HP 61 for stunt?

[Andrew Tinsley]

Hello everyone,

 Have just been given an HP 61. It is a ringed engine that appears to be Schneurle ported, with a flat top piston. It is a very well made product and this engine is in excellent condition.
  Does anyone have any experience with this motor for stunt? It is a little on the heavyside, but I have a model that could do with some nose weight! For the first time in years, I have managed to build a model that is not tail heavy!
  I realise that I will probably have to go the low pitch / higher rev approach and I don't mind tinkering, if anyone can suggest a ball park starting point. The plane is purely for sport with no serious pretentions at competition. I was going to install a Merco 61, but is the HP 61 worth a try instead?

Thanks,

Andrew.

[Steve Helmick]

Long-ish crankshaft, rear drum induction? Well, why not give it a try? A venturi with about .300" bore with a .156" ST type spraybar through it would be about right, with around 4" pitch props. You could also block the boost port and see how that works with 5"-6" pitch. That, or sell it on eBay and buy a Rustler .61 Metamorph?  Steve

[Andrew Tinsley]

Hi Steve,
              This HP 61 is a FRV model and the cranckshaft appears to be of normal length. Don't think that it is particularly rare or desirable, so it is unlikely to fetch anywhere near the price of a Rustler Metamorph! Anyway, I need some serious nose weight and the Rustler is not exactly a heavyweight!

Andrew.

[Bill Morell]

Is this the HP 61 that has the black case and gold head?  If so you can look it up on Mecoa's website. They still build them for R/C and for U/C stunt. Not exactly cheap either.

[Steve Helmick]

Well, you might still try blocking the boost port...or trade it for a .65LA?  Steve

[Andrew Tinsley]

Hi Steve,
             OK I will get the JB weld out and give it a try! Guessing that something like a 13 x 4 may be a good starting place for a prop and maybe around 10,000 rpm launch revs? Bill, I think that you are correct about the model. I believe that the engine you describe is the Gold Cup model. The one that I have is the plain finished version. I know that HP stopped making engines and concentrated on their arms business. I thought that Mecoa had the rights to the engines, but didn't know that they actually manufactured them! Maybe a query to Mecoa might give me the required info, especially if they do a U/C version!

Andrew.

P.S. sorry about the previous typos. I can spell ....... honest!