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Displacement check for the TT Pro 40

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Displacement check for the TT Pro 40

Old 07-22-2012, 03:12 PM
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Default Displacement check for the TT Pro 40

Here isa way you can check the displacement of your Thunder Tiger Pro 40 engine.

I used a Harbor Freight Digital Caliper to do these measurements. It only cost $14.99 and gets the job done. If yours feels a little gritty when using it, wash it down with some WD-40 and you will see a bunch of black crud come out of it. Work it by extending it and colapsing it several times to work the black crud out.

Step 1: Remove the engine head

Step 2: Measure the bore (see picture #1) Should be 20.9mm or .823 Less is okay more is not!

Step 3: Extend the caliper about one inch and slowly push the piston down with the caliper rod until the caliper rest on the piston liner (See the picture #2).Carefully Reset the ZERO. This is Bottom Dead Center (BDC)

Step 4: With the caliper back in place as step 3, rotate the prop until the piston reaches the top of its stroke and starts to go back down (see picture 3). The piston will have stopped pushing the caliperonce Top Dead Center (TDC) has been reached. This is your measurement of the stroke. It should be 19mm or .748. Less is okay but more is NOT!

This was edited to show a simpler way of doing the measurements. Thanks Jim McGuinn!
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Old 07-26-2012, 07:43 AM
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Default RE: Displacement check for the TT Pro 40

Tim, if you reset the caliper to zero when at bottom dead center and then rotate the prop all the way up it will give you the stroke in a negative number. This is faster and you don't have to do the math.
Old 07-26-2012, 10:41 AM
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Default RE: Displacement check for the TT Pro 40

True and a good idea. I was shooting pictures of this and needed a third hand........
Old 07-26-2012, 03:54 PM
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Default RE: Displacement check for the TT Pro 40

Tbatt, thanks for the post on “how to”. But I’m afraid some may not do this simple step before the race. To help in the preflight inspection it may be a good idea to ask the pilot if they checked the displacement of the engine. If the answer is yes, well and good, but if NO, then the pilot must be advised that if final inspection shows the engine to be illegal he will be disqualified.

With all the hype on this problem, I cannot believe that those involved in Club 40 are not aware of it; but there are those 10%.

Just my thoughts on the issue.
Bob
Old 07-26-2012, 08:07 PM
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Default RE: Displacement check for the TT Pro 40

I just measured one of my new engines. Ive had it new in the box for about a year or so until I fired it up about a week ago.
Here is what I got with my meaurements ; I have an analog caliper as well as a digital like Tim's and between the two measuring devices there was about a .002 difference, no big deal there....
bore was .812 and stroke was .753 .
John
Old 07-27-2012, 04:28 AM
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Default RE: Displacement check for the TT Pro 40

John, that’s close enough for the Chinese QC. That makes it a .389940****, or about a 40. Using the numbers shown in their booklet, the displacement would be .397916****. In any case these numbers are acceptable and a long way from .456 cu.in displacement of the TT-46.

Bob
Old 07-27-2012, 04:56 AM
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Default RE: Displacement check for the TT Pro 40

Bob,

I think that Dave Philips is planning on tearing down all of theengines that race in the A-C Main races. Rick Grim will be doing the pre-race engine inspection.

Dave?

Tim
Old 07-29-2012, 07:57 AM
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Default RE: Displacement check for the TT Pro 40

Tim, that’s great. I’ll have my dial caliper and depth gauge with me if he needs help.

Bob
Old 07-30-2012, 08:15 PM
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Default RE: Displacement check for the TT Pro 40

I just checked my second engine, I measure .810 bore and .756 stroke, so I guess Im good to go. They may find some other reason to dq me, but it wont be for having a larger displacement engine !!
Old 08-01-2012, 05:02 PM
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Default RE: Displacement check for the TT Pro 40

Sounds like you know something John !! If we find it

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