[{"data":1,"prerenderedAt":505},["ShallowReactive",2],{"\u002Fen\u002Fblog\u002Fjoint-motor-selection-guide":3},{"id":4,"title":5,"alt":6,"author":7,"body":8,"date":493,"description":494,"extension":495,"image":496,"keywords":497,"locale":498,"meta":499,"navigation":500,"path":501,"seo":502,"stem":503,"updated":498,"__hash__":504},"blog\u002Fblog\u002Fen\u002Fjoint-motor-selection-guide.md","BXI 85\u002F70\u002F50 Joint Motor Selection Guide (with full spec table)","BXI Robotics joint motor lineup","BXI Robotics",{"type":9,"value":10,"toc":481},"minimark",[11,16,20,25,269,280,284,287,329,333,354,358,386,390,410,414,428,432,435,439,445,451,457,463,469],[12,13,15],"h1",{"id":14},"bxi-857050-joint-motor-selection-guide","BXI 85\u002F70\u002F50 Joint Motor Selection Guide",[17,18,19],"p",{},"BXI Robotics joint motors use a hollow-shaft planetary reduction design, with dual absolute encoders (magnetic input + inductive output) and cross-roller bearings across the lineup, plus MIT-protocol-compatible CAN\u002FCANFD communication. The actuators have been stress-tested under extreme conditions on multiple humanoid platforms, and their modular design fits both robotic arms and legs in high-DOF embodied systems. This guide gives the full specs of the four main models, a breakdown of what each parameter means, and a practical workflow so engineering and procurement teams can select by torque and size.",[21,22,24],"h2",{"id":23},"full-spec-table","Full spec table",[26,27,28,50],"table",{},[29,30,31],"thead",{},[32,33,34,38,41,44,47],"tr",{},[35,36,37],"th",{},"Parameter",[35,39,40],{},"BXI8515-19",[35,42,43],{},"BXI7010-19",[35,45,46],{},"BXI5018-19",[35,48,49],{},"BXI5014-19",[51,52,53,71,88,102,116,130,146,160,177,193,210,226,241,255],"tbody",{},[32,54,55,59,62,65,68],{},[56,57,58],"td",{},"Rated torque",[56,60,61],{},"40 N·m",[56,63,64],{},"15 N·m",[56,66,67],{},"11 N·m",[56,69,70],{},"7 N·m",[32,72,73,76,79,82,85],{},[56,74,75],{},"Peak torque",[56,77,78],{},"150 N·m",[56,80,81],{},"50 N·m",[56,83,84],{},"35 N·m",[56,86,87],{},"25 N·m",[32,89,90,93,96,98,100],{},[56,91,92],{},"Rated voltage",[56,94,95],{},"24–48 V",[56,97,95],{},[56,99,95],{},[56,101,95],{},[32,103,104,107,110,112,114],{},[56,105,106],{},"No-load speed",[56,108,109],{},"200 rpm",[56,111,109],{},[56,113,109],{},[56,115,109],{},[32,117,118,121,124,126,128],{},[56,119,120],{},"Rated output speed",[56,122,123],{},"100 rpm",[56,125,123],{},[56,127,123],{},[56,129,123],{},[32,131,132,135,138,141,144],{},[56,133,134],{},"Peak phase current",[56,136,137],{},"90 A",[56,139,140],{},"60 A",[56,142,143],{},"30 A",[56,145,143],{},[32,147,148,151,154,156,158],{},[56,149,150],{},"Reduction ratio",[56,152,153],{},"19.5",[56,155,153],{},[56,157,153],{},[56,159,153],{},[32,161,162,165,168,171,174],{},[56,163,164],{},"Weight",[56,166,167],{},"1.4 kg",[56,169,170],{},"0.8 kg",[56,172,173],{},"0.55 kg",[56,175,176],{},"0.5 kg",[32,178,179,182,185,188,191],{},[56,180,181],{},"Installation diameter",[56,183,184],{},"99 mm",[56,186,187],{},"81 mm",[56,189,190],{},"64 mm",[56,192,190],{},[32,194,195,198,201,204,207],{},[56,196,197],{},"Height",[56,199,200],{},"73 mm",[56,202,203],{},"68 mm",[56,205,206],{},"70.5 mm",[56,208,209],{},"66.5 mm",[32,211,212,215,218,221,224],{},[56,213,214],{},"Hollow bore",[56,216,217],{},"10 mm",[56,219,220],{},"9 mm",[56,222,223],{},"6 mm",[56,225,223],{},[32,227,228,231,234,237,239],{},[56,229,230],{},"Encoder",[56,232,233],{},"Dual absolute (magnetic input + inductive output)",[56,235,236],{},"Same",[56,238,236],{},[56,240,236],{},[32,242,243,246,249,251,253],{},[56,244,245],{},"Bearing",[56,247,248],{},"Cross-roller bearing",[56,250,236],{},[56,252,236],{},[56,254,236],{},[32,256,257,260,263,265,267],{},[56,258,259],{},"Communication",[56,261,262],{},"CAN \u002F CANFD",[56,264,262],{},[56,266,262],{},[56,268,262],{},[270,271,272],"blockquote",{},[17,273,274,275,279],{},"Values are theoretical; actual values may vary by operating conditions. The first two digits denote the frame-size series (85\u002F70\u002F50), and the ",[276,277,278],"strong",{},"-19"," suffix corresponds to the ~19.5 reduction ratio.",[21,281,283],{"id":282},"how-to-read-the-key-parameters","How to read the key parameters",[17,285,286],{},"Understanding a few parameters up front avoids trial-and-error over \"is the torque enough\":",[288,289,290,305,311,317,323],"ul",{},[291,292,293,296,297,300,301,304],"li",{},[276,294,295],{},"Rated vs peak torque:"," rated torque is what the motor can output continuously — use it for sustained holding and steady-state loads; peak torque is the short-duration ceiling — use it for start-up, impact, and dynamic swings. Keep ",[276,298,299],{},"continuous operation within rated torque"," and ",[276,302,303],{},"reserve peak torque for transients",".",[291,306,307,310],{},[276,308,309],{},"19.5 reduction ratio:"," the whole lineup uses a 19.5 planetary ratio, trading speed for torque — output speed is about 1\u002F19.5 of motor speed, which is why rated output speed is a uniform 100 rpm. A common ratio means torque scales mainly with frame size, so selection comes down to matching a \"torque tier\".",[291,312,313,316],{},[276,314,315],{},"24–48 V rated voltage:"," compatible with common robot bus voltages and reusable across 24 V and 48 V systems.",[291,318,319,322],{},[276,320,321],{},"Peak phase current:"," reflects the current the drive must supply — larger frames demand more (90 A on the BXI8515-19) — size your power supply and drive headroom accordingly.",[291,324,325,328],{},[276,326,327],{},"Weight and end-effector inertia:"," joints closer to the end (wrist\u002Fhand) should use lighter models; lower end inertia helps dynamic response and energy use — the 5014\u002F5018, as light as 0.5 kg, are built for exactly this.",[21,330,332],{"id":331},"a-three-step-selection-workflow","A three-step selection workflow",[334,335,336,342,348],"ol",{},[291,337,338,341],{},[276,339,340],{},"Set the torque tier:"," estimate the continuous holding torque and peak impact torque in the worst-case pose, then shortlist models — match holding torque to rated torque and impact torque to peak torque.",[291,343,344,347],{},[276,345,346],{},"Check size and weight:"," among models that meet the torque requirement, prefer the smaller-diameter, lighter one — especially for distal arm joints — to cut inertia and overall weight.",[291,349,350,353],{},[276,351,352],{},"Verify routing and interface:"," confirm the hollow bore can carry your cables and sensor wiring (6–10 mm options), and standardize CAN\u002FCANFD communication and bus voltage.",[21,355,357],{"id":356},"how-to-choose-match-torque-to-joint-location","How to choose: match torque to joint location",[288,359,360,369,377],{},[291,361,362,365,366,368],{},[276,363,364],{},"High-torque leg joints (hip\u002Fknee):"," choose the ",[276,367,40],{}," (150 N·m peak) for sufficient support and dynamic torque.",[291,370,371,365,374,376],{},[276,372,373],{},"Primary arm joints (shoulder\u002Felbow):",[276,375,43],{}," (50 N·m peak) to balance torque and weight.",[291,378,379,365,382,385],{},[276,380,381],{},"Lightweight distal joints (wrist\u002Fend):",[276,383,384],{},"BXI5018-19 \u002F BXI5014-19"," (35 \u002F 25 N·m peak), as light as 0.5 kg to reduce end-effector inertia.",[21,387,389],{"id":388},"core-technology-hollow-shaft-dual-absolute-encoders-cross-roller-bearings","Core technology: hollow shaft + dual absolute encoders + cross-roller bearings",[288,391,392,398,404],{},[291,393,394,397],{},[276,395,396],{},"Hollow-shaft planetary reduction:"," the large-diameter hollow output frees routing space for cables, hydraulics, and sensor modules, greatly simplifying whole-robot wiring and increasing joint range of motion; planetary reduction balances torque density with a compact structure.",[291,399,400,403],{},[276,401,402],{},"Dual absolute encoders:"," one absolute encoder on each of the input and output sides measures the true output angle directly, delivering higher closed-loop control accuracy and enabling power-on without homing — the joint position is known at boot, with no zeroing routine.",[291,405,406,409],{},[276,407,408],{},"Cross-roller bearings:"," a single bearing handles radial, axial, and moment loads simultaneously, improving joint stiffness and rotational accuracy — ideal for load-bearing joints.",[21,411,413],{"id":412},"communication-and-control-cancanfd-mit-protocol","Communication and control: CAN\u002FCANFD + MIT protocol",[17,415,416,417,422,423,427],{},"The whole lineup uses CAN \u002F CANFD and is MIT-protocol compatible, supporting hybrid torque \u002F speed \u002F position control for high-bandwidth, low-latency multi-joint coordination on a single bus. On high-DOF robots, pair them with the ",[418,419,421],"a",{"href":420},"\u002Fen\u002Fmotors\u002Fcontrol-modules","PCIE-CAN control modules"," (up to 24 CAN buses, 1 kHz control) for centralized scheduling; the ",[418,424,426],{"href":425},"\u002Fen\u002Fblog\u002Felf3-humanoid-robot-specifications","Elf 3 humanoid robot"," uses a PCIE-CANFD architecture to reach a >1000 Hz whole-robot control rate.",[21,429,431],{"id":430},"validated-on-whole-robots","Validated on whole robots",[17,433,434],{},"These actuators are more than spec sheets — the 85\u002F70\u002F50 series has been stress-tested under extreme conditions on multiple humanoid platforms and serves as the power source for all 31 joints of the Elf 3, spanning everything from load-bearing legs to dexterous arm manipulation.",[21,436,438],{"id":437},"faq","FAQ",[17,440,441,444],{},[276,442,443],{},"What is the torque range?"," Rated torque 7–40 N·m and peak torque 25–150 N·m across the lineup, covering joints from end-effector to leg.",[17,446,447,450],{},[276,448,449],{},"How do I use rated vs peak torque?"," Select by rated torque for continuous holding and steady-state loads, and by peak torque for start-up, impact, and dynamic swings — leaving headroom for safety.",[17,452,453,456],{},[276,454,455],{},"Which protocols are supported?"," CAN \u002F CANFD, MIT-protocol compatible, with hybrid torque \u002F speed \u002F position control.",[17,458,459,462],{},[276,460,461],{},"Why dual absolute encoders?"," Both input and output sides measure the true angle directly, improving closed-loop accuracy and enabling power-on without homing, which simplifies calibration.",[17,464,465,468],{},[276,466,467],{},"Which model for arms vs legs?"," Use the BXI8515-19 (150 N·m) for load-bearing leg joints, the BXI7010-19 (50 N·m) for primary arm joints, and the BXI5018-19 \u002F BXI5014-19 for lightweight wrist\u002Fend joints.",[17,470,471,472,476,477,304],{},"For selection advice or samples, ",[418,473,475],{"href":474},"\u002Fen\u002Fcontact","contact us"," or see the ",[418,478,480],{"href":479},"\u002Fen\u002Fmotors\u002Fadvanced-motors","joint motors page",{"title":482,"searchDepth":483,"depth":483,"links":484},"",2,[485,486,487,488,489,490,491,492],{"id":23,"depth":483,"text":24},{"id":282,"depth":483,"text":283},{"id":331,"depth":483,"text":332},{"id":356,"depth":483,"text":357},{"id":388,"depth":483,"text":389},{"id":412,"depth":483,"text":413},{"id":430,"depth":483,"text":431},{"id":437,"depth":483,"text":438},"2026-06-20","Selection guide for BXI hollow-shaft planetary joint motors (85\u002F70\u002F50 series): peak torque 25–150 N·m, weight 0.5–1.4 kg, 19.5 reduction ratio, dual absolute encoders, MIT-protocol CAN\u002FCANFD — with a practical selection workflow and spec breakdown for humanoid robot arm and leg actuators.","md","\u002Fmotors\u002Fadvanced-motors\u002Fall_1.webp","joint motor, hollow shaft motor, planetary gear motor, robot joint module, torque motor, dual absolute encoder, joint motor selection, humanoid robot actuator",null,{},true,"\u002Fblog\u002Fen\u002Fjoint-motor-selection-guide",{"title":5,"description":494},"blog\u002Fen\u002Fjoint-motor-selection-guide","geWoFGZl9rRuEbxfpEZt7X0pN5n4dbfpQqDqudEC0_s",1782300801423]