[I just received a Tower's .75 abc engine. For the money it looks really good ($95.00 U>S&gt Just for the fun of it I am going to stick it in a G.P. Easy Sport ARF. I never seem to have enough 'vertical"!! First, does anyone know what this engine is - really. From mag. pics it looks similar to a GMS. Also, do you think the Easy Sport will fly ok with the .75? I also mentioned this as a topic in the ARF forum.

Pappy S.

Yes your plane will fly fine with the Tower 75. I've been around a Easy Sport 40 with a Super Tigre 75 for some years. It was plenty hot but everything else was fine.

Yes, the engine is made by whoever makes GMS. It is a ABC engine but the GMS is ringed.

Jim

I had an Easy Sport ARF with an OS .61SF in it. It was a little nose heavy, but flew well. The engine mount will just spread enough to mount the engine. I added anhedral to the wings so it would knife edge better. You might want to build the plane first with the engine, then see if you need a servo or two in the rear for balance.

I would also run a threaded rod between the cheeks below the engine crankshaft. We had several of these planes in the club at one time and a common malady was the cheeks vibrating, causing the firewall to come loose. Some type of rod or dowel between them stops the vibration. As I said, I used threaded rod with 4 nuts, inside & outside of the cheeks.

I also changed out all the control surfaces. I added 2" ailerons, 3" elevators and a 4" rudder. The stock surfaces are fairly small, as befits a semi-trainer.

I think I also changed the gear out for a longer one and a longer nose gear.

I ran an APC 12-7 prop, but for a .75, a 12-8 might be better. You'll have loads of vertical.

Check my web site for anhedral planes and the Droopy Project for pictures of my Easy Sport.

Two Thumbs up for the Tower .75 ! I've been running one in a GP Shoestring, mounted horizontal with an APC 12x8, Bisson muffler. Engine fits inside the cowl without cutting it, and does not overheat on 15% nitro. The .75 has been rock solid, transitions great and even shuts off when I ask it to. Pulls the 8 pound Shoe around well, radared at 106 a number of times. If you get one of these, just give it a correct break-in
like the mfr. describes ,seal the carb to the case with RTV , and you will be rewarded with a very reliable and powerfull unit.

Sounds like the Tower .75 may have been a good investment. I hope mine works as well as your's Joe. So the carb needs to be seals to the crankcase. What is RTV, a specific brand name or generic description of some type of sealant or bonding agent? Can it be easily removed if neccessary?

Terry (Pappy S)

Terry,


Using a prop with a larger disk area (diameter) will give you the best vertical performance.

It will come at the cost of a little less maximum speed.

The sizes I would recommend are 12.5x6 (Bolly or APC) and 13x6 (APC).
The RPM would be higher (more HP) with the 12.5x6 size.

Terry, RTV is a high temp silicone gasket maker. I use the Permatex brand which is orange in color. Stays semi flexible but bonds well and is fuel proof. Works well on all muffler joints also. Be sure to clean all mating surfaces with alcohol, and run a bead around the joint on one surface, bolt the pieces together lightly, let the sealant set up overnight, then tighten the parts down, and trim any excess off. The trick to this stuff is to not tighten the parts until it sets up or you will sqeeze it all out. Hope this helps.

Thx Joe; I will definitey look for the Permatex brand. I am assuming one doesn't use the o-ring that comes with the carb if the sealant is used - correct? Do you know if there has been a problem using this engine with just the o-ring under the carb?

Terry (Pappy S.)

It's based on an older Super Tigre series & is a very close cousin to the GMS 76 engine. In this case the GMS .76 is a ringed version & the Tower .75 is the ABC varient. The advantage of the GMS, aside from the ring, is that it is available with a front needle valve & seems to have fewer quality prolems.

Terry, I use the o-ring, and then apply RTV as a backup. I do this on all my new engines to prevent any air leaks at the carb to crankcase, which seems to be a common problem. If there is an air-leak at this point or at the backplate, the engine will not adjust properly or shut down when the throttle is fully closed.

Britbrat, the Tower is supplied with both a front or rear needle valve option. I prefer the front NV setup too. As far as the ringed GMS versus the Tower, I've dealt with both of them and think the Tower has a much better carb, which offsets the higher cost of rebuilding the non-ringed Tower when the time comes. Both seem to put out about the same power.

Terry.

I've been running a Tower 75 exactly as it came out of the box. Haven't added any sealant of any kind anywhere on the engine, and it runs fantastically. Break it in slowly (take your time, that is), and you will enjoy a fantastic, inexpensive engine.

Misterpanda

I am planning on building a 65" warbird and was trying to decide between the tower .75 and the gms .76. It sound like both engines offer about the same power and are both reliable from what people are saying. I own both gms and tower .46 engines and have been happy with both. So I guess my question is which is better abc or ringed style engines?

When you have to rebuild a ringed engine do you only have to replace the ring or is it also necessary to chance the cylinder sleeve? I heard that the break in period for a ringed engine is more difficult and that they are more easily damaged from running to lean. Anyways would like to tap into some experience here.