RodneyFord

Glued in the motor mount. I might need a nose ring yet.

RodneyFord

This block of 7075 high tensile aluminium is going to become 4 engine mount screws.




A new hacksaw blade and some elbow grease.




And we have 4 lumps of aluminium.

RodneyFord

Roughed out the blocks first in the 4 jaw chuck then in the 3 jaw.




Finished off and a 5mm thread cut on the end.




Steel screw.




Same length aluminium. 14gm saving for 4 of them. I was surprised at that.

RodneyFord

Rudder out of the press.

bjr_93tz

Just asking a quick question. You're not concerned about fatigue using a high tensile aluminium bolt in a mount like that?

We (Dad and I) had a Zenoah G62 (horrible, vibrating, petrol thing it was) mounted in a similar fashion and high tensile steel bolts (passing through rubber isolators on each side of the firewall) were breaking one after the other. Every dozen or so flights we'd find another broken bolt. General purpose steel bolts put up with the flexing much better. The DA is a much more refined engine and maybe it's not an issue?

Thanks for the build log...

RodneyFord

Thanks for the heads up. I have lots of flights (300) with DA 85 same setup but standard steel bolts. No problems with the mount but the motor vibrated badly. The whole top of the crankcase sheered off after around 100 flights (also 7075 and replaced under warranty). I replaced it with a DA120 but that vibrates quite a bit too especially at idle. My DA 200 (DA50x4) is sweet though and I think the DA 50 is going to be a nice motor too. Anyway I will keep a close eye on those bolts.

RodneyFord

Interestingly DA use high tensile aluminium fasteners except for prop bolts. When I torqued down the head bolts I used a low setting of 42 oz/in.

RodneyFord

Making a kevlar ballast tube. 19mm tube, mylar held on with petroleum jelly, 3 wraps of 38gm kevlar.




Tight wrap with electrical tape.

RodneyFord

Good weight. Not sure I will use this yet but it is a good option to have.

RodneyFord

Made titanium push rod ends for the 2mm carbon elevator push rods.




3mm titanium bound with carbon tow epoxy and then heat shrink on the servo end. The carbon rods will run in teflon tubes bound to balsa sticks.

RodneyFord

Push rod assembly ready to install.




Teflon tube bound to balsa with narrow ribbon and glued with thin CA.




I will 3D print some exit guides for these.

RodneyFord

Glued in the push rod assembly. Those cross braces added a lot of stiffness.

RodneyFord

I need to get get every thing done apart from the wings and UC so I can determine the balance point.



Setting up the spinner mold.

RodneyFord

Balsa tips on the rudder.




Took them off to hollow them out.




4.9 gm saving.

kenh3497

I set up an old Goldberg Bucker Jungmann with dual carbon pushrods. Instead of binding the two pushrods into a single rod at the front, I used a ball joint on each rod and put a ball on each side of the servo horn. So far it is working well.

Ken

RodneyFord

Hi Ken that would work and balance the forces. Here is my Bucker Jungmann ZDZ 120 on twin pipes. Actually that was the last aluminium brazing I did. But I am about to make a canister muffler for Zeus.



Sig dope finish.

RodneyFord

Something like this.




Fitting the exhaust header.



Silver soldered to the flange. I will fit the canister to this, It will be a series of cones and tubes nothing like a commercial item.

RodneyFord

Made a titanium tail wheel assembly. Also glued in the tail post and the ballast tube.

RodneyFord

Spinner mold half.

RodneyFord

Could refine down the retaining plate.

RodneyFord

!/2" balsa tail post suitably lightened.




8mm balsa cap, beveled.

RodneyFord

Started playing around with my sheet metal program.

RodneyFord

After quite a few versions I have arrived at this. You can probably see a tuned pipe influence as I have made a lot of them. I know what works for me in terms of assembling and brazing. This will have 4 chambers.

kenh3497

You must have read the "Two stroke Tuners Handbook. http://www.amrca.com/tech/tuners.pdf

The pipe looks good!

Ken

RodneyFord

Yes Ken that has been my go to manual for years. However it is somewhat superseded now as they have worked out how to use a Helmholz resonator for significantly more boost. That is why you see such fat tuned pipes on the latest 2 strokes. I considered a helmholz resonator for active silencing on this setup but I need to know the frequency to design it at so that will need to wait. I wont need a tuned pipe on the Zeus as the DA 50 should have plenty of power without it.