1QwkSport2.5r

How does the Robbe compare to APC? It looks like they have a similar blade shape.

fiery

My Feedback: (2)

Robbe Dynamic propellers are a GRP 'general purpose' sport propeller made in Germany to the highest standards.

Most importantly, they have a solid hub for maximum strength. Rarely seen these days.

I bought a bundle of 20 or so of various sizes a few years ago. They come in grey w/ red tips; or bright orange w/ white tips. "Mild or wild" up front for colour, take your pick. Dave ended up with one in a horse trade we did. No further of my personal cache of Robbe propellers will be released for trades.

Robbe Dynamic propellers have a 'paddle' type blade. That is, while they are of 'scimitar' style, they are a very broad in the blade. The chord is quite thin.

I really like them for sport use at low to medium RPM's. They grab the air well at low RPM's (highly technical description there) and with my 'hack' powered by an MVVS .49 (8 c.c.) in flight performance improved appreciably with an 11 x 5 Robbe Dynamic installed as opposed to an APC clone (black) 11 x 7. It is quieter as well.

I have never seen them for sale anywhere. I obtained mine from a source in Flemish Belgium. With the rise of electric power for models I don't think they have been made for some time.

1QwkSport2.5r

Duly noted Fiery. If I ever happen to come across one, I'll nab it. Not likely to find it, but hey... Stranger things have happened.

I like APC primarily because they're readily available and more efficient than MA props, though not as durable as MA props.

Hobbsy

My Feedback: (102)

It definitely has an advantage over the APC as they are not efficient below 9,000. This was discovered when guys tried to use APC's on the geared RCV engines.

1QwkSport2.5r

Fair enough. Thanks.

1QwkSport2.5r

I went digging through a box of used engine stuff at one of my local shops and found this gem in the pile. It so happens I have an engine that it fits, so hopefully the engine is in decent shape to actually run. The engine came to me in pieces with horribly rusted bearings... It's for an OS FSR .25 and I nabbed it for $5 NIP. It came with a decal sheet even! I imagine this head has been around awhile...

Hobbsy

My Feedback: (102)

Here is the precious little cutie now.

1QwkSport2.5r

I got a huge box full of engines in the mail today and in that box contained an LA .25 that looks mint - low run time. Got a few other .20 sized glow engines, too.. Gonna catalog the box to see what's there later. If anyone has an LA .25 diesel head they'll part with, let me know. I haven't checked to see if an FSR .25 head will fit, but I have my doubts.

Got another .20 and .65 sportster too... I can diesel the .20, but I don't have a diesel head for the .65 yet.

1QwkSport2.5r

I tried to pirate a piston from another one of my junk lapped .25s with no luck to Frankenstein my FSR into a better running diesel. I do have a Brat .25 in my latest box of goodies that needs a little bit of work, but has similar head dimensions as the FSR .25. The Brat just needs a wristpin retaining clip and it's a good diesel candidate. It hasn't been run much - probably due to the missing g-clip. It's AAC construction with fantastic piston/liner fit, so maybe I'll dieselize the Brat .25 instead. I just need to make sure the screw holes line up.

aspeed

Funny that you mention the Brat .25 with a missing G clip. I have one on the junk shelf (the drawer is reserved for the better ones) with a scored piston/liner where the G clip came off. We used to make replacements from pen springs rather than order them.

1QwkSport2.5r

Yeah, it seems these wire circlips have a tendency to remove themselves from the piston (had a Fox .40 do this numerous times) or break the little "tail" off and cause problems. On my brat, I did what I've done on several engines with good success (mainly junky engines with no hope of ever getting new parts for). Take a small hardened C-clip and insert into the piston in the circlip groove. Pack JB Weld on top of the clip so the wristpin boss is filled flush with the piston. Let cure for 24hrs and run it. The JB holds up to diesel and glow alike. So I did the same thing with the brat. I also found because it was turned over with the pin protruding and kicked a port, I checked to see if the rod was bent while I had it apart and it indeed was bent. So the rod is now straight, the wristpin will never come out, and I measured the Davis head to ensure it will work without modification and as luck would have it, everything is A-OK. So once the JB cures, I'll break in the Brat on glow fuel and get some baseline numbers before converting to diesel. In comparing the Brat to the FSR .25, the carb on the Brat is 7mm while the FSR is 6mm. This should make for some interesting results I think.

1QwkSport2.5r

Got a used K&B Sportster .28 in the mail the other day, so I dieselized it and test ran it a few times. I did a 10x6 APC vs MAS prop comparison as well as ran an 11x6 MAS and a 12x6 MAS.

10x6 MAS 11,220
10x6 APC 11,220
11x6 MAS 9,900
12x6 MAS 7,600

https://youtu.be/BxwDhV-JKnc
https://youtu.be/h444v_M1TXQ
https://youtu.be/39VvLyg_VWo
https://youtu.be/dgbYKzgeB0g

dwrad

Diesel Conversion Enthusiasts,

What I thought was my lifetime's supply of diesel fuel from FAI Supply is running low. Ten or 12 years ago I purchased 16 gallons FAI diesel .

Last I checked the diesel is no longer produced by FAI

1) Where are you guys buying commercial bulk diesel fuel?

2) Has there ever been an effort to pull together a large order from forum members to make it worthwhile for FAI's to knock out a batch?

Thanks in advance

Dave Ward
Altoona, Pa

dwrad

In the prior post I referenced FAI Supply

Sorry, this former source was FHS SUPPLY .....aka Red Max

(they used to make an awesome diesel fuel and cost was really affordable)

Any help on my 2 prior questions much appreciated.

Dave Ward

1QwkSport2.5r

Your only real sources for model diesel fuel that's premixed is Davis Diesel or Eric Clutton's site - Aerodyne maybe? For what it costs to mix my own (about $6-8/qt), I do it that way. John Deere starting fluid is about $4.40/can locally (about 8.5fl oz per can). Castor can be had for around $17/gal and kerosene is easily obtainable from various outlets for $3-4/gal.

dwrad

thanks for the reply. I have enjoyed watching your videos and in fact that's how I returned to RC Universe, which I joined in 2008, but only now actively posting. I believe one of your videos referenced your RCU threads.

I have about 25 diesels give or take, half are purpose built and the other half are Davis diesel conversions. I concentrate in the K&B Sportster series and have multiple running examples in all four displacement sizes. As you note on your videos, once these K&B's are properly broken in, they are truly great runners once dieseled. the only component that I wear out are the connecting rods, but that's usually after 50 hours on a properly run dieselized engine. Those con rods are cheap and easy to replace.... So no problem. As an example I have a 19-year-old Sig Lt-25 I built, powered with a KB 28 with DD conversion head and covered in silk and dope, – and the plane is still going strong with over 150 hours of logged flight time . ( several rebuilds though for new con rods.)

I have had really good luck running the FHS Supply Red Max diesel fuel, but as I mentioned earlier I am nearing the end of my inventory. I don't mind mixing so I might try your suggestion.

Are your fuel components just the John Deere ether/kerosene/castor oil? .... or are you using a pinch of cetane booster? I can live with $24 – $32 a gallon :-)

best regards,
Dave Ward

1QwkSport2.5r

My latest brew was 23% castor, 31% John Deere ether as it comes from the can, 46% kerosene or Jet A, and 2% Amsoil Cetane Boost. That makes 102%, but it fits the Sunnyside acetone cans I use.

Thanks for the kudos. I'm still new to diesels, but I'm getting the hang of it. I have Davis heads for the K&B .20/.28 and .45, ST .45, Fox .50 (though I'm trying to sell it as I dumped my last Fox .50), K&B .40, OS .25 FSR (a $5 find at a LHS last summer!!), and maybe one other one. I'll be testing a used K&B .45 I have as soon as Mecoa gets off their ass and sends me an invoice for a rod. I doubt they will sell me anything - Randy accused me of stealing from our gracious government. A jewel he is!

I got a used .45 in a large lot of engines. The rod's big end is so egged out its not funny.

dwrad

sounds like you are amassing quite the KB collection as well. I believe they are good engines (and really great running diesels with the Davis heads) .. and for the most part they are generally underappreciated.

Thanks for your diesel brew recipe.I want to try this.

Where can I find castor oil by the gallon as you referenced for about $17? is there an online supplier, or what types of common retailers would handle at this price.?

Thanks !
Dave

1QwkSport2.5r

Dave - I do have a small collection of Sportsters - 3 each of the .20 and .28, 2 - .45s, and 2 - .65s. I don't want to bother with diesel heads on the .65 as I don't have any intention of needing a prop that big. A 13x6 APC works well on the .65 on glow for me.

I got my last castor oil order from bulkapothecary.com. $17/gal plus shipping. My old source for castor was SIG until they raised their price from $24/gal plus shipping to $39/gal plus shipping. A bit steep for my blood. S&W fuels sells castor for $25/gal last time I ordered, but Stan kinda ticked me off, so I don't buy from him anymore.