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| Scale Helicopters Discuss scale helicopters, tips, tricks and scale construction threads |
Topic Review (Newest First)
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| 02-20-2016 10:06 AM | |
| Gizmoman |
Re: Schweizer 300C The bearings were secured in the drive shaft guides with CA. Locktite 7471 primer was applied to the torque tube. The shaft guides were spaced at unequal distances along the torque tube and a small drop of green wicking threadlocker was applied at the tube and bearing junction. Twenty four hours later the bearings are solid. The claw connector was installed on the torque tube and the complete assembly slid into the tail boom. The drive train turns smoothly and the only lost motion I can detect is in the tail rotor gear mesh. Out of curiosity, I clamped a length of 2mm drive drive in a vice. With vice grips on the other end I started twisting the wire. Using only light pressure I easily went 1 1/2 turns. Going two turns didn't take much more effort. The only bespoke parts for the conversion are the delrin bearing mount and retaining collar. An alternative to the delrin part might be using several of 17/19 PVC sleeves placed end to end. The retaining collar is just added insurance since the shaft is retained in the bearings with threadlocker. The conversion is finished and the complete unit will be test run on the Benzin before installing on the Schweizer. I'll do an update when the Schweizer is flown again. Time to get the Benzin completed. G |
| 02-20-2016 09:01 AM | |
| Gizmoman |
Re: Schweizer 300C I was cleaning the torque tube and bearing IDs before assembly and a recent mishap came to mind. An acquaintance experienced a mechanical failure when a threaded stainless steel stud came loose from an anodized component. It was assembled by the manufacturer and there was evidence that a threadlocker compound had been applied. My acquaintance's mishap got my attention because the materials are common in our hobby. So what happened? The wrong threadlocker was used with inactive metals. The text in quotation marks is from the Locktite web site. "We recommend the use of primers such as 7649 & 7471 with most anaerobics where both parts are classified as "inactive" metals. These metals lack the presence of iron or copper content and thus, lack the "active" metal ions required to fully cure the product in 24 hours. These metals include plated parts, stainless steel, galvanized steel and anodized aluminum, to name a few. If, on the other hand, both or at least one part is an "active" metal, such as plain steel, brass, bronze, copper or iron, there is no need to use a primer to ensure full cure in what is typically 24 hours at room temperature." I've used Locktite 242 (blue) and Locktite 290 (green wicking) for many years and threadlocker would not cure when securing bearings to torque tubes. Now I know why. I've bought some 7471 primer to use on this torque tube assembly. It's an aerosol can containing some nasty ingredients so it's outdoor use only. Instead of Locktite 242, I'll be using Locktite 243 which gives primerless performance on both inactive and active metals. G |
| 02-19-2016 08:14 PM | |
| Gizmoman |
Re: Schweizer 300C Yes, please post more pictures. G |
| 02-19-2016 05:28 PM | |
| desmonds |
Re: Schweizer 300C Hi Peter Des here finally got the Schweitzer done ,had the first flight ,It flew perfect no surprises going to try to send you some pics if I can figure out how to do it |
| 02-19-2016 01:50 PM | |
| Gizmoman |
Re: Schweizer 300C The tail rotor assembly needed the 2mm wire input shaft changed to a claw connector style.   A drive shaft guide was added to the long torque tube section and inserted into the tail boom. A slight twist and the dog bone was fully seated into the socket of the articulated coupler. There is a leather disc inside the socket that prevents metal to metal contact. The tail rotor mount was installed on the tail boom and the tail rotor assembly onto the torque tube. The distance (+1mm) between the mating surfaces of the tail rotor mount and tail rotor housing is the length by which the torque tube is shortened.  After the edge was squared, a knurled insert is bonded inside the torque tube. These knurled inserts prevent the torque tube from being crushed when tightening the coupler set screws.  These are the Vario parts used for the conversion. 1- 17/16 - 6mm x 950mm torque tube 1- 17/19 PVC sleeve - package contains 3 boom guides 5- 17/22 - ball bearing 6 x 13 x 5 1 - 49/61 - articulated gear box connector 1- 49/63 - articulated joint (pairs with 49/61) 2- 49/8 - cruciform element 2- 49/7 - claw connector 2 - 17/17 - connecting plug for 6mm tube 1 - 49/12 - claw connector on 5mm shaft G |
| 02-19-2016 06:54 AM | |
| Max |
Re: Schweizer 300C Fantastic solution so far. Looks great |
| 02-18-2016 08:13 PM | |
| Gizmoman |
Re: Schweizer 300C The intermediate shaft assembly was then coupled to the tail drive's claw connector and the assembly pushed into the short tube section.   Measurements were taken to calculate the position of the bearing mount relative to the inboard face of the boom clamp. The dimension was transferred to a push tube and the shaft assembly was then pressed into the Schweizer tail boom. The bearing mount is a firm press fit but I added a 2mm screw just in case.  I now need the tail rotor assembly from the Schweizer in order to prepare the second torque tube. G |
| 02-18-2016 11:54 AM | |
| Gizmoman |
Re: Schweizer 300C Hi Guys; The helicopter was suitable to fly but I want solid yaw control. In its current state it doesn't have the performance we've come to expect from a modern gyro and servo. A bit more work done. Two straight edges positioned against the inner surface of the alignment blocks showed the centre line of the bend and alignment marks were drawn on the jig board.  A short tube was installed in the boom clamp and the original tail boom placed in the jig on the other side of the bend.The delrin bearing mount was pressed into the short tube section. Shaft guides were installed inside the long tail boom and the torques tubes with couplers inserted. Measurements made and the intermediate shaft was cut to length.  The bearing mount, intermediate shaft, and couplers were assembled. A retaining collar was added to ensure there's no end float in the torque tube.  I've run out of Locktite so off to the store I go. G |
| 02-18-2016 08:59 AM | |
| Keyrigger |
Re: Schweizer 300C It's such a shame that you had the trouble with the tail. I know of three individuals that have built and successfully flown (for many years) that helicopter and if something had been mentioned, I would have either asked them what they did or put you in contact with them. I am sure, though, that your modification will be bulletproof. Hope to see you sometime soon. Don |
| 02-18-2016 08:17 AM | |
| Max |
Re: Schweizer 300C Wow. That is going to be some mod, Peter. Looking forward to seeing what comes out of this idea. |
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