Involute spline vs straight spline shaft

Involute spline vs straight spline shaft. External Broaches: These are used for cutting splines on the external surface of a component, such as on a shaft. We work closely with our customers to ensure they get tailored spline shafts that meet even the most complex and unusual specifications. This is one of the many methods Strength of a Splined Connection. It is because the splines of the gear are processed into the length of Mar 1, 2004 · This involute, or “side fit” profile is the most common used spline in production today. Spline gauges can be manufactured from 5mm up to 500mm. The tooth. The first three standards are outdated and superseded by [9]. Spline gage profiles include involute, serration, and parallel (straight or helical). Although these components are rather expensive, subject to direct wear, and difficult to replace, transmissions with gears and splines are required for two very simple reasons: 1) Motors have an unfavorable (disadvantageous) relation of Spline shafts are widely used in the agricultural industry, trucking industry and where large torque requirements is a must. Nov 8, 2021 · Involute Splines. Spline shaft A 35 x 31 x 18T. It is emphasised that the splines identified are side fit with the centering based on the sides of the splines. Push Broaches vs. /2 § R = Radius to any point on the involute curve § S alpha = arc length from start of the involute to the tangent point § S R = tangent line length at any point X,Y on the involute § S Ro = tangent line length at major diameter Mar 20, 2015 · The serrated area on the end of the shaft is called the spline. Ball Screw/Splines and Bearings. There are three major pressure angles used in the spline rolling industry today. Full form go ring gages for checking major diameters, minor diameters, and tooth thickness. Tolerance and Fit: Ensure that the spline shaft’s tolerances match the mating component. Load distributions of the example spline under pure torsion loading at different torque levels. September 1, 1990. while not crucial, this is going to play a part in wear characteristics, especially when mating it with parts that already have a true involute Jan 8, 2009 · 9163 posts · Joined 2000. 10. Parallel splines have large, straight-sided teeth that resemble machine keys and transmit more torque than involute spline Dec 16, 2017 · If you have to model the involute spline shaft, you will be tempted to use the Derive function in Inventor to determine the female bore. See the figure below. A complete Mar 6, 2021 · Involute splines can be produced by gear manufacturing techniques and have the ability to self-centre under load. They are made in single or multiple thread designs, with diametral pitches ranged from 2. Involute Splines. Involute Spline Hobs have straight sides teeth like a gear hob, and are usually of stub tooth depth. fit splined couplings, mainly, the restrictions associated with the Involute splines can shall produced by outfit custom techniques and have the skilled to self-centre under recharge. Straight Sided Spline Dimensions. If you're talking about an automotive involute spline, they almost always use a stub form, typically 12/24 DP, or 16/32DP. BS 2059 Straight-sided splines and serrations WebDesign Guide for Involute Splines Robert W. Involute Spline and Serration Design Calculator for the following engineering standards: ANSI B92. 50″ to 48″. Splines with involute flanks have a very high line of contact inthe nonworn condition, This reduces increase ofclearance due to wear within the l!ifetimeof the spline, compared to straight-sided splines. The Society of Automotive Engineers (SAE) has published the ANSI B92. For the calculation, the number of splines millrmetres, of straight-sided splines for cylindrical shafts with internal centering, light series and medium series. They can be external or internal. D = major diameter of splines (mm) d = minor diameter of splines (mm) l = length of hub (mm) n = number of splines. See the figure Straight Spline Calculation. T = 4,000 Nm under pure torsion load-ing. Precise Alignment. Straight cylindrical involute splines manufactured in accordance with ISO 4156 (all parts) are used for clearance, sliding and interference connections of shafts and hubs. In this calculation, a splined connection with a length L, height H and width b at a shaft with a diameter D is considered. 1 standard. ANSIB92. Enter the spline dimensions. Pull Broaches. Works OK, but I'm worried that the torque on it might just eventually shear the key off. There are certain manufacturing challenges when dealing with major dia. 050” tooth height cannot typically be done due to the tooth height. Through many years of experience, we have the knowledge and expertise to produce both external and internal spline gears to fit almost any application. 3804" (other measurement was mm) radius. 2 Dimensions The nominal dimensions common to shaft and hub, d, D and B are given in table 1. Splines: Module-DIN 5482 Involute Spline ENGINEERING OF INVOLUTE SPLINES. ” Splines are designed and made with an involute form, due to the ease of manufacture and its self-centering attribute. As one of the top manufacturers of spline shafts, Circle Gear provides a wide range of configurations for our custom spline shafts. 5 and 45o and can include between 60 and 100 splines per the American National Standard. Limiting dimensions, tolerances, manufacturing deviations and their effects on the fit These broaches generate the splines by the top of the tooth & by cutting splines to finish hole in the component. Parallel Key Spline. Gear Solutions—Inside splines . Jul 12, 2023 · Types of Splines. Involute splines are made with pressure angles 30 o, 37. 1-1970, ANSI B92. Splines are in fact a series of keys machined on outside of a shaft, with corresponding grooves machined on inside of hub of a power-transmitting element (such as gear, sheave, sprocket, pulley etc. Engineering design requires many different types of gears and splines. Parallel-side spline's have been standardized by the SAE for 4, 6, 10, and 16 spline fittings. It describes the types of splines that are typically used - including flexible and fixed splines. upon a 30-deg pressure angle in order to give a wide- base tooth for strength and yet be of a nature that will slide along its length under normal torque loads. 4). 2} To insure fun surface contact on the tooth flanks, independent of the The American standard for involute and straight-sided spline profile ANSI B92. The externally splined shaft mates with an internal spline that slots, or spaces, formed in the reverse of the shaft’s teeth. Involute splined are made by pressure angles 30 zero, 37. , by the standards [3–5]and[6]. There are two basics types of splines: the flexible spline (working) and the fixed splined (nonworking). Notes: Number of Teeth: Between 6 and 50) Dec 31, 2020 · Step 2: Involute in gears and splines In splines or spur gears, a fraction of the profiles is an involute of a circle. : DIN 5481 Serration – 55° Included; DIN 5481 60° Inc. 2) A flexible piece of wood, hard rubber, or metal used in drawing curves. The interlocking splines provide a larger contact surface area, ensuring efficient power transfer. Figure 4. The curves increase strength by decreasing stress concentrations. That is, a gear's profile does not depend on the gear it mates with. In the JIS standard a pressure angle of 20° is also proposed. SAE Parallel Side Splines Table of Sizes and Dimensions. As a result of calculations, shear stress τ and crushing stress σcr in the splines are determined. 1; IS 2610 – power transmission-straight sided splines available machine equipment dimensions. The calculated grinding wheel form accommodate sided spline [6]. It lays down the following fundamental principles: On the ribbon, click Design tab Power Transmission panel Involute Splines. The benefits of using a splined shaft in ISO 14-- Straight-side splines fir cylindrical shafts with internal centering . 5 and 45 o and can incorporate between 60 and 100 splines per the U National Standard. A straight spline of 25 - 6x21x25 is selected. It establishes a specification based on the metric module within the range 0. Pack it *ALL* out you pick up after your dog, so clean up after YOU, too. Splines are a long discussion with many folks: number of teeth, pressure angle, length of engagement, involute versus straight-cut profile, and so on. The DIN 5480 involute spline standard would be the best for you to use, see image attached. Jan 1, 2005 · The externally splined shaft mates with an internal spline that has slots, or spaces, formed in the reverse of the shaft’s teeth. 5 and 45 o and cans contains between 60 also 100 splines on the American National Standard. 5 module to 12 module. 2M. Involute splines are made with pressure angles 30o, 37. 5 deg, and 45 deg. Just as an example of what is available, take a Contents. The SAE Standard for involute splines is based. This Spline Design Data is based on ISO 5480. AmTech’s shafting manufacturing capabilities include the production of spline shafts for axles, power transmission, gearboxes and other Sep 1, 1990 · Involute Splines. The shaft is under the action of torque T . Involute Spline Design Guide : Colleen Hoovers "It Ends with Us" This touching tale of love, loss, and resilience has captivated readers with its raw and emotional exploration of domestic abuse. WNXE generates a true-scale drawing of the involute profile of both, internal and external involute spline. 5°, or 45°. 5° and 45°. SKU: S82T18D3531 Category: Spline shafts. This International Standard also specifies control methods and corresponding gauges. The 30-deg pressure angle is also advantageous on. Ask a question. Spur Gears. (2) Step 3: Internal and external splines. Manufacturers design these components to mesh precisely with a mated part. Push Broaches: These are pushed through the workpiece from one end to the Mar 6, 2021 · Involute splines can be produced by gear industry techniques and have an feature to self-centre on load. 1, a common alternative to this is the involute splines, but these are not covered in the present paper. ISO 5480 standard applies to splined connections with involute splines based on reference diameters for connecting hubs and shafts either with a removable connection, a sliding fit or a permanent fit. Splines provide a connection between two shafts or other components that transmit torque and rotation. Each control vertex you add increases the curve's degree. The numerator defines the diametral pitch, and the denominator is the stub pitch. Grinding of fluted shafts, splines and involute splines per DIN and SAE standards as well as individual shapes. From one compact system, transmit linear or rotary motion or both at once (sometimes called spiral motion). Design Guide for Involute Splines Robert W. e. N = Number of splines. Broached Sleeves & Flanged Bushings. 500″ Go and No Go spline gauges that confirm to ISO, DIN, AGMA, and JIS standards. THE SAE standard for involute splines, which has also been approved by several other societies, has been nine years in the making. 0 M t = p m · A · R m. The involute gear profile, sometimes credited to Leonhard Euler, [1] was a fundamental advance in machine design, since unlike with other gear systems, the tooth profile of an involute gear depends only on the number of teeth on the gear, pressure angle, and pitch. Serrations More exacting requirements on torque transmitting splines compelled designers to look for ways to satisfy the following conditions: 1) To increase the contact surface without decreasing the minor diameter of the shaft or increasing the major diameter of the splined hole. Applications of Spline Broaching. 5° and 45° pressure angle, parallel straight sided splines and modifications to spline geometry such as lead modification, missing tooth, and end geometry from the manufacturing process. External in the shaft and internal in the hub. , parallel) splines, involutes splines offer several advantages, including: Simpler design, which allows for easier—and thereby cheaper—manufacturin g operations Greater contact area along the tooth profile, resulting in smoother operation Higher tolerance for misalignment Jul 29, 2009 · A common spline has straight sides -- there are no involute curves involved. Involute splines have teeth similar to gear teeth except spline teeth are Apr 7, 2020 · Although involute splines of 30° pressure angle are very popular, this information sheet also covers involute splines of 37. Grob’s cold formed spline shafts are made with an even number of teeth and are parallel over two or more teeth. Involute splines are almost always 30° pressure angle. : DIN 5481 Serration – 60° Included; DIN 5482 Inv. Involute splines can be seen as a gear with special profile in line with international and national regulations. Metric module, side fit. The profile of a straight sided spline is defined by. Hoover expertly weaves a story of hope and healing, reminding us that even in the darkest of times, the human spirit can succeed. #2 · Jan 8, 2009. 15-1960, SAE STANDARD - 1950, SAE J500, NAS 541/2, 580/1, DS360/361 The tables below show the dimensions of a straight sided spline in accordance with BS 5686:1986, ISO 14-1982: Specification for straight-sided splines for cylindrical shafts: metric nominal dimensions, tolerances and gauging requirements. So I'm trying to figure out the angle on the involute splines in the gear. 5 additionally 45 zero and can include between 60 furthermore 100 splines per the American National Standards. Resources . 1 Introduction. Randii. Jul 19, 2017 · July 19, 2017. BE CAREFUL, with this method, the internal bore will be exact size, metal to metal contact. For computer programming, the Oct 11, 2019 · A free body charts analysis of a straight-sided spline system would show to physics is the same — an applied radial load willingness must supported by a centering energy, resulting in unequal tooth cargo sharing, as includes an involute spline. They’re also better than keyed shafts for applications requiring frequent disassembly or adjustments because you can move bushings along their splines. Involute spline. Timing Pulleys. 25″ to 18″, and a length of 0. IS 3665 – Dimensions for involute-sided splines. It was cut to sit on a 1"OD rod. If the spline is designed for an after-market product (for example, a sprocket or a spline shaft), then a you are just getting straight sides on the spline. This standard provides data and guidance for the design, manufacture, and inspection of straight, non-helical, cylindrical involute splines. 1-1996, ASA B5. Straight cylindrical involute splines — Metric module, side fit — Part 1: Generalities 1 Scope This document provides the data and indications necessary for the design and manufacture of straight (non-helical) side-fitting cylindrical involute splines. The torque transmitting capacity of splines is given by, Eq. These splines are known as straight splines. Involute splines are produced with pressure elbow 30 o, 37. Major diameter fit spline is suitable for applications where axes alignment between two parts (internal and external spline) is a critical design parameter. 1. Splines may be straight sided, tapered, or have an involute form. Spline and serration forms are described by an involute profile geometry with crest flat, root flat, pressure angle, and radius transitions at a fixed chordal pitch. D i: The reduced diameter = 21mm, r: the mean readius of the teeth = (21+25)/4 = 11,5mm c: The chamfer radius on the teeth (top and bottom) is assumed to be about c = 0 This WebDesign Guide for Involute Splines Robert W. It allows the shaft to be installed and removed for service. Aug 21, 2023 · Splined shafts are designed to transmit higher torques compared to plain shafts. 5 and 45 degrees. The 30 degree pressure angle is most often used when the two members 30° involute splined shafts. Serrated – have teeth that are in the form of a ‘V’. For these reasons the spline with in-volute flanks is the most frequently used connection. Straight-Sided Splines - Compared to straight-sided (i. Splines are the ridges or teeth (external spline) on a drive shaft that mesh with an equal number of like ridges or teeth Oct 29, 2023 · Internal Broaches: These are designed for cutting splines on the inside of a component, such as within a bore or hole. Standard Code: Spline Detail (D) Shaft Diameter (SL) Shaft Length (TL) Total Length: SAE AA: 9T 20/40 DP: 0. Involute. You can either create new shaft groove or select existing groove. IS 3665 – Dimensions for involute-sided splines; IS 2327 – Straight-sided splines for parallel shafts; BS 2059 Straight-sided worm and teeth A spline is a ridge or tooth [1] [2] [3] on a drive shaft that matches with a groove in a mating piece and transfers torque to it, maintaining the angular correspondence between them. eg. 8 in stock. Involute splines can subsist either Select fit with Round fit Figure 6 shows load distributions of a spline having a misalignment of φ = 0. Involute splines are the predominant form bacause they Splines having straight-sided teeth have been used in many applications (see SAE Parallel Side Splines for Soft Broached Holes in Fittings); however, the use of splines with teeth of involute profile has steadily increased since 1) involute spline couplings have greater torque-transmitting capacity than any other type; 2) they can be produced A specific type of spline known as an “involute spline” shaft enables a manufacturer to facilitate this type of mechanical assembly; it relies upon inwardly curving equally spaced grooves in the spline that do not display straight-sidedness or any sharp corners. 003 in for shafts 31⁄2 to 6 in, inclusive, for 4-, 6-, and 10-spline May 17, 2014 · I got a gear with 6 internal splines. side fit splines. (See Fig. They contain all the necessary characteristics for the assembly, transmission of torque, and economic production. Deriving the Involute Curve Equations -- Terms Cylindrical Coordinates § R i = Base dia. Involute splines offer smooth power transmission and are commonly used in high-torque applications. I couldn't find a cheap splint shaft so I just put a keyed 7/8" shaft inside with a key. The rotation of the splined shaft is transferred to the internally splined member, such as a gear or other rotary device. Shaft Length: Max 140”. Further, the involute splines guarantee self-centering action of hub and shaft which are being under load. A spline is a set of narrow generated longitudinally around the circumference of a shaft or grooves generated on the inside bore of a workpiece. For instance, a gear mounted on a shaft might use a male spline on the shaft that matches the female spline on the gear. Also, the ever changing spline specifications Involute splines can be produced by gear manufacturing techniques and have the ability to self-centre under load. On the Design tab: Click the arrow next to the Splines Type edit field to select the spline. This paper gives data and methods to supplement the standard, including intermediate tables for experimental enginering and a few new convenient formulas. These angles are 30, 37. Sep 20, 2016 · Crowned – are usually involute splines whose teeth are crowned or curved to compensate for angular misalignment. Specify the position of a shaft groove. a spline for a 50mm OD spline with say a module of 2mm would have a PCD (D) of 50 - 2 = 48mm. Mar 6, 2021 · The American standard for involute and straight-sided spline profile ANSI B92. Add to cart. The sides of the equally spaced grooves are parallel in both directions, radial and axial. Cedoz,Michael R. /2 § R o = Major dia. Thus, straight-sided splines should provide centering similar in magnitude to an involute spline that has a Parallel splines have large, straight-sided teeth that resemble machine keys and transmit more torque than involute spline teeth. The DIN 5480 series of standards is limited to splines with a pressure angle of 30°, since pressure angles of 37,5° and 45° are covered by ISO 4156. Jun 15, 2022 · 9. ) The tooth flanks can optionally be The following are equations and engineering design calculator to determine critical design dimensions and features for an involute gear. Cedoz 1994-01-01 The purpose of this design guide is to provide the designer help in understanding the design, manufacture, and operation of splined shaft connections. Because of these different motions, these ball screw/splines and bearings create efficient, fluid movements in complex automated applications, such as pick-and-place robots. Engineer's Edge—Spline engineering design formula Nov 15, 2018 · Although involute splines of 30° pressure angle are very popular, this information sheet also covers involute splines of 37. WNXE software calculates dimensions and profile of external spline (shaft) and internal spline (hub). 12° along with different lead crown modifi-. Where: M t = transmitted torque (N-mm) p m = permissible pressure on spline (N/mm 2) A = total area of splines (mm 2) R m = mean radius of Aug 20, 2020 · Although involute splines of 30° pressure angle are very popular, this information sheet also covers involute splines of 37. Involute splines have curved teeth, similar to the teeth on a gear. You can sketch a style spline as a bridge curve between two existing entities. - VIRTUAL RALLY for the HAMMER TRAILS in JOHNSON VALLEY Post 1349. Hence, straight-sided splines should make focusing similar in magnitudes to an involute spline that Compared to keyed shafts, they last longer and handle higher torque. We manufacture durable straight spline broaches used to form splines with teeth of straight or angular lines. Grob Standard Spline Shafting has been designed to maximize torsional strength and contact area. When your project requires mating parts, look no further. Splines: Module-DIN 5480 Flat Root Involute Splines; DIN 5481 55° Inc. Apr 29, 2021 · The splined shaft works as a linear guide when coupled with a bearing with an internal spline gear mechanism. You're not looking for convoluted splines You're looking for involute splines. While straight-toothed splines can accommodate only small misalignments of less than 1 degree, crowned splines can handle misalignments of up to 5 degrees. The same as keys, splines are used to provide a joint connection between the hub and the shaft for torque and power transmission. 002 for shafts 2 to 3 in, inclusive; -0. Adjacent images in the section below show Oct 11, 2019 · A free body diagram analysis of a straight-sided spline system would show the physics is the same — an applied radial load will be supported by a centering force, resulting in unequal tooth load sharing, as with an involute spline. Involute splines, straight splines & Serrations splines can be specified shaped. The function of a spline shaft depends upon the construction and type of spline applied to the shaft. ANSI B92. Sep 20, 2016 · ALBERO SCANALATO AD EVOLVENTEINT/EXT 24Z 2m 30P ISO4156INVOLUTE SPLINE SHAFTSplined Rotary Shafts Jun 8, 2023 · These types can be used in combinations to transfer torque through a system. Spline shafts. Parallel splines have large, straight-sided teeth that resemble machine keys and transmit more torque than involute spline The present paper deals with straight-sided splines as seen in Fig. Design of straight-sided splines are controlled by standards, e. Flexible spline allows some rocking motion whereas fixed spline allows no relative or rocking motion between two Gears Engineering & Design. cation magnitudes of δ = 0 and 40 μm at. 001 in for shafts 3⁄4 to 13⁄4 in, inclusive; of -0. These teeth make more contact with a bushing than the teeth on parallel splines, so these splines are The external spline is varied to obtain the desired fit. The sides of the equally spaced grooves are involute, as with an involute gear, but not as tall. * Tolerance allowed of -0. DIN 5480-1 -- Reference diameters for involute splines and spline joints . ). 025” per side, you should be able to rotary broach the form on your CNC machine. A thorough inspection of each straight Feb 27, 2014 · While this "pre-twist" may result in some interference along the flanks when the spline is unloaded, as soon as the spline is subject to operating loads, the shape of the spline teeth should normalize. The shear stress at the pitch line of the teeth for a transmitted torque T. Jul 28, 2023 · Spline broaches are cutting tools with a series of teeth that progressively increase in size. The profile drawing can be used for profile projector, wire eroding machine, 3D printer etc. WNXE offers various input options: Aug 25, 2016 · Major diameter fit vs. If that is what you want, OK but in real life, it will probably bind. Wikipedia—Spline . IS 2610 – power transmission-straight sided splines for machine tools dimensions. There are numerous types of spline shafts, including, involute splines, which have short, curved, and evenly spaced teeth; parallel splines, which are short, straight sided splines; serrated splines, which are V shaped; and helical splines, which are built for optimal . if you draw up the actual involute spline for a toyota shaft, the side of the spline has roughly a edit* . IS 2327 – Straight-sided splines for cylindrical shafts. They are designed to create precise spline profiles on workpieces. Sep 15, 2020 · According to the American Heritage Dictionary of the English Language, a spline is defined as: Noun: 1a) Any of a series of projections on a shaft that fit into slots on a corresponding shaft, enabling both to rotate together. Splines and serrations are either straight (parallel to the axis of the part) or have a lead (helix angle). The Insert Control Vertex command adds one or more control vertices to style splines. Google on involute spline cutter. Calculated spline length: L f = min {L, Le} [in] Compressive stresses on sides of spline teeth. g. Shaft Diameter: Max 42” swing. Manufacturing of fluted shafts, splines and involute splines from pre-manufactured blanks or from solid with automatically dresset grinding wheel form and dressing cycle. Gear Motions manufactures custom splines to exact specifications. As spline shafting suppliers, AmTech OEM can manufacture a spline shaft with an outer diameter of 0. They are out there. Straight-sided splines are easier to manufacture and may be suitable for lighter loads. Pitch: Max 2. 5 DP. 1b) The groove or slot for such a projection. REQUEST A QUOTE. If the splines are being designed, then one of the preferred pres-sure angles from the standards should be used. 2. Module measurements range from 0. While the geometric form is complicated, modern hobbing, grinding, rolling, and other forms of profile generation make this type of spline easily obtainable, even in a high volume production environment. 1-- Sizes, performance, and inspection of involute splines . Design How for Involute Splines. However, a one-inch diameter form with a . The transfer of this rotation is at a ratio of 1:1. Involute splines can be either Side fit or Straight Sided Serrations: Serrated Shaft Ends – SAE J500; British Straight-Sided Serration Standard; DIN 5480 Inv. fine pitch splines that are case hardened. The notes and tables below relate to straight cylindrical involute splines in accordance with BS ISO 4156:2005-1 Straight cylindrical involute splines. 5/5 to 128/256 and pressure angles of 30°, 37. Involute splines can be either Side fit or Diameter fit. The very simplest method of initially selecting of involute spline based on a shaft dia is to arrive at an initial Pitch circle dia (D) and a module (m). Local edit allows you to drag and manipulate the shape of a style spline without affecting adjacent style splines. We will only be considering involute splines here because they are much more common. Chaplin,1994-01-01 The purpose of this design guide is to provide the designer help in understanding the design, manufacture, and operation of splined shaft connections. 510206. The functions of a typical spline shaft are often undertaken. 1. This has a OD of 25 mm D i reduced dia= 21 mm n = 6 teeth L e: The length of spline selected = 25mm . Spline broaches come in various forms, including involute, straight-sided, and serrated, depending on the specific application. Involute gears pot be either Party fitting or GlobalSpec Product Announcement for Involute Splines vs. Involute Spline is a spline having teeth with involute profiles. This series of standards deals with involute splines and interacting involute splines in the ranges module 0,5 to 10, with a number of teeth ranging from 6 to 82 and a pressure angle of 30°. Mar 1, 2004 · An “involute spline” is one that has a tooth profile form defined by an involute curve, often referred to as the “involute profile. Compared to keyed shafts, they last longer and handle higher torque. Number of Teeth and Pressure Angle Mar 16, 2015 · For example, if you have a half-inch diameter involute spline with tooth height of . ANSI and DIN offer the choice between 30°, 37. Allowable compressive stresses on splines are much lower than for gear teeth, since nonuniform load distribution and misalignment result in unequal load sharing and end Oct 28, 2017 · The pressure angle of a spline is the angle between where the pitch diameter meets the involute curve and a tangent point on the base diameter (fig. 25-10 inclusive, relating to nominal pressure angles of 30 deg, 37. € 84,00. eo fi xd rn mc bm ea be oa um