Yamaha 160 lb engine. 130 hp

Homebuilt Aircraft & Kit Plane Forum

Help Support Homebuilt Aircraft & Kit Plane Forum:

cblink.007

Well-Known Member
Joined
Jul 7, 2014
Messages
632
Location
Maryland, USA
Seems just putting a Rotax box on the marine version of this engine would be ideal or a modified skytrax.
I have two Apex motors I got for dirt cheap (one running, one not [to use as a training block]); was planning to use a SkyTrax PSRU. I have heard good things about the Rotax C box, since it apparently does not freewheel, but I have been told that I cannot order a new Rotax box on its own, since I do not own a Rotax engine to use it on.

Oh, congrats on your 4000th post!
 

rv7charlie

Well-Known Member
Joined
Nov 17, 2014
Messages
1,564
Location
Jackson
I've never tried to buy a new one, but others have said that there's no issue with ordering one from the distributors.
Search Results | California Power Systems

Search results for: 'Gearbox type c'

On the other hand, IIRC it's a box made for sub-80 HP engines. From what I've read, they've been flown on the 3 cyl Yamahas; don't know about the 4s. But the planes I've read about were very low speed airframes, where the power is likely to be pulled way back after initial climbout.

Jay, my 2nd hand info has been that the sled engine has the internal narrow ratio reduction, which gets shaft rpm down in the manageable range for a PSRU. Supposedly, the watercraft engines don't have that, meaning either lower output, or significantly wider ratio PSRU. Again, 2nd hand info...
 

cblink.007

Well-Known Member
Joined
Jul 7, 2014
Messages
632
Location
Maryland, USA
I've never tried to buy a new one, but others have said that there's no issue with ordering one from the distributors.
Search Results | California Power Systems

Search results for: 'Gearbox type c'

On the other hand, IIRC it's a box made for sub-80 HP engines. From what I've read, they've been flown on the 3 cyl Yamahas; don't know about the 4s. But the planes I've read about were very low speed airframes, where the power is likely to be pulled way back after initial climbout.

Jay, my 2nd hand info has been that the sled engine has the internal narrow ratio reduction, which gets shaft rpm down in the manageable range for a PSRU. Supposedly, the watercraft engines don't have that, meaning either lower output, or significantly wider ratio PSRU. Again, 2nd hand info...
CPS is who I inquired with. They strongly recommended against grafting it to an Apex, and also indicated they were unable to sell me one if I wanted it.

Steve Henry has been pumping 300hp through a SkyTrax without any issues. I know Greg Mills at Mohawk makes a PSRU, but I am having trouble getting metrics from known users.
 

rv7charlie

Well-Known Member
Joined
Nov 17, 2014
Messages
1,564
Location
Jackson
My comments were strictly about using a Rotax C, etc box on a much higher HP engine; not about either of the purpose-built drives for the Yamaha, both of which should be much better suited to the task.
 

cblink.007

Well-Known Member
Joined
Jul 7, 2014
Messages
632
Location
Maryland, USA
My comments were strictly about using a Rotax C, etc box on a much higher HP engine; not about either of the purpose-built drives for the Yamaha, both of which should be much better suited to the task.
All the Yamaha folks using them, I understand, are having good results with the Rotax-C; if I recall, it is the same box grafted onto the BMW R1200GS conversion. I have been told that it absorbs TV really well. I'd love to get my hands on one just to examine it!
 

TFF

Well-Known Member
Joined
Apr 28, 2010
Messages
14,756
Location
Memphis, TN
Rule the one, never discuss your use with anyone when trying to buy. If you want one, just buy. You can’t ask. It’s safer for them to just say no once you show your hand.

Mad scientist has to be all on the buyer. I know it’s an expensive test, but in any of these exchanges, they see you as the Ted Bundy of gearboxs. All they are doing is protecting themselves.

Your engineers have to do the legwork. What if questions is like being in a verbal forum thread. all the seller wants is the credit card number and shipping address. Did you enjoy the Muzak while on hold.
 

cblink.007

Well-Known Member
Joined
Jul 7, 2014
Messages
632
Location
Maryland, USA
Rule the one, never discuss your use with anyone when trying to buy. If you want one, just buy. You can’t ask. It’s safer for them to just say no once you show your hand.

Mad scientist has to be all on the buyer. I know it’s an expensive test, but in any of these exchanges, they see you as the Ted Bundy of gearboxs. All they are doing is protecting themselves.

Your engineers have to do the legwork. What if questions is like being in a verbal forum thread. all the seller wants is the credit card number and shipping address. Did you enjoy the Muzak while on hold.
Agreed, but the chap at CPS specifically asked if I was wanting one for a Yamaha, so I answered accordingly. Maybe they are concerned of the potential bigger impact on their 912/914 sales? They turned down my business, which is their loss. I am okay with that.
 

Jay Kempf

Curmudgeon in Training (CIT)
Lifetime Supporter
Joined
Apr 13, 2009
Messages
4,306
Location
Warren, VT USA
Jay, my 2nd hand info has been that the sled engine has the internal narrow ratio reduction, which gets shaft rpm down in the manageable range for a PSRU. Supposedly, the watercraft engines don't have that, meaning either lower output, or significantly wider ratio PSRU. Again, 2nd hand info...
This is my understanding as well. For my purposes a cog belt drive would work fine. Wouldn't have the TBO of a gear driven oil bath PSRU but it would work. I think C boxes have been taken way past recommendation but that is nothing to bet your life on without a lot of math and testing.

The marine version ends at a LoveJoy jaw type soft coupling without gear reduction. It is more compact and sort of fits the type of cowling that I am looking at. A Lovejoy type coupling could be ideal for PSRU connection. Sorta the same type of torsion damper that is in the rear hub of motorcycles.
 

cblink.007

Well-Known Member
Joined
Jul 7, 2014
Messages
632
Location
Maryland, USA
If you still want the C gearbox, I have one with 3.47 gearing I'll sell. JImChuk 218 seven five zero 38 five one
We were considering it, but after study, we will be doing a SkyTrax box. However, I do have a friend working on a BMW R1200GS conversion and looking for a C box; I'll relay your info to him!
 
Top