daddywoofdawg
Member
to me it seems like you have un-needed extra weight with the Y connection set up;you have the poles for the Y and the connectors for same.as far as the esc is there room to mount them on the outside of the battery box?
X8 Design Study
- Thread starter Simspeed
- Start date
Hi Daddywoofdawg...thanks for your comments. You know relocating the ESCs to the outside of the battery box was the first option I looked at. The space between the batteries and the side plates seemed like a usable space but the ESCs shown are just too big to fit there. We could go with something smaller but the design needs to be able to accommodate bigger motors and large props which will necessitate higher amp rated ESCs. Besides, the utility of the battery box location just didn't fit the design goal of the project which is compactness and simplification to fit the folding travel case. By relocating them to the top of the arm braces I think that problem is solved and just about any size ESC can be placed there.
The case has a 10" dia. inside envelope that the folded frame and components must fit. Length of the case can be whatever need is determined for the largest fitting props.
View attachment 17209 The drawing here shows the case length at 12cm with 28" props mounted. I plan to 3D print the cap, base and hinge parts for the case; the arms will be cut with a water jet from standard 10' PVC pipe if nothing more suitable is found. Should be pretty tough and durable.
The aluminum Y connection and the rod ends comprise the majority of weight of the frame. However, the mechanical functionality of the design necessitates geometric rigidity which those parts provide. Considering the weight of the bare frame with these parts is calculated to be 1882 grams, I think the strength/weight ratio is within reason for an X8 28"+ prop multirotor. This combination with 1900g of motors, 28" props, 3150g of 24 Ah batteries, foldable landing gear, wired and ready to fly is calculated to weigh an even 10kg. That compares favorably with the 10kg weight Ferdinandk quoted elsewhere for his big 28" rig with 4kg batteries.
It would be nice to lower the weight where possible. but the compactness and portability of a folding frame design like this means it's not going to be a featherweight. I just need it to be comparable to other multi-rotor combinations with like equipment options and payload capabilities. Thanks again....TP
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Well I gave some serious consideration to Daddywoofdawg's comments about the extra weight of the Y connection in the arms. I did some research on ways to make strong CF tube connections without metal lug as shown in my drawings. The bike builders have the fab solution that goes back to fitting mitered tube joints I'm familiar with from my race chassis building days. Fit and sleeve the joints internally, tack weld with epoxy and blend the joint radius for surface bonding with wetted unidirectional CF strips. The upright arm bracket connecting three tube section with the brace tube at the female clevis, will be 1/4" CF plate bonded to an internal sleeve as shown in this x-ray drawing.
View attachment 17364View attachment 17360
The tubes can be notched and fitted on an alignment jig while the CF layup is applied and cured. I've located a reasonably priced 3D printer with a 15X14X13 build envelope. That's plenty big enough to make parts for a jig fixture to construct the arms and the cap and hinge base for the carrying case. I think I can print all the frame fittings out of nylon and assemble the corner post with aluminum nuts and washers cut from thick wall CF tube. It's more work certainly, but eliminating and replacing the metal fittings where possible with dense nylon produces a substantial weight savings. All the arm connections are in compression so I don't think there will be a problem using nylon for the connections.
I redesigned the corner hinge joints to better distribute the weight stress through the pivot shafts into the frame, and bulked up the battery box and gimbal hanger fittings for the same reason.
View attachment 17361View attachment 17362View attachment 17365
With these changes the weight of the bare frame calculated out to 1490 grams down from 1882. Ready for flight less batteries, the rig should weigh 5811 grams. As designed the box will carry 2ea 6s 12000 mAh Gens Ace batteries which the mfg quotes at 3153 grams. I used their dimensions to size the frame around the batteries for a tight fit with the least frame structure possible. So frame, remote folding landing gear, motors, 20 - 28" props, and control electronics we're in the neighborhood of 9Kg less payload which for me will be about 2.75Kg. Almost 26 lbs AUW.....glad my flight times won't be very long.
View attachment 17364View attachment 17360
The tubes can be notched and fitted on an alignment jig while the CF layup is applied and cured. I've located a reasonably priced 3D printer with a 15X14X13 build envelope. That's plenty big enough to make parts for a jig fixture to construct the arms and the cap and hinge base for the carrying case. I think I can print all the frame fittings out of nylon and assemble the corner post with aluminum nuts and washers cut from thick wall CF tube. It's more work certainly, but eliminating and replacing the metal fittings where possible with dense nylon produces a substantial weight savings. All the arm connections are in compression so I don't think there will be a problem using nylon for the connections.
I redesigned the corner hinge joints to better distribute the weight stress through the pivot shafts into the frame, and bulked up the battery box and gimbal hanger fittings for the same reason.
View attachment 17361View attachment 17362View attachment 17365
With these changes the weight of the bare frame calculated out to 1490 grams down from 1882. Ready for flight less batteries, the rig should weigh 5811 grams. As designed the box will carry 2ea 6s 12000 mAh Gens Ace batteries which the mfg quotes at 3153 grams. I used their dimensions to size the frame around the batteries for a tight fit with the least frame structure possible. So frame, remote folding landing gear, motors, 20 - 28" props, and control electronics we're in the neighborhood of 9Kg less payload which for me will be about 2.75Kg. Almost 26 lbs AUW.....glad my flight times won't be very long.
