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Vintage Tape (Audio), Cassette, Wire and Magnetic Disc Recorders and Players Open-reel tape recorders, cassette recorders, 8-track players etc.

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Old 26th Mar 2020, 9:52 pm   #1
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Default Grundig TK14 etc. main drive belt

I know there are a few on here who, like me, have a few of the small Grundig reel to reel machines. Models this refers to are TK14, TK17, TK18, TK19, TK23 and TK27. The original flywheel drive belt is a round section of 2mm thickness. I have found that an O ring of suitable diameter is an excellent and much cheaper alternative to the genuine belts. I ordered 114mm diameter, but I feel that this is a touch on the tight side, so maybe 115 or 116 would be better. 114 will probably stretch over time.

There is no accomodation for any speed adjustment on these machines, but the motor pulley has quite a deep vee for the belt to sit in. If you find your machine is running a little slow, a 2.5mm cross-section belt sits slightly higher up in the pulley, so increasing the speed slightly.

Hope someone finds this useful,
Mark.
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Old 27th Mar 2020, 6:00 am   #2
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Default Re: Grundig TK14 etc. main drive belt

O-rings can be pre-stretched if they are a little tight. Just take the belt in hands and stretch it out a couple of times.

I too find O-rings excellent belt replacements many times, but the material is not as resilient (or 'stretchy') as real belts. In my opinion, it's fine if the belt is long, and the mechanics are up to it, but for shorter belts, they can be a little stiff. I sometimes worry that the stiffness will put an increased load on bearings, but on the other hand, many collector's machines are only run for short periods of time anyway.

I've also used them on many occasions for replacing friction tires on idlers.

A friend of mine even used them to refurbish a pinch roller - it was an early Tandberg type with flanges, so he put 4 or 5 O-rings of appropriate diameter beside each other between the flanges. According to him it worked fine; I've never tested it myself.
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Old 27th Mar 2020, 3:52 pm   #3
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Default Re: Grundig TK14 etc. main drive belt

In a previous job I used a wide range of O-rings (mainly for sealing vacuum chambers) and thought that in some instances that they could be suitable for R2R drive belts.
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Old 27th Mar 2020, 4:27 pm   #4
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Default Re: Grundig TK14 etc. main drive belt

I used O rings for sealing vacuum chambers as well. I often used long lengths of cord cut to length and super-glued together. I could never get that method to work for drive belts though, the splice always came apart.

Ricard - I agree that O rings are not as flexible as proper belts, this makes size selection more important. However, at the price it is worthwhile experimenting. I got 5 O rings for the above machines for just over 3. Time will tell how they hold up.

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Old 28th Mar 2020, 9:37 am   #5
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Default Re: Grundig TK14 etc. main drive belt

Yes, agreed.

Interesting Mark your comment about the splice always coming apart. I've had mostly good success, but I have a machine with a 2mm belt and I've had to glue it together several times, it seems to separate after some time like several months. I'm wondering if it has to do with the fact that it is rather thin, so the contact area is small relative to the belt tension. Or that I need to be more careful than usual when the glue is setting, for instance, put the belt in a vice or similar to keep it absolutely still while the glue hardens in order to get a maximum strength splice.
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Old 10th May 2020, 12:32 pm   #6
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Default Re: Grundig TK14 etc. main drive belt

Quote:
Originally Posted by ricard View Post
Yes, agreed.

for instance, put the belt in a vice or similar to keep it absolutely still while the glue hardens in order to get a maximum strength splice.

Am toying with a device for this purpose - really sophisticated, a slot sawed into a short length of hardwood. Plan is get a snug fit in the groove and ever so slightly over butt the glued end(s) so that when the join is pushed together there will be some tension in the right direction. Of course there are proper vulcanising machines, at a price and I missed out on an eBay one some time back
TT
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Old 11th May 2020, 9:03 pm   #7
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Default Re: Grundig TK14 etc. main drive belt

Interesting, let us know how you get on.

Didn't you used to be able to buy splicing kits from the likes of RS etc., or is my mind playing tricks on me?
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Old 12th May 2020, 12:08 pm   #8
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Default Re: Grundig TK14 etc. main drive belt

https://www.amazon.co.uk/480166-LOCT...9281670&sr=8-5
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Old 19th May 2020, 3:40 pm   #9
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Default Re: Grundig TK14 etc. main drive belt

Quote:
Originally Posted by 8 Tracker View Post
Interesting, let us know how you get on.

Didn't you used to be able to buy splicing kits from the likes of RS etc., or is my mind playing tricks on me?
You're right. This kit looks promising.(Amazon)

O Ring Splicing Kit - L&S Engineers Misc.

The URL link was too long for the page!
T
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Old 19th May 2020, 8:02 pm   #10
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Default Re: Grundig TK14 etc. main drive belt

The critical parts are a clean splice, which the kit takes care of and holding the two ends steady while the adhesive cures. Your block should do the job there, so you could be on to a winner.
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Old 19th May 2020, 8:48 pm   #11
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Default Re: Grundig TK14 etc. main drive belt

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The critical parts are a clean splice, which the kit takes care of and holding the two ends steady while the adhesive cures. Your block should do the job there, so you could be on to a winner.
--------------------------------------------------------------------------------------
The question is - have I enough confidence in my ability to saw a straight enough slot in a hardwood block? Answer: Probably not and the kit jig will be machine straight. Also there's the cord lengths and adhesive. The tape measure I can pass on to my child grandson. With all that I wouldn't save more than a couple of dinners in as compared with the home brew. And I can also do without the effort. My gnarled hands don't like saws any more. If I can overcome a slight aversion to handling Coved postal parcels I'll run with it
T
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