EQ1

Well, looks like there are some things going on at UMS. I had contact to them and they are not selling their engines through Horizon since some time. In Germany the distributor is Tomahawk Aviation https://tomahawk-aviation.com/ . Hopefully the service will be better, HH was terrible. Needed to buy the spares directly from UMS, fortunately they were very helpful.

Concerning the engine re-design: apart from the new color sceme with black cylinder heads I am not sure whether the pictures really represent the actual engine. The 7-35 that Lars linked above looks like the 7-77 and their new 115 9 cylinder gaser looks exactly like the 9-99 glow engine. Maybe their marketing department is a little behind.

Nevertheless: I really appreciate that they are still present on the market and hope that they will stay.

Fulcrum2111

Two short videos of my 7-35

Maxam

My Feedback: (62)

You will notice the heads are no longer screwed on, rather there are now 4 or 5 head bolts. UMS started to have real trouble with leakage between the cylinder and the head, especially with the 160 gas. -Tom

CannonFodder

My Feedback: (23)

Hi Tom,

Have you or do you know of anyone who has purchased one of the new gas radial engines the 50 90 and 115 CC. Very curious to see one run and how they sound.

Thanks Mark

EQ1

Tom, could you please explain, why bolts rather than screws will be better with repect to leakage? As an engineer I would say that the pressure between the connected parts, put on to the gasket, will seal everything. And the pressure will be the same using bolts or screws, just depending on the torque on the screws/nuts. Thanks for any further insight.

Maxam

My Feedback: (62)

Cannon Fodder and EQ1, I have not seen except for pictures, any of these engines, nor have I talked to anyone who has them. They sent me a gas engine to evaluate and it did not go well. I think UMS was put off with my candid responses. Threaded heads onto cylinders is a high precision process that requires top notch machining. Personally all my engines had no issues but I had acquaintances that had great trouble especially with the 160 gas. -Tom

Maxam

My Feedback: (62)

Fulcrum 2111. Liked your video! -Tom

CannonFodder

My Feedback: (23)

Hi Tom,

Thanks for the reply on the new UMS engines. BTW I found myself an unbuilt Curtiss Robin (RobinHood model) like yours. I will be putting my 7-77 on it since the engine was not enough power to pull a 32 lbs 1/5
AT-6. Now I need to find time to build the Robin, by chance did you make a 2 piece or 1 piece?

Maxam

My Feedback: (62)

Is yours the Robin Hood 99 or the 80? The 7-77 would be perfect on the 99. Mine has a one piece wing. ....and I have the 9-90 on it. The 7-77 would be better but It is what I had at the time. -Tom

CannonFodder

My Feedback: (23)

It is the Robin Hood 99, I am going to try and be as scale as my skill allows. Modeling a late version, plus making a 2 piece wing. Got to get the radial in the air!!!

Mark

David Johnston

Hello radial fans!

I read that some are having troubles with air and/or fuel leaks on their radials. Here is a photo of my never used Evo 7-35.

Is it necessary to add O-rings under the jam nuts on the fuel intake tubes? Also, is it necessary to add something like Permatex RTV high-temp silicone to the crankcase backplate?

Thank you for any suggestions!

–DJ

Maxam

My Feedback: (62)

O rings should already be installed on the intake tubes. Someone else got a 7-77 and it did not have O rings. Obviously the guy was not happy! A very thin layer of RTV or gasket seal would be fine. -Tom

David Johnston

Good advice - thank you Tom!

--DJ

Fulcrum2111

thanks for your words, Maxam
I used teflon tape to seal the exhaust ports to the exhaust ring Instead of the supplied washers and I have no leaks and also acts like a threadlocker.
regards

David Johnston

Hello Fulcrum - Teflon is probably an even better idea because I won't have to search for the correct O-rings.

Thanks!
--DJ

barzini

My Feedback: (4)

Hello everyone,
I would like to break in my 7-77 radial according to the Evolution manual.They recommend methanol and oil no nitro necessary.What oil should I get to mix with the methanol?
Thanks,T.C.

Maxam

My Feedback: (62)

Barzini, After running these engines all these years just dilute regular 15% nitro fuel 20% oil 1 to 2. I now never run these engines with no less than 10% oil. The cam track will wear with less oil and the nitro makes these engines run much better. Pay great attention to a thorough anti corrosion oiling after running. Refer to my extensive discussion elsewhere in this thread. I wrote those directions for horizon and since went to higher oil content. -Tom

GIJon

My Feedback: (118)

Hello to all and thank you for all the R&D on these engines. Especially you Tom for starting this thread and staying with it for so long.
So...I purchased a Wild Hare 90" Grumman Hellcat from Tom Fawcett when he was selling them. I purchsed a RTC from him and decided at that time I would like to power it with my Saito 450 radial. Fast forward to 2014 I decided the EVO 777 was the one I would want for the Hellcat, so I sold my 450 and added some $$ to purchase my EVO 777 from Advantage Hobby in July 2014. Then I got involved in a cross-country move. The engine sat in storage for almost 2 years and last year, I built my new home and shop. So basically, the engine has been sitting in the original box for 3 1/2 years.
While at Joe Nall last May, I had a nice conversation with Adrian at CH-Ignitions. He had some interesting information. We talked about outfitting this radial with CDI/glow. I have run glow engines on CDI before and they are sweet. He also mentioned that there are 2 ring groves in the piston and adding a second set of rings would increase power.
So today, I ran across this thread again and started reading. It seams I could save a significant amount of money by running without onboard glow or CDI and invest in the OS 46481000 Carburetor and Adrian's adaptor so tuning will be more precise.
I have made plenty of notes from the thread and will follow the advice on fuel mix, corrosion prevention, and prop sizes, etc.
Now for the final note...over the last year, I have removed the radial from the box to admire it with friends, but have not done anything else with it. Today I took a break from reading and decided to check out my beautiful engine once again. Well, it would not turn over. It was frozen solid as a rock. I removed all of the glow plugs, squirted in some Marvel air tool oil in each cylinder. I also removed one of the pushrods and put air tool oil in the crankcase. Using a rocking motion, the engine started to free up. I then removed the back plate and squirted a fair amount of air tool oil on the front bearings, connecting rods and everywhere else I could. Inspection of the interior of the engine showed clean. No evidence of rust or corrosion. The old oil they put in it from the factory was pretty stiff. I even used my heat gun to warm um the crankcase a bit to free up some of that. It turned over pretty nice and I buttoned it back up and replaced the glow plugs and turned it over several more times and put it back in the box.
It has been too cold here for too long and trying to test run it is totally out of the question for now.
I know this is a lot to digest, but any thoughts of what I have covered is much appreciated.
Jon

GIJon

My Feedback: (118)

I also found Blue Block is no longer available. Any suitable replacements

Maxam

My Feedback: (62)

I use Marvel air tool oil or any other air tool oil and you will be fine. Sounds like you are using common sense and yes the OS carb is a great improvement. The CH adapter is marginal due to the holes for the carb are off. You will need a tiny rat tail file to widen the holes.....or seek someone with a good lathe. -Tom

tdevince

It looks like Horizon Hobby's line of Evolution engines are declining. The only radials they have on their website are the 7-35 and 7-77, all others show discontinued. I know UMS still makes and sells these engines. Is UMS still selling to Evolution and Horizon is no longer carrying the Evolution radial line? If so, is there another supplier for Evolution Engines? If Evolution is no longer carrying these engines, is there another source for the UMS engines in the US?

GIJon

My Feedback: (118)

Just ordered a set of rings for my 7-77 from UMS Technologies. Wow...very pleasant people to deal with and great customer service.

tdevince

Good to hear, are they shipping direct from India? Do you know what the expected delivery time is from India?

CannonFodder

My Feedback: (23)

Hi GIJon,

Did you order these to add the second set of rings or replace the current ones?

Thanks, Mark

barzini

My Feedback: (4)

Did anyone put two rings on each piston?
I was wondering how the engine would perform.