Path: ...!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!eternal-september.org!.POSTED!not-for-mail From: AMuzi Newsgroups: rec.bicycles.tech Subject: Re: Suspension losses Date: Sun, 5 Jan 2025 09:57:46 -0600 Organization: Yellow Jersey, Ltd. Lines: 83 Message-ID: References: <40fjnjt0shr6em0c38du1nebppfl6l6aej@4ax.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Injection-Date: Sun, 05 Jan 2025 16:57:50 +0100 (CET) Injection-Info: dont-email.me; posting-host="b5bb20b03f11395a0d011036ed2b3e7b"; logging-data="1156666"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX1+Ch+bIzORviD3T1OkmdS2d" User-Agent: Mozilla Thunderbird Cancel-Lock: sha1:c0J0EyFPCZtD0kEzoCzSvWdTq/M= Content-Language: en-US In-Reply-To: <40fjnjt0shr6em0c38du1nebppfl6l6aej@4ax.com> Bytes: 5328 On 1/4/2025 5:20 PM, Jeff Liebermann wrote: > On Sat, 4 Jan 2025 16:28:21 -0500, Frank Krygowski > wrote: > >> On 1/4/2025 2:52 PM, AMuzi wrote: >>> On 1/4/2025 1:36 PM, Jeff Liebermann wrote: >>>> On Sat, 4 Jan 2025 12:35:20 -0600, AMuzi wrote: >>>> >>>> User manual on an early analog computer including a few useful >>>> examples.  Try to visualize what those problems might look like on a >>>> slide rule or today's personal computers: >>>> >>>> >>> >>> Ah, such as a slide rule. Got it, thanks. >> >> The device I was talking about was nothing like a slide rule. > > I called the analog computer that I build in a briefcase an > "electronic slide rule". I didn't want to, but that made it more > acceptable to the college bureaucracy. > >> It looked >> vaguely like the one in Jeff's last link above, but the classroom >> demonstrator was much larger - maybe 3' x 4' IIRC - with much bigger >> knobs (4" diameter?) and meters. > > I couldn't find anything with such huge knobs. Maybe something like > these from Edmund Scientific? > > > Would you believe a Heathkit EC-1 analog computer? > > > Fig 7 is a bouncing ball simulation, which is similar to the bouncing > bicycle simulation. > >> We were talking about electrical analogies for vibrating masses, and >> that's one of the things the analog computer could simulate. One would >> have to calculate the values of voltage, inductance and resistance to >> correctly simulate the damped spring-mass system, set initial >> conditions, then let the circuit run. The system's meters would then >> swing back and forth in a manner analogous to the position of the mass. >> All this was before digital computers were desktop devices. > > Meters? Too crude. We used an oscilloscope or X-Y pen plotter. > >> (In those days, the programs I wrote for vaguely similar problems were >> room sized and run by full time technicians, and I'd turn in a program >> stored as a thick deck of punched cards, hoping output would be ready >> the next day.) >> >> As I recall, we students never did any actual work with that analog >> computer. > > We did. My guess(tm) that would 1969. We had groups of 5 or 6 > students sharing one machine. I got some extra experience because I > worked for the "calibration department" repairing them. The problem > was we had a large number of foreign exchange students from Iraq. Most > had never done any manual labor or learned to use tools. When faced > with a knob that had reached its end of rotation, they simply applied > more force to help it rotate. That usually broke the expensive 10 > turn potentiometer (Helipot). > > > I was the idiot who found a solution to the broken potentiometer > problem. Between the knob/turn_counter and the pot was a short shaft > extension. I machined a few of these and added a plastic shear pin. > If they hit the end of rotation and break the pin, all they had to do > was rotate everything full counter clockwise, push the pin out of the > hole, and replace it with a new pin (or toothpick). The reason I was > an idiot was because I had found the solution, I sentence to working > overtime retrofitting all the analog computers with shear pins. > Thank you, especially for the Heath Kit page (although much of that went beyond my understanding). The reader comments were great, especially the last one! -- Andrew Muzi am@yellowjersey.org Open every day since 1 April, 1971