TD Carb body replacement
10-12-2006, 11:58 AM
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RE: TD Carb body replacement
Prop,
If your talking about the plastic piece it's pretty easy. Remove backplate, unscrew cylinder/piston, tap out crankshaft like you would with any Cox engine, remove front collar. I believe the Cox 1/2a wrench has a slot for it. Take off old plastic carb piece. Sometimes it takes alittle work to get it unseated but you'll get it.
Later,
Tim
If your talking about the plastic piece it's pretty easy. Remove backplate, unscrew cylinder/piston, tap out crankshaft like you would with any Cox engine, remove front collar. I believe the Cox 1/2a wrench has a slot for it. Take off old plastic carb piece. Sometimes it takes alittle work to get it unseated but you'll get it.
Later,
Tim
10-12-2006, 01:06 PM
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RE: TD Carb body replacement
ORIGINAL: Tim Wiltse-RCU
Prop,
If your talking about the plastic piece it's pretty easy. Remove backplate, unscrew cylinder/piston, tap out crankshaft like you would with any Cox engine, remove front collar. I believe the Cox 1/2a wrench has a slot for it. Take off old plastic carb piece. Sometimes it takes alittle work to get it unseated but you'll get it.
Later,
Tim
Prop,
If your talking about the plastic piece it's pretty easy. Remove backplate, unscrew cylinder/piston, tap out crankshaft like you would with any Cox engine, remove front collar. I believe the Cox 1/2a wrench has a slot for it. Take off old plastic carb piece. Sometimes it takes alittle work to get it unseated but you'll get it.
Later,
Tim
Yup, there is a slot for the front collar on the Cox wrench.
I repaired my TD .049 carb body quickly and easily - it had split down the side of the threaded part into which the venturi screws. I tested it with a bit of solvnet and found out it is a high surface energy plastic, probably ABS, so gluing is possible. Here's what I did:
- cleaned it with alcohol to remove oil and crud
- lightly lubed the venturi threads, then screwed it in to act as a form
- bound the carb body tightly with cotton thread to haul it back into shape
- saturated the thread with thin plastic CA, then quickly unscrewed the venturi
- overcoated the CA part with epoxy to protect it from raw fuel (nitromethane is an excellent solvent for cured CA)
Works like a champ. If anyone cares I'll take a picture of the repair tonight and post it.
MJD
10-12-2006, 08:54 PM
#4
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RE: TD Carb body replacement
Nicely thought out repair. Thanks for sharing.
Did you think about using a solvent bonder like Tenax-7R instead of the CA? It works great on ABS and other hard plastics and wouldn't be susceptible to debonding when hit with nitromethane.
Did you think about using a solvent bonder like Tenax-7R instead of the CA? It works great on ABS and other hard plastics and wouldn't be susceptible to debonding when hit with nitromethane.
10-12-2006, 08:57 PM
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RE: TD Carb body replacement
ORIGINAL: lildiesel
Nicely thought out repair. Thanks for sharing.
Did you think about using a solvent bonder like Tenax-7R instead of the CA? It works great on ABS and other hard plastics and wouldn't be susceptible to debonding when hit with nitromethane.
Nicely thought out repair. Thanks for sharing.
Did you think about using a solvent bonder like Tenax-7R instead of the CA? It works great on ABS and other hard plastics and wouldn't be susceptible to debonding when hit with nitromethane.
10-13-2006, 12:31 AM
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RE: TD Carb body replacement
I’ve not seen Tenax-7R, but is anyone familiar with Ambroid Proweld? Sounds like it may be a similar product. It is the only solvent on my shelf that will weld Plexiglas (Lucite). Don’t know how it would stand up to nitro tho.
I also have some TD’s with cracks in the plastic carb adapter that need repair.
Al
I also have some TD’s with cracks in the plastic carb adapter that need repair.
Al
ORIGINAL: lildiesel
Nicely thought out repair. Thanks for sharing.
Did you think about using a solvent bonder like Tenax-7R instead of the CA? It works great on ABS and other hard plastics and wouldn't be susceptible to debonding when hit with nitromethane.
Nicely thought out repair. Thanks for sharing.
Did you think about using a solvent bonder like Tenax-7R instead of the CA? It works great on ABS and other hard plastics and wouldn't be susceptible to debonding when hit with nitromethane.
10-13-2006, 05:41 AM
#7
RE: TD Carb body replacement
Well, I tried just unscrewing the retaining collar but it wouldn't push the drive washer off. Followed Tim's instructions and swapped out the old one for a new, well, used but good, carb body. Added a KK fine thread needle valve assembly and she now runs great! In my backyard that is, once I get her to the field she'l probably turn back into the finicky little devil I remember. 
Thanks, Prop
Thanks, Prop
10-13-2006, 06:57 AM
#8
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RE: TD Carb body replacement
ORIGINAL: Big Al-RCU
I’ve not seen Tenax-7R, but is anyone familiar with Ambroid Proweld? Sounds like it may be a similar product. It is the only solvent on my shelf that will weld Plexiglas (Lucite). Don’t know how it would stand up to nitro tho.
I also have some TD’s with cracks in the plastic carb adapter that need repair.
Al
I’ve not seen Tenax-7R, but is anyone familiar with Ambroid Proweld? Sounds like it may be a similar product. It is the only solvent on my shelf that will weld Plexiglas (Lucite). Don’t know how it would stand up to nitro tho.
I also have some TD’s with cracks in the plastic carb adapter that need repair.
Al
10-13-2006, 07:07 AM
#9
RE: TD Carb body replacement
I guess I had better try repairing my old carb body before tossing it in the trash. http://www2.towerhobbies.com/cgi-bin...&I=LXHU34&P=WR I wonder if it's available locally.
10-13-2006, 08:43 AM
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RE: TD Carb body replacement
- cleaned it with alcohol to remove oil and crud
- lightly lubed the venturi threads, then screwed it in to act as a form
- bound the carb body tightly with cotton thread to haul it back into shape
- saturated the thread with thin plastic CA, then quickly unscrewed the venturi
- overcoated the CA part with epoxy to protect it from raw fuel (nitromethane is an excellent solvent for cured CA)
- lightly lubed the venturi threads, then screwed it in to act as a form
- bound the carb body tightly with cotton thread to haul it back into shape
- saturated the thread with thin plastic CA, then quickly unscrewed the venturi
- overcoated the CA part with epoxy to protect it from raw fuel (nitromethane is an excellent solvent for cured CA)
Luke.
10-13-2006, 08:49 AM
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RE: TD Carb body replacement
If the body is indeed ABS, there is nothing fundamentally wrong with bonding it with plain old ABS cement, which is merely ABS dissolved in a blend of solvents. An alternative that works on ABS, PVC and CPVC, is CPVC cement. Thorough cleaning with alcohol is still a good idea first. I am totally familiar with solvent bonding techniques, but since I wanted to ensure structural integrity I chose to overwind the body. The particular CA I use, which I use industrially in my day gig, is extremely aggressive with ABS, and in fact if you yield the bondline will tear the substrate when the bond is done correctly. The repair I did is holding up like a champ and due to the overcoating does not appear to have degraded one bit.
Another possible hybrid of the two techniques would be to dip the cord in solvent cement then quickly overwrap the body, after first bonding it together as is. Or if if flashes off too quickly, Possibly one layer of overwrap, a brush with cememnt, and maybe one more overwrap and cement brushing. Whatever, I think all the above will work just fine.
Two-part methacrylic adhesives such as (darn, is it Devcon or Lepages?) Plastic Welder are a natural for the job. I didn't have any at home when I fixed it. These methacrylic adhesives stick like troll snot to the plastics mentioned above, as well as pretty well to clean aluminum. We use them for a number of odd substrate bonding jobs here. I have bonded aluminum to ABS with them, then tested the bondlines to failure - flecks of each material were torn from the surface - that's about as strong as you'll ever need!
The most important lesson for me, is that I will refrain from overtightening the venturi in the future...
MJD
Another possible hybrid of the two techniques would be to dip the cord in solvent cement then quickly overwrap the body, after first bonding it together as is. Or if if flashes off too quickly, Possibly one layer of overwrap, a brush with cememnt, and maybe one more overwrap and cement brushing. Whatever, I think all the above will work just fine.
Two-part methacrylic adhesives such as (darn, is it Devcon or Lepages?) Plastic Welder are a natural for the job. I didn't have any at home when I fixed it. These methacrylic adhesives stick like troll snot to the plastics mentioned above, as well as pretty well to clean aluminum. We use them for a number of odd substrate bonding jobs here. I have bonded aluminum to ABS with them, then tested the bondlines to failure - flecks of each material were torn from the surface - that's about as strong as you'll ever need!
The most important lesson for me, is that I will refrain from overtightening the venturi in the future...
MJD
