Roto 25
 

I'm thinking about purchasing my first gas engine for a 12 lbs. warbird and currently looking at the Roto 25, RCS 140, and MVVS 160. Does anyone have experience with the Roto 25?

RE: Roto 25
 

Richard,

Just out of curiosity, are you considering a small gas engine for the KMP Hurricane discussed over on the Warbird forum? I am evaluating this now and the RCS 140 looks like a decent choice based upon comments on these forums, but this would be my first gas engine as well.

Travis

RE: Roto 25
 

Actually, I'm considering a small gas engine for a 70" span P-47D Thunderbolt since it has a big cowl. The RCS 140 might be a good candidate for the KMP Hurricane.

RE: Roto 25
 

Which P-47D kit/ARF are you considering?

RE: Roto 25
 

I'm thinking about getting the P-47D ARF from AMD: [link]http://www.amdhobby.com/[/link]

The one pictured in their website is an older version. The new version has black and white checkerboard on the cowl and bubble canopy.

Here is a movie showing the current version: [link]http://www.amd.org.hk/film/p47.WMV[/link]

I was going to put a YS 140 in it, but the YS 140 drinks 20% nitro at around 2.5 oz per minute. Plus, I didn't want to pay $21 for a gallon for YS 20/20 fuel just to get four or five flights. Gas would be much cheaper.

RE: Roto 25
 

That's a nice plane! I know what you are saying about big 4 strokes and the cost of fuel. It's great to see a variety of small gas engine options for that size plane!

RE: Roto 25
 

I might go ahead and order the Roto 25 because I've read some problems associated with the ignition on the RCS 140.

RE: Roto 25
 

As I recall, the YS140 is around 2 lbs, and the Roto25 looks to be around 3 lbs, so the extra weight doesn't look too bad. Do you think you would have had to add weight to the nose of that P-47D with the YS140? The Roto25 has a few favorable comments in RCUniverse and no issues from what I can see, unlike the RCS 140 ignition issue that you pointed out. There isn't a lot of information on it, however. I also searched the Internet and didn't find much. It sounds like you are closer to buying it than me, so I will be curious to hear your comments on this engine if you decide to buy it.

Travis

RE: Roto 25
 

I might need to add some lead to the nose of the P-47 if I go with the YS 140, but I'm not too crazy about the YS fuel consumption rate. The Roto 25 looks very attractive. I found a thread on it:

[link]http://www.rcuniverse.com/forum/m_2089891/anchors_2089891/mpage_1/key_roto/anchor/tm.htm#2089891[/link]

RE: Roto 25
 

Richard, don't give up on glow so fast. My recent experience with a Moki 1.80 was very positive. Use 0% nitro for $10 a gallon. They sip about 1.2 ounces a minute the way I fly and the fuel lasts a long time. I barely used a 3rd of a gallon of Morgan FAI fuel on 5 flights.
Sure gas is still cheaper but add one pound to your plane to go from a Moki 1.80 to a gas engine. And the HP of a Moki 1.80 is about 4 HP peak. Just don't mount the Moki inverted, very hard to start. Just some food for thought.

Joe

RE: Roto 25
 

Joe, thanks for the input. I've heard good things about the Moki 1.80 and 2.10 and several members of my club run them. I was considering the 1.80 for a while. However, on all of my planes (all warbirds), the engine must be mounted inverted, so the Moki might not be ideal. Plus, $10 a gallon is still a lot more than $1.50 a gallon of unleaded gas. It's true that the Roto 25 weighs more than the Moki 1.8. The Roto 25 weighs 3.3 lbs with muffler and ignition. The Moki 1.8 weighs 2.56 lbs (with muffler?), so the Roto 25 is around 12 oz heavier. I'm going to go ahead and give the Roto 25 a shot. The numbers it puts out are pretty impressive.

RE: Roto 25
 

Richard,

I noticed that there is a lot of information about the MVVS 1.60 and many people seem to be using these engines with great success. They seemed to have worked out all the bugs and they are similar in dimensions, weight and power to the Roto25, at a slightly higher cost. The MVVS 1.60 also has a front mounted carb, which I think I would prefer over a rear carb for mounting purposes, i.e., it appears that the Roto25 would have to be mounted with the carb either sticking through the firewall or in front of it. I'll let you know what I decide.

Travis

RE: Roto 25
 

Travis, the MVVS 1.60 sure does look nice. Maybe it will be my next gasser. I just ordered the Roto 25 not too long ago.

RE: Roto 25
 

Wonderful! I am excited to hear how it works out for you. Did you order the plane? Travis

RE: Roto 25
 

Yeah, I got the plane for cheap from the major online auction site. It will be arriving sometimes next week.

RE: Roto 25
 

I kind of thought you'd want it mounted inverted. Better to go with that Roto then. So is it 3.3 lbs including the ignition battery?

RE: Roto 25
 

One thing to remember on the weight comparison of the 2 engines. On the Roto 25 you can run a much smaller tank. You can easily save a 1/2 pound in fuel weight. So takeoff weight is not much different.

Tracy Hill

RE: Roto 25
 

Joe, the 3.3 lbs includes ignition, muffler, and aluminum motor mounts. I don't think the 1400 mAH ignition battery is included.

RE: Roto 25
 

Good point. I believe the Roto 25 is even more stingy on fuel than the Moki 1.80.

RE: Roto 25
 

Richard,

A 7.4V, 1500 mah Kokam LiPo battery with 6V regulator is about 1/3 the weight of Nicads. I've been very happy with this setup.

The LiPo on the left and the 4.8V, 600 mah on the right are about 1/4 oz difference.

Doug

RE: Roto 25
 

Doug, thanks for the info. I have no experience with LiPo battery, so I'm not sure if it's wise for me to use LiPo for my ignition.

RE: Roto 25
 

As long as you charge it outside the plane I'd say it's fine. You certainly won't burn it up on the discharge rate.

RE: Roto 25
 

Hi Guys
I know that this thread is about the Roto 25 but I have been running the 35 in a Eurobat (a 84 inch span 13.5 pound aerobat) Seems to have lots of power, is easy to handle and runs vey smoothly. Although I bought the Roto engine mounts I ended up using the Dubro large antivibration mount and so far seems very sucessful.

Pete

PS How do I add a piccy to a post?

RE: Roto 25
 

I have ordered ROTO 25 yesterday after reading this thread.
Today I came across one of R/C guy of us and I said my ordering of ROTO 25.
He said that I should have chosen twin gas engine, single cylinder gasser has
much vibration compared to twin.
I intend to use my ROTO 25 for 90-120 class 4 stroke warbird, so there was
no way I order a twin gasser since no such small twin is being sold now.
So my question is what do you think of the vibration of a single cylinder gasser?
Is there any mount reinforcement or vibration absorbing mount, the other way
around, needed for a single cylinder gas engine?
He might compare those of so big engines like 50cc or more, though.
I think the vibration level of an gasser is the same as an glow if they have the
same displacement, there is no factor they are different.

Tsutomu Mabuchi

RE: Roto 25
 

many of the small gassers are even smoother than similar sized 4-strokes. no rubber mounts please, mount them hard and make sure the front end of the plane is good and solid.

also don't shy away from lipos for ignition use! they are no more dangerous than any other type of battery, just follow the charge/discharge rules. no need for high $$$ chargers either, this [link=http://shdesigns.org/lionchg.html]simple charger[/link] works great and can be built for a couple of dollars.


dave