Lewis S.

My Feedback: (229)

Hi Guys,
Here are the new mounts for the Thunder Tiger 40 Pro and the OS 40/46 FX and all of them are now up on the web site at WWW.LCSPERFORMANCE.COM

The version that bolts onto the existing backplate come with longer screws. The one that replaces the backplate uses the stock screws. A notch has been milled on the oter edge to clear your throttle push rod.


Lewis

jprge C.

My Feedback: (1)

Hi Louis,
The new mount came today, very nice work. I have one question, will this also work on my Nelson? I appears to be a perfect fit. Also your note with the mount says to use the stock gasket from the engine. If I want to use it on the Nelson what would I do then. Anyway, thanks again, and the notch is a nice touch. I can take the engine on and off the plane now much easier.
Just in case you did not remember which one I orderd, I got this one



Jorge

Lewis S.

My Feedback: (229)

Hi Jorge,
Glad you like the mount. Yes it will work just fine on your Nelson, no problem at all. You can use either an OS or TT-40-46 gasket. I will soon be shipping those with the mounts if people order them for the Nelson. I decided to go that route, instead of an ORing seal. I have never had a convention gasket fail. I which I could find a good source to have a few hundred made.


Lewis

Ed Smith

Just a reminder about rules when using a motor mount that replaces the original backplate. The part of the mount that enters into the crank case must be the exact same size as the original. The volume of the case must not be altered when using this type of mount.

Looking at the photograph of the mount it appears to have a large radius on the corner of the "Boss". The Nelson and the Jett backplates do not have a large radius on the corner. If the depth and diameter of the boss is the same then the rad will alter the volume of the crank case. Therefore I would claim that it's use in a Nelson and Jett is illegal. I cannot speak for other engines.

Ed S

daven

My Feedback: (1)

Ed (Master of AMA rules),

What will the change in volume of the crankcase do to the performance of the engine?

Just curious, not questioning the rule or legality of the backplate mount.

Lewis S.

My Feedback: (229)

Hi Ed,
That is a very valid point. The whole reason I put a small radius on the corner was to prevent nicking if you ever happen to drop in on the ground or off your workbench. As to the same volume, I guess there would be some question as to what tolerance was held during manufacturing. I just did a volume calculation and the difference is .108 % less volume than my Nelson that is 2 years old. I compared it to a brand new one and the number is .102 % essentially the same number.

As to the change in volume having a performance effect, we just tried both mounts with no rpm change detected. Just trying to make a better mouse trap. Any idea who could tell me yes or no on if they were legal? The program would take 5 minutes to change the radius.

Thanks for the input,
Lewis

Ed Smith

The popular wisdom is that the more the crank case can be filled (Lesser volume) the better the pumping action of the descending piston. In some older engines the crankshaft counterbalance was slotted to achieve some sort of balance and then an aluminum band was sweated on to the flange. It appeared as if there was no balancing of the crankshaft as all that was seen was a full disc. Underneath the band was a deep slot cut into the flange.

In order to prevent any type of modification in this area the rule was written as it is. It is illegal to increase or decrease the crank case volume. The outside of the mount can be any configuration but the inside must match the original.

Ed S

Lewis S.

My Feedback: (229)

Hi Ed,
Thanks again, I understand the idea of stuffing the bottom end, I have worked on engines for years, and you are 100% correct. In theory the better you pack the bottom ,the better the top end delivery. To be honest, I have talked to some of the best speed engine builders over the years, and they all say it is supposed to, but none of them know for sure. George Aldrich said he always thought it was a bunch of *&^$ since he said as far as he knows a detailed study on internal engine dynamics for our stuff has never deen done. Who knows for sure ........

Again thank you very much, a rule is a rule, and it is in place for a good reason. I have to find out what the tolerance is on "same volume"

Lewis

basmntdweller

My Feedback: (9)

I don't know who it was, but a speed flyer some time ago made a variable volume backplate. His findings were that volume made little difference till the case got rather large, as in a flat backplate. His thoughts were that the open area gave a freer flow path to the ports negating the gains from increased pumping action.
It's amazing I can recall something I read from the late seventies or early eighties but can't remember what I was doing ten minutes ago!
I'd almost bet even money it was Glenn Lee that wrote it.
Later,,,basmntdweller

Ed Smith

I doubt very much if anybody will commit to a "Volume tolerance" As you stated before it takes only a few minutes to change the program. So reproduce the original then there is no issue.

Ed S

Lewis S.

My Feedback: (229)

Hi Ed,
Program is fixed so it is no longer an issue. Now all i need is a good source for gaskets. Does anyone have a Tiger Shark 40 or 46 out there?

Lewis

PylonWorld

Lewis,

I have some Tiger Shark .40's ... they are not the same size backplate as the OS 40/46, TT Pro 40/46, Nelson, or JETT.

Supposedly they have been revised, but I was told they are minor revisions (no red anodized head). A backplate or gasket for the TS will not fit the above engines unless they made bigger revisions than I was told.

We've been running them on the Vipers with good results. The ones I have are true ABC engines.

Per_N

Lewis
Looks like you redesign my backplate for Webra to TT. In that case I'm pleased that it came out useful.

Regards
Per Nordengrim

Per_N

Daven
I have'nt find any difference in performance. But I guess there would be some discussion if this is legal or not. Over here it was not so popular when I came with it. So I redesign it to still use the original backplate. It could be downloaded from my site.

Regards
Per

Per_N

How it looks mounted.

Stand

Per-N,
Is that a fillet I see on the fuse at the wing?

[8D]
Stan D.

daven

My Feedback: (1)

I was going to mention the same thing about the fillets Stan, the mount looks great Per. Our only issue, is that the we use the O.S. .46 fx, which has the rear needle attached to the backplate. Ours rules don't allow non-O.S. needles to be used, so if you replace the backplate, you have to remount the original needle somewhere. This makes it almost nessecary to use some sort of backplate that mounts to the original backplate like Lewis's. The square one is good, but you have to grind a way the metal that holds the needle to get at the bolt that goes into the firewall. You can use the round one, but then you have a different bolt pattern than the Nelson backplate mounts. Its nice to be able to fly either engine on the same plane.

Lewis S.

My Feedback: (229)

Hi Per,
Actually I made these mounts for the K&B 4011 engine the last 8 years for the guys in NEPRO and just changed the bolt spacing to handle the Thunder Tiger 40 Pro.

Lewis

Lewis S.

My Feedback: (229)

Hi Dave,
Problem is solved, I will have my new mounts ready for the OS 40-46FX ready in a few weeks. You will not have to modify the engine or the mount to use them. I made the first one today, I just have to order more aluminum.

Lewis

Per_N

Yes Stan there is a fillet.
In our Quicke class there is only 2 models allowed. They are Sonic 500 and one that is made in this country, called "Ryggskott" a little bigger fuselage but thinner wing profile. And the Sonic has fillets original so thats ok here.

Per_N

I post a pic of my sonic, But the other model "Ryggskott" we have here in Sweden is the one at my avatar.
Just so there is no confusion.