New prototype Gasser T-rex 700E DFC V3

[martin_]

Well, I took some time yesterday to build a prototype Gasser conversion I drew, as the tittle says it's based on the latest T-rex 700E V3, stock zenoah clutch set-up and fully adjustable mount to use 15T to 22T pinion if wanted, it's as easy as to simply slide the motor & bottom frame assembly to the longitudinal axis to adjust the gear mesh.

The prototype is laser cut out of 2.0mm aluminum to see if all fit well. I had to make some additional modification because there was some interference here and there, but now it's perfect. The final product will be made with G10 2.3mm but still an 3mm aluminum bottom frame (6061 T6 is used). The thick bottom plate is to add rigidity to the adjustable assembly, but that was not an easy task because I encountered some misaligment issue and it took some time to figure out what was wrong.

When I took all the measurement to CAD the requiered parts and hand made some rough parts trying to fit the motor, I noticed...... better said I found later that the RC format motor does not sit perpendicular to the vertical axis of the main frame when it's bolted to a rigid plate, the 4 mounting tabs on the fan cover does not have an equal thickness, therefore the best method to use these motor are to use a soft/flexible bottom plate, however if a rigid plate is used, some shims are requiered. The off axis is not by much, but it made a large difference when translated to the end of the crank shaft, it's no more centered between the frame, if so, it's centered but at an angle.

Just a tip to everyone who want to ''home made'' a rigid bottom frame based on the measurement took on an existing kit, to save some head scratching, you must first properly align (shim) the motor to the ''soft'' plate, but by doing this the end of the cranck shaft will move and the mounting hole for the landing skid will no more align, you have to relocate it by the same amount that the end of the crank have moved, and obviously the motor will sit a little higher and may cause problem trying to fit it on the frame. If no shim are used, the end of the crank can be well centered between the two frame, but at an angle, and may cause vibration issue if the clutch is not attached to the motor.

Anyway, all this are only a few millimeters here and there that are compensated by flexible parts when you mount a kit, but when we work the measurement in CAD, the program does not know that the parts have to flex.

Here is some photo, sorry for the quality, I took it with my phone and I do not have much skill in photography.

[fastflyer20]

Your project looks very interesting. What pinions and bell clutch housing are you using? Have you run the reed valve engine yet?

[martin_]

No, I don't have started the engine yet, it's too cold here anyway, and with 5+ foots of snow already.

Pinion are from a store in UK, available from 10T to 130T I think, and with different module if nneded.

Clutch housing is standard CY/Zenoah, the Clutch holder is from HPI Baja, with a Redcat rc car clutch bell.

[DEDO]

Hi Martin,
Great work!
This is what this Hobby is about! Ideas to Prototype.
Are you using Aligns cyclic servo mount?
Regards,Robert

[martin_]

Dedo, yes, I agree with you that this hobbies is ideas & etc..

The new bearing bloc have the servo mount molded in it, so it's a 2-in-1 parts.

[ADozer]

Absolutely beautiful work.

[Doug Darby]

Very Nice work Martin...
I think you have a great combo here with your clutch choice and adjustability of gear ratio. Keep us updated on how things go...

[martin_]

Thanks and happy new year to all..!!

There is severals hours in that project and I have put a couple more to modify the design and some fitment here and there, but now it's almost perfect.

Two of my friend will use that kit to build a gasser also, at the end I will make 10 kit in total since it's not much more expensive, which mean I will have a few for sale if someone is interested.

Parts availability is not a problem since it use already existing parts, other than the frame itself & motor mount.

[martin_]

I finally received the finished parts today, 10 Kits in total.

I'll add photos as construction progresses.

[jockstrap]

wow - looks great, congrats on finally getting the first kits in..

Hope it all goes well.. can't wait to hear the results..and to see the build..

[martin_]

Thanks. So far, all goes well, it's based on the aluminum prototype with some modification.

Here some pic of the clutch, mount and pinion assembled on the engine.

[jimIII]

Am I missing the clutch shoes? Are you using the Zenoah style clutch shoes?

I figured it out with a little research: Lauterbacher 4 Shoe Clutch. I need to read up on this, looks interesting!

[martin_]

Yes, that is an Lauterbacher clutch, useless other than to save weigh, it's only 75 grams opposed to 150 grams for the stock zenoah clutch.

Ok, some more photo of the build;

[martin_]

700 look or 800 Trekker look?

[FastRunner]

nice kit, Martin.
Let us know final dry & flying weights.

[jimIII]

Your anti-rotation guide is a nice improvement in the direct to swash set up. My friends and I have bent more elevator bell cranks than you can shake a stick at. Hopefully, the servo gear sets will hold up!

[martin_]

Bahh..... the antirotation bracket is how the Electric T-rex 700 is, I can't get the credit to that.

For the weight, this is with Align 800 main blade, the large Trekker canopy, heavy Quick-uk landing gear & the reed case crankcase, I just weighted it at 13.5lbs without pipe or muffler but everything needed to fly, no fuel of course.

[cbrum11]

Fantastic looking build. I know this is an old thread but I hope it all worked out for you.

Quick question, would you mind sharing the dimensions of the two bearings you used both below and above the hpi baja clutch bell mount?

I found the dimensions of the bearings that normally come with the mount. I also found the dimensions of the bearings normally used with that redcat clutch bell. The two appear to be different though, so I'm wondering which you went with.

Thanks!

[Khosravi]

I've always wondered this too! I could not for the life of me find the right size bearings!
Martin, you don't happen to still have a kit for sale do you? If so, put me in line for one

[martin_]

I dont have the bearing right in my hand to give you dimension, but I used bearing that have OD to fit the HPI holder and ID to fit the redcat clutch, If I remember, there was one weird size that I could only find on Boca bearing website.

I still have 2 or 3 kit that I can sell for very cheap if someone want one, or sell averything I have related to this for a good price, so this will give spare if you crash, I can also give you for free the CAD files of everything related if one want.

Edit: I still have the Mielke modified tuned pipe pictured above, I paid very high price for it, but can sell it for cheap, a little hard to tune but very powerfull, and much quieter than any other sort of muffler.