rules of the festival is that the music should not be interrupted during the ‘bumping’, the low impact on the central part must be one of the most important points of the float design, on the same level as avoiding the inability to operate the float due to local damage caused by stress concentration.
In conclusion, it could be confirmed that the differences in the arrangement of the braces and the structure of the central part, which receives the force transmitted from the braces, have a significant effect on the differences in the structural characteristics of the whole float, and that these differences in the characteristics work effectively in the ‘win or lose’ drama of the festival.
4. ヤマの形の必然性 Conclusion
角館の飾山囃子について行われた民俗学的調査から、町の大工たちが山車の形状を改良し、木材の在来工法と鉄工所の技術を用いたマイナーチェンジが継続的に行われていることが指摘されていた。本研究では、この「工夫」が構造学的に意味を持っているのか、また、専門家の知識によらないコミュニティ内での集合的な知恵である「工夫」が、合理的であるのか否かの検証を行った。具体的には、山車の構造をモデル化して衝突シミュレーションを行い、この「工夫」は山車の前担木部分に集中する衝撃力を構造全体に流し、シャーシや車軸が受ける衝撃を緩和すると同時に、山車中央部の水屋周辺への衝撃力伝達も回避することが確認できた。このことより、「祭りに勝つ」というモチベーションが山車構造の最適化につながる「歴史的な知恵の蓄積」という行為につながっていることの可能性も示唆された。
This study examined whether the aforementioned ingenuity has structural significance or not and whether that ingenuity, which is a collective wisdom within the community that does not rely on expert knowledge, is rational or not.
Specifically, the structures of the floats were modeled using CAD and collision simulations were performed. As a result, it was confirmed that the ingenious design dissipates the impact force concentrated on the front frame of the float throughout the entire structure, thereby reducing the impact on the chassis and axles while avoiding transmission of impact force to the mizuya area around the centre of the float. It suggests that this “historical accumulation of wisdom,” which is motivated by a desire to “win at the festival,” may lead to optimization of the float structures.
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