Audio recording of my CF's chain drive

Do you own or run a Bedford CF Electric then this is the place for you to discuss it here.
Griffon
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Audio recording of my CF's chain drive

Postby Griffon » Fri Apr 03, 2009 4:32 pm

Ok folks -- here it is. An MP3 file containing a recording made by placing a small microphone just behind the chain drive case of my CF Electric and going for a drive.

http://www.frontiernet.net/~jfletcher/griffon.mp3

Total running time is about 16 minutes. Here's a reference list of what the van was doing at particular times during the drive:

00:00 Leaving parking spot at house, driving up steep driveway to street level
00:40 Clearing the top of driveway, accelerating down side street
00:58 Right turn onto another side street
01:32 Come to dead stop, then right turn onto main street, accelerating to about 25 mph on level grade
02:30 Start descending gradual downhill grade
~03:10 Start climbing uphill grade
~03:30 Start descending long downhill grade
05:05 Right turn at stop sign, then accelerate to about 25 mph on level grade.
06:50 Climb short, steep hill to highway intersection.
07:14 Come to dead stop at highway intersection, wait for traffic to clear, then left turn onto highway, accelerate to about 45 mph (highway is basically level grade)
09:40 Slow down and turn into gravel turn-around area, wait for traffic to clear
10:11 Turn back onto highway, now going back opposite direction. Accelerate to 45 mph.
12:45 Slow down and make right turn from highway onto side street, then accelerate to about 20 mph going up gradual hill
13:40 Stop sign, then left turn onto main street and ascend gradual hill, then level grade at about 25 mph
14:47 Left turn onto side street leading to my house
15:18 Enter driveway slowly, proceed down steep hill to level area at house
15:50 Reverse into parking spot


I'd appreciate if someone familiar with these CFs (Chris? John?) could at listen to at least a few minutes of this recording and let me know if you think this sounds reasonably normal (can't expect perfect on a 25 year old van). I have no experience with a "known good" CF Electric drive system... it sounds to me like this one makes a lot of noise, but maybe they always sounded like this?

If you like technical details, the mic was a Shure SM11, recorder was a Nagra IV-L (full track) running 7.5 ips (unknown type of tape, whatever was on that 5" reel). I used the automatic recording level control on the Nagra. Recording was digitized using an M-Audio Audiophile 2496 sound card, saved to a 44.1k/16 bit mono .wav file, then encoded to MP3 using LAME.

- John

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Flying John
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Postby Flying John » Tue May 12, 2009 2:15 pm

Typical sounds coming from it I think except the (what sounds like) chain chatter.

I would adjust the chain tensioner. I am just trying to remember whether you can do it from the rear of the casing without dropping the motor. I think you can - Looking at my motor and gearbox I have here it can be done but I cannot remember what clearance you need out the back to take off the cover.

John

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ChrisB
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Re: Audio recording of my CF's chain drive

Postby ChrisB » Tue May 12, 2009 9:07 pm

Yep, as with John all sounds fine and dandy apart from the slight chain rattle, check the oil level in the transfer case, and as John says would pay to tighten the chain a bit.
Do remember the controller runs a very low frequencey and thus is quite noisey, for us here in the UK it sounds like a standard milk float 8)

Griffon wrote:
If you like technical details, the mic was a Shure SM11, recorder was a Nagra IV-L (full track) running 7.5 ips (unknown type of tape, whatever was on that 5" reel). I used the automatic recording level control on the Nagra. Recording was digitized using an M-Audio Audiophile 2496 sound card, saved to a 44.1k/16 bit mono .wav file, then encoded to MP3 using LAME.

- John


Image

Lovely bit of kit 8) standard BBC issue for the Film sound recording department in the past :wink:

ChrisB
I reject reality and substitute my own !!!!!!

Griffon
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Re: Audio recording of my CF's chain drive

Postby Griffon » Thu May 14, 2009 1:53 am

Thanks for replying, John and Chris! It had been over a month since I posted that recording, and I had almost given up hope anyone would respond.

Since I made that recording, I have mostly disassembled and then reassembled the chain drive. I did this mostly just to be sure there was nothing out of place or overly worn. When I opened the case, everything looked clean and in proper working order. The rubber pads that contact the chain to provide tension have wear grooves, but they are not deep and don't appear to be a problem. The only sign of something "not right" was some shallow grooves in the inside wall of the chain case near the motor sprocket, showing that the chains have at some point been rubbing against the wall (which I'm pretty sure is not supposed to happen).

The oil level was fine to begin with -- I checked that before I ever took the van out on the road. The oil was a little dirty, so I replaced it with fresh oil after I reassembled the drive case. I used straight 30 weight non-detergent oil, as it was on hand and seemed appropriate to the application. The shop manual I have says to use standard engine oil.

When I replaced the sprockets, I torqued the nuts as specified in the manual -- 80-90 ft-lbs (IIRC).

I have some photos I took of the chain case while it was disassembled, but they are not handy just at this moment. I will try to post them in the next couple days. I have been driving the CF and it still makes the same noises, so I guess my work didn't mess anything up badly.

VERY IMPORTANT QUESTION: How do I adjust the chain tensioner? I did not see any method of adjusting that component while I had the drive apart, unless "adjusting" means installing heavier springs. The shop manual I have does not discuss how to adjust the tensioner.

Chris - Yep, that's my Nagra IV-L! Wonderful machine, incomparable engineering. Would love to see an EV designed by Kudelski (the guy who designed the classic Nagra series).

- John

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Flying John
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Postby Flying John » Thu May 14, 2009 8:44 am

Hi John - sorry it took so long but I didnt get a notification that there had been subsequent posts and only came across it the other day when browsing around.


When I sold my CF the manuals went too , so I have not info on the chain tensioner adjustment. I am surprised there is not an adjustor cam just behind the "rubbing block" - on mine it was , what looked like, a piece of white PTFE.

I do have another motor and gearbox here but it is under loads of other stuff and would mean stripping it down to look, so I am not much help really.

The chain marks you have on the casing, doesnt sound right. Are you sure the chain hasnt stretched and is hitting the case under certian load conditions and that is what we hear on the recording.


JOhn

Griffon
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Re: Audio recording of my CF's chain drive

Postby Griffon » Fri May 15, 2009 2:36 pm

It's completely possible that the chains have stretched. I do have a another set of chains that came from my parts donor Griffon, but I did not make any comparison while I had the chain drive apart. I'd actually suspect that those chains are stretched too, as they have at least as many miles on them as the ones that are in use.

Take a look at the following photos (especially the last one).

(Sorry for the huge photos, but I wanted to be sure you could see everything in good detail!)

Here's a photo of the inside of the case with everything removed:

Image


Here's a close-up of where it looks like the chains are (or were at some point) hitting the case wall:

Image


Now everything's back together and ready for the cover to be replaced.

Image


- John

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Flying John
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Postby Flying John » Fri May 15, 2009 3:21 pm

Great pictures - if only everone did the same when they had something apart.

Without doubt it is stretched chain that has been forced out too far by the tensioner. Seems slightly different from mine and guess there is a single spring inside the tensioner and no adjustable part. So stretched chain, adjustor compensates and that brings it too close to the lower casing.

John

Griffon
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Re: Audio recording of my CF's chain drive

Postby Griffon » Sat May 23, 2009 1:07 am

Thanks, John. I'll have to start looking for a local place that can make up a new
set of chains for me.

Was chain stretch a common problem on these vans?

My chain tensioner actually does have two springs - one for each "rubbing block" assembly.

- John

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Flying John
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Postby Flying John » Sat May 23, 2009 7:06 am

I suppose the springs may have lost tension, and the chain be "wanging" around. If you move the chain by hand how close to the casing does it get ?. If it is close then I think it may have stretched. Its a shame you are so far away as you could of had my secondhand motor and gearbox - but its too far to ship such a weight.

I can ask around to see if anyone over here has an old chain from a gearbox you could have, but I am sure you could find a chain maker in the USA fairly cheaply


John

Griffon
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Re: Audio recording of my CF's chain drive

Postby Griffon » Thu Jul 02, 2009 2:15 am

Sorry it took me over a month to reply!

The Griffon was in the shop for three weeks waiting for some simple brake work (drum resurfacing) they just couldn't seem to get around to. But they finally got it done and brakes feel great now (and that right rear wheel doesn't tend to lock up anymore).

John - Since I sealed the chain drive case up just after I took those photos, I couldn't run out and check the "slackness" of the chain as you suggested in your last post. I do remember trying basically what you suggested before putting the cover back on, though. I certainly remember that I couldn't get the chains to come real close to touching the wall of the case. However, it's possible certain forces are set up when the chain is under high tension, and the chain is being thrown against the case wall in ways that wouldn't be obvious when observing the chain drive in a static condition.

I can still hear some chain "sing" once in a while, especially when driving up a hill. At least, I think it's the chain drive making that noise.

I have lots more I'd like to post about recent developments with the Griffon, but I'll start new threads for them in the next couple days.

Thanks!

- John


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