RDJeff

My Feedback: (11)

I have a Quadra 75 that has never been run, and have concluded that I need a longer hub extension to fit my plane. I think I can make one on a lathe, but I can't seem to get it off the crank. Can anybody here give me some advice? I've tried very hard, but no luck. TIA!

CK1

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If someone used loctite on it you will have to heat it up with a small torch then try to get it loose. Lefty loosie righty tighty .

Truckracer

My Feedback: (19)

The hubs on my Quadra 75s were always very tight. Heat as suggested. There were several versions of that engine over the years. Some photos might get you more responses.

RDJeff

My Feedback: (11)

Thanks guys! It's good to know that I'm at least on the right track, and not trying to tighten what I think I'm loosening! Before I posted this thread, I heated the hub up with a heat gun, hoping to swell it a bit to get it to turn, with no luck, not hot enough I guess. I'll try a torch on it to bust the LocTite loose. I imagine I'll have to do something to keep the heat off the magneto magnets.

I keep seeing TruckRacer's handle coming up on all of the gas engine sites I've been exploring, that guy covers a lot of ground!

Truckracer

My Feedback: (19)

First, I’m only on RCU and FG. Been around the block a few times and an active RCer since the 60s. I try to only comment about things I have hands on knowledge of.

I own two of those same Quadra 75s you show in the photos. You can heat the hub only towards the prop bolt end and being aluminum it will conduct the heat to the threads. No need to get the the flywheel hot at all though warm is acceptable. You can also protect the flywheel with a wet rag. Put a steel rod through the hole in the hub, support the flywheel from turning and when the hub is hot, strike the rod sharply with a hammer .... in the right direction of course. The hub will come off!

RDJeff

My Feedback: (11)

Certainly no offense was meant TruckRacer, it must have been FG where I kept seeing you pop up. I could tell that you had quite a depth of knowledge on the subject of gassers.

Thank you for the tips on the hub. I will try it the way you suggested. I have been using the nylon rope in the combustion chamber trick to hold the engine, I trust that won't do any damage.

I'm thinking of selling this engine on, and going with something that will fit more easily.

Truckracer

My Feedback: (19)

No offense taken here. I enjoy helping people when I can.

My Quadras are retired. Replaced them with the smoother and more powerful DLE 85. Only issue is balance as the DLE is at least two pounds lighter. The 75 is an excellent engine but its time has come and gone, at least for me. Power difference is considerable going from a 24-10 prop in the Quadra to a 26-10 on the 85.

RDJeff

My Feedback: (11)

Thanks again TruckRacer, I appreciate your input. The sole reason I bought the Quadra was for the nose weight, but it is quite long, forcing the firewall to be relocated. The dummy rotary on my plane weighs just over three pounds, so I'm now wondering how much weight I really need.

I ordered a DLE85 last week, and should have it in the next day or two. and it'll be a much better fit in the plane. I'm considering flying it with a 27 x 10 prop, have you tried this size prop yet?

Along with problems with the plans, this engine puzzle has made this a challenging build, and I've just barely started it!

Truckracer

My Feedback: (19)

I think the 27-10 prop will be too large for the 85. That engine just loves the 26-10 so I’d recommend that for a starting point. I should ask what plane you’re building for these engines. I’ve flown the 75 in a Ziroli Skyraider and also in a number of older Lanier aerobatic planes. Yes, I liked the weight of the 75 in the Skyraider but there are ways around that like building lighter tails .... or heavier dummy engines! The 85 isn’t just a little bit more powerful than the 75, it is a lot more powerful! I mount mine solid to the firewall with standoffs (not using the anti vibe mount) and it still has much less vibration than the 75.

RDJeff

My Feedback: (11)

I'm building a 1/3 scale Fokker DVIII, a WWI fighter with a rotary engine. The longer the prop, the closer to scale in appearance. I've seen that the 26 x 10 is the most mentioned prop, so I'll start with that. What rpm could I reasonably expect with a 26 x 10? I saw in one of the threads that you were running yours without the vibration isolating mount, I gather that has worked out for you.

Truckracer

My Feedback: (19)

Sorry no rpm records. I rarely use a tach and when I do I rarely keep records. Use it as a tuning tool but mostly tune by airframe performance. I understand completely your prop requirements for the WW1 plane. If it were mine, I would start out with a 26-10 because you know it will work well on that engine. After some flight time, you could certainly switch to a larger diameter prop. Maybe something like a 27-8 or 28-8? Xoar makes some nice WWI props. Several styles to choose from. One thing for sure, the 75 would not be happy with those prop sizes where the 85 would love them.

RDJeff

My Feedback: (11)

I understand what you'er saying, and thank you for your input. I've been looking at the Xoar Axial scale props, but it seems they have a limited number of size combinations. I may have to cut one down to suit.