Envelope-to: craig@dapaero.com
Delivery-date: Sun, 14 Aug 2022 09:19:44 -0500
Message-ID: <7742a11d-5e8f-86fd-f820-ccf0bfc13a8b@nctv.com>
Date: Sun, 14 Aug 2022 07:19:30 -0700
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Subject: Re: hand car
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To: DAP AERO <craig@dapaero.com>
References: <2c1aa060-0663-76a3-f416-2b5f23f389e4@nctv.com>
 <21F97698-0560-49C8-A879-CC56C09D360E@dapaero.com>
From: Curtis Andrews <andrewscc@nctv.com>
In-Reply-To: <21F97698-0560-49C8-A879-CC56C09D360E@dapaero.com>
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One has to ask why did they not just put the connecting rod vertical on 
the other side of the rocker arm like a car piston. Running mine that 
way was easy and it ran smooth.   But to make it look right, and 
thinking there was some kind of mechanical advantage to run the 
connecting rod to the other side of the rocker arm, I physically 
searched for where to pin it to make uniform motion at the maximum 
stroke and minimum stroke of the rocker arm (due to  physical constrains 
of the rocker arm.  it was deceivingly complex with few solutions with 
the four variables but when done,   I was determining the length of 
connecting rod, when i found the 38" coincidence to the rocker arm pivot 
point. (measuring as close as i could around stuff in the way, so will 
be curious if it is true in your drawing).

On 8/13/22 9:29 pm, DAP AERO wrote:
> no. I never would have seen that. And I don’t see why it is the solution
>
>> On Aug 13, 2022, at 7:01 PM, Curtis Andrews <andrewscc@nctv.com> wrote:
>>
>> ﻿i either figured it out or found a strange coincidence
>>
>> When the crank and connecting rod pivot are not symmetrical there are only  a few connection points that will make the rocker arm motion equal above and below center, and equal motion on both side of the rocker pivot.
>>
>> Our distance from the center of the crank to the center of the rocker arm pivot point is 38" .  using the center of the crank for the center of a circle, draw a 38" radius arc from the rocker pivot.
>>
>> With the rocker arm horizontal, then the connecting rod must be pinned on that line.  hence the offset.  anyplace else and the motion will not be uniform.
>>
>> for our configuration, the three offsets that i used are 8 5/8 Horizontal from rocker pivot shaft,  and 2 1/4 vertical below center of rocker arm. Producing 27" stroke at both handles.
>>
>> 11 1/8 horizontal and 3 3/8 " vertical,  for 21" stroke
>>
>> 13 5/8" Horizontal and 4 1/2" vertical.   for 17" stroke
>>
>>
>>
>>> On 8/12/22 11:12 pm, DAP AERO wrote:
>>> I spent days looking at modeling and could not figure it out. I don’t think it is trivial. I couldn’t even finish the equation that gives the position of the pump end of the push rod as a function of the drive gear position.
>>>
>>> This last video has the maximum torque point which I think is when the push tod id tangent to the drive gear. But that may not be correct.
>>>
>>> Not sure when I will drive up next, how many windows are there?
>>>
>>>>> On Aug 12, 2022, at 6:35 PM, Curtis Andrews <andrewscc@nctv.com> wrote:
>>>> ﻿For something so simple, i spent hours today and can't figure it out.
>>>>
>>>> i have noticed my mental abilities are deteriorating and this is a test of how bad.
>>>>
>>>> Oddly, my initial offset which was placed based on the size of a scrap piece of steel and where it had existing holes seems to be amazingly close.  the connection simply does not work in many other places, one end of the stroke or the other is off.
>>>>
>>>> Now i am thinking of making the stroke adjustable on the rocker arm so on a down hill movement it moves 21" and uphill it moves 27"   With 24" being the flat track middle stroke.
>>>>
>>>> Have never seen any original ones with adjustable pivot point, so don't know how useful it will be.  But to do that with the same length arm,   has the offset about 2.5 down at 8.5" from center, and 4.5" down at 12" from center.  I will built a test tomorrow to see if it works.
>>>>
>>>> When are you planning on driving up this way to bring glass?
>>>>
>>>> -- 
>>>> Thank You
>>>>
>>>> Curtis Andrews
>>>> 1336 E Oak St
>>>> Othello WA. 99344
>>>> andrewscc@aol.com
>>>> 509 346 8108
>>>>
>> -- 
>> Thank You
>>
>> Curtis Andrews
>> 1336 E Oak St
>> Othello WA. 99344
>> andrewscc@aol.com
>> 509 346 8108
>>
-- 
Thank You

Curtis Andrews
1336 E Oak St
Othello WA. 99344
andrewscc@aol.com
509 346 8108