I wasn't old enough to be a user of these engines when they first came out so my experiences are only from the last 15 - 20 years since my return to c/l and dabbling with vintage A team race models.
My Frog was used in the first vintage A racer I build back in the early 90's. It was a Footprint and I still have it. When I built it I even included the angled forward kinks in the u/c wire but later removed them to simplify the landing gear. It even had the ridgey didge flat bottom "Clark Y" section !
Anyway I digress.
I think it's only when you push the Frogs really hard that this case weakness becomes a problem.
According to Ivor F, he related a tale of one of the importers of the time having a load of returned engines in a drawer all with the same problem.............broken cases and in many examples the case was in 2 parts, all breaking around the rear bearing housing area.
Now I know I was giving my engine a hard time. It was in a racing model. I do believe however that there is some substance to this type of failure with the earlier models.
I would advise conservative settings to avoid heart break, you don't see too many brand new Frog 2.49 BB crankcases floating around looking for new homes
I don't think there is adequate meat around the front bearing.
To this end I have bought new bearings of smaller OD and was going to make a one piece sleeve of steel to tie effectively beef up this area and tie the front of the case to the rear of the case.
Easier to draw than to explain. It's pretty low on the list of to dos out in the workshop, but I have the R110 bearings and will get around to it at some time.
Stan Pilgrim, a very well known and highly respected Australian engine tuner with a long list of success's was of the opinion that the earlier version Frog 2.49 could be made to go very quickly if one wanted to. I think he may even used one in the earlier years of vintage A.
There is no doubt though the Oliver is a far superior and much more robust design much better suited to the rigors of racing.
Here's a pic of the Footprint with the Frog 2.49 BB.
All the wing damage was done when loaned to a friend
