-------------------------------------------------- page 1 GUIDE to the use of Harrison's Patent Setting-out Instrument FOR CARPENTERS, JOINERS, MASONS, AND OTHERS. WITH PLATES ON HANDRAILING, ROOFING, AND SKEW ARCHES. By HARRISON BROTHERS, Steeple Grange, Wirksworth, Derbyshire. -------------------------------------------------- page 2 A Specimen of Handrail wreath worked in stone by the aid of this Instrument. Being one complete revolution in three parts. each part 1/3 of a circle between joints, the whole having four different pitches, the rail being 2 1/2" by 1 3/4" in section, each piece forming its own ramp and easing, and worked out of stone not more than 3" thick. -------------------------------------------------- page 3 WHILE introducing this method and instrument to the trade, we ask your attention while we explain its use. Knowing something of the difficulty experienced by ordinary minds in mastering any of the methods now in use, we are sanguine enough to believe that a method which enables any intelligent mechanic to construct work, which for accuracy equals the efforts of past masters in the art of handrailing, without devoting so much of his scant leisure to the study of abstract problems, will be readily appreciated. Let it be understood that the following rules be adhered to when using this instrument: The thickness of material required need never be more than the length of a line through a section of the rail, where such line will be longest. See Fig. 1 All lengths will be taken on centre line of rail, all joints will be radius lines when finished, and square from face of plank or material before working to twist. The plank or material may have either one or two pitches, but not more. The face mould for each piece of wreath is some part of an elliptic curve; for example, the diameter never alters one way, whatever the pitch. See Figs. 2 and 3. In cases where only one pitch of plank is required, that is to say, where one joint is plumb, as starting from a newel or level landing, the wreath will be raised on an imaginary pivot at right angles to the joint. Where two pitches are required, as where the shank or bottom joint stands on the pitch, the wreath will be raised on the chord line, thus throwing the bottom joint or shank to a given amount of pitch, which may be varied by applying more or less of the twist to the top joint. The angle of twist given by the instrument will always be the amount required for a quarter circle. If position of joints are more or less than quarter circle, add or subtract as required from angle of twist given. If two pitches are required, add half the result to the reading for quarter circle, or less, as the chord line on plan makes a greater or less angle than 45°. See diagram A. The amount of twist determines width of face mould at each end. All the twist applied at one end of wreath gives only one pitch, when one tangent will remain same length as on plan, and one joint plumb. Half the twist applied to each end gives two equal pitches, when both tangents to elliptical curve must be same length. The mechanic should understand that the length of tangents rule the twist and vice versa, the relation being between the top joint and bottom tangent, and the opposite. -------------------------------------------------- page 4 EXAMPLE No. 1. It is required to make a piece of wreath to a quarter circle, starting from a newel or a level rail. First strike the centre line of rail to quarter circle on drawing board, full size, draw a line from joint to joint on plan, which will be called chord on plan. Enclose the portion of circle by tangents, which are always lines at right angles to one radiating to any given point from the centre. Now set arm marked chord on plan across the instrument so that the length shall correspond with line on drawing, viz., chord on plan, and the figures read the same on either side of the square slot, and arm marked height square from it, and fasten by screw. Then set arm marked chord on pitch so far up the one marked height, as one joint is required to be above the other, or in other words to the pitch, and so that the figures at the other end of the arm cut at exactly the same place on the slot as the first one. The reading there will be length of chord on pitch, at the same time the reading on the quadrant will be the amount of twist required. As this piece of wreath has only one pitch, the tangents of face mould remain the same angle as the plan, viz., at right angles, and only one of them, the top, increases in length. Loose the screw and remove both arms, then take striking rod and set marking point to O, and first stud to radius of circle on plan, which never alters, slide into horizontal slot, make horizontal line on the wood or zinc intended for face mould, this line will be long diameter of elliptic curve; from the end of this line square up one to the length of bottom tangent, from this square out the top tangent indefinitely, and where the length of chord on pitch cuts this is its length. Lay the instrument on material intended for mould parallel with the horizontal line, and so that the striking point cuts through the length; of chord on pitch while the first stud is travelling in horizontal slot, the other stud is fastened to striking bar in such a position as will enable the point to pass through the other end of line of chord on pitch while the stud is travelling in the vertical slot, when the correct sweep of the face : can be struck. Next the joints of face mould, as one joint is required plumb, one tangent will be same length as plan; and as all joint lines of face mould are square from tangent lines on its surface, it will be easily grasped by the student when applying the rules that have been already given. The bottom tangent is squared out from base line to same length as tangent on -------------------------------------------------- page 5 plan. The top tangent cutting from there to the length of chord on pitch is the line to square from for top joint. In this case the joints of face mould are at right angles to each other, same as the plan. EXAMPLE No. 2. Required a piece of wreath to a quarter circle having two equal pitches. Notice, in Example No. 1, the wreath having only one pitch, the plank is raised on the joint line to make the construction simple, as it causes the joints of face mould to be same as the joint lines on plan, square from each other. The major axis, or long diameter of curve, to be in line with the bottom joint. But this having two pitches must be raised on the chord line on plan, then the length of chord on pitch given by the instrument will be parallel to long diameter of elliptic curve. The reading on the quadrant must have half added; viz., if the reading shows 30° add 15°, total 45°. To strike the face mould, draw line to same length as reading on arm, marked length of chord on pitch. Lay instrument on parallel to line on which it is raised, square up from half its length, and mark equal to on plan which will be short diameter of curve. Fix studs in striking rod to cut these three given points. For joints of face mould, both pitches being equal, square up from centre same as plan, lines cutting from this to length of chord on pitch will be tangents to face mould, and square from these the joints. Both pitches being equal, half the twist is applied on each end. The same example, but having unequal pitches. The plan, height, and pitch being the same, the instrument gives the same result, viz., length of chord on pitch and amount of twist. The student must first determine what difference in the pitches is required in the following manner. Mark the given pitch of straight rail or shank, as shown in Fig. 5, then two parallel and horizontal lines the same distance apart as the radius of circle on plan, continue the pitch of shank to cut these, when the length of this between the lines will be length of bottom tangent; and from end of this line to the other end of chord on pitch, see Fig. 5, is the length of top tangent; and the difference in these two tangents is the difference of twist between top and bottom ends. To obtain this difference, draw lines equal to the length of each tangent, and parallel to each other, as in Fig. 4. Then divide the greater increase by the lesser, and divide the angle of twist in the same proportion. See Fig. 3. -------------------------------------------------- page 6 For example, if the lesser increase is contained in the greater three times, the result will be as three to one, or 3/4 of the twist in the greater and 1/4 in the lesser. EXAMPLE No. 3. Required a piece of wreath for a portion of a circle being less than quarter. First strike portion of circle out full size on drawing board, and continue same to quarter circle, mark position of joints on plan, join joints by chord line, and enclose portion of circle by tangents. Proceed in same manner as No. 2 to make arm marked chord on plan, equal line called the same. Set up other arm to height and read off length of chord on pitch, also angle of twist, which must be divided as under. Divide quarter circle on plan into any number of equal parts with compasses, so that the joint line shall just correspond with any number of such equal parts. Then divide given amount of twist into same number of parts as quarter circle, and subtract same number of parts from twist as joint takes from quarter circle. Now add proportion of twist according to diagram marked A. Always remember that for quarter circle add half of amount; Ditto, eighth of circle add quarter of amount; Ditto, sixteenth of circle add eighth of amount, and per ratio. Quarter circle is the maximum; any difference tends towards zero, whether greater or less than quarter circle. Note this for Example No. 4. If wreath is to have equal pitches, half the amount of twist will be applied at each end, and both tangents to face mould will be same length. If unequal, find pitch of either tangent by method described on Fig. 5, when remainder will be the other tangent. Divide twist according to difference of tangents, as Fig. 4. EXAMPLE No. 4. Required a piece of wreath greater than quarter circle. Proceed in same manner as in Example No. 3, only add instead of subtract to the amount of twist given, according as the joints exceed quarter circle, which will never be much in practice. As the method is the same whatever the size of curves or amount of pitch, or position of joints on plan, no useful purpose will be served by multiplying the examples. -------------------------------------------------- page 7 The Authors are satisfied that, by thoroughly mastering Example No. 2, the student will be in a position to intelligently work out any problem in handrailing that may be required of him, or, in fact, any similar work. For it will be noticed that any piece of circular ramped stone coping is simply a piece of work in every respect the same as a handrail wreath, being more or less complicated, according to whether it has one or two pitches. That is to say, whether one or both joints are square from the pitch when finished, for the joints are always made square from the face of material before the twist is worked on. Skew Arches. The instrument is of great service to Masons and others who have to get out the shape of voussoirs for the above. First set the arm marked (chord on plan) to the diameter of arch, if a semi, to any convenient scale, and fasten with screw. Then set the other arm to same scale up the one marked height to the amount of skew, when the major axis of elliptical curve for skew centre and face moulds may be read off by making the arm cut the other at exactly the same place in the slot as the one first set, and reading the result to same scale. The angle of twist shown will be the proper amount required between crown of arch and springing, so that if it is divided into the same number of parts as there are intended to be stones in the face of arch between crown and springing, the bed moulds may be made to these, also the same angle applied to the joints to make them parallel on the soffit, starting with the centre of keystone square from face of arch. Stones should be first dressed true on face, and one edge square from it. If the arch is a segment, subtract from degrees of twist as much as it is less than quarter circle between springing and crown. NOTE - Always remember the keystone contains only half amount of twist applied one way, and half the other. Although the plate shows the arch to be a semi, a segmental one is stronger when constructed on the Helicoidal method. Hip and Valley Roofing. The lengths of Hip and Valley rafters, and the cuts for top and bottom of same, may be readily obtained by setting the arm marked (chord on plan) to same length as seat of rafter, and other arm to height, when the length of rafter may be read, also bevel for top and bottom of same. --------------------------------------------------- page 8 When seat of Hip Rafters are square, half width of building on each slot will be seat of rafter. Cross bevel or mitre for top of Hip or Valley rafter, obtain from down bevel, see Fig. 9. Notice down bevel of Jack rafters is same as that for common rafters, and cross bevel of Jack rafters obtain in same manner as Hip. NOTE - Whatever scale is used for lengths, degrees of bevel read in full. Also whatever the reading is for top bevel, the bottom one will be the remainder of 90°, viz., if top bevel is 60° bottom bevel will be 30° The difference in length of Jack rafters obtain by marking cross bevel of Jacks and spacing two rafters on it. See Fig. 6. For backing of Hip rafters, apply the top bevel of common rafters across the mitre from longest point with stock down the plumb cut, or the square applied on the same will give the other side. See Fig. 7. Either 1 1/2" or 3/4" scale is most convenient, according to whether the job is large or small. In taking the sizes, first obtain width of building and rise of roof; for example, if building is 20 feet outside to outside of wall-plates, and roof rises 7 feet, set the instrument to half width of building on arm marked chord on plan, and 7 feet in height, and the reading will be 12' 2" for common rafter, with 35° bottom bevel, and 55° top bevel. Again, set instrument to half width of building on each slot, with arm marked chord on plan to cut these, and the 7 feet rise up the one marked height, when the reading on the arm marked chord on pitch will be 16 feet where it cuts half width of building on the slot same as the other arm. This is the length of hip rafter, and the reading on the quadrant gives 26° for bottom cut, and the remainder of 90°, viz., 64°, will be top cut. Take a board, and mark the lengths and bevels on, as Fig. 9. To obtain the mitre for the ends of Purlins, mark position of same on common rafter and drop perpendiculars from the two upper surfaces (see Fig. 8), then the distance apart of these on the horizontal line will be the amount that the cut requires to be under square on each surface. This method is also useful for cutting the mitre of a cornice or anything standing on the rake. If the plan is greater or less than a right angle, apply the mitre of ground plan across two parallel lines the same distance apart as the perpendiculars from each surface. --------------------------------------------------- page 9 -------------------------------------------------- page 10 -------------------------------------------------- page 11 -------------------------------------------------- page 12 --------------------------------------------------- page 13 --------------------------------------------------

Emails

----Anyone with more details for publication on this webpage, please email ---- Michael Nelson writes on 27jan2012: Dear Mr. Palmer I am very interested in Harrison Brothers and particularly the source of these photographs. The item shown and described as a “pot” is actually a tobacco jar. My mother has an identical one made by Isaac Harrison (her Father) but so far as I am aware it is not the one in the photograph. We were unaware of another example. Completely unknown to all of us is “Harrison’s Patent Setting-out Instrument”. Does an example still exist? Any information would be greatly appreciated. Kind regards. Michael Nelson

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