Can those simple design injectors do a good repair?

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Can those simple design injectors do a good repair?

Post by BrightFastWSR »

I plan to have a try in windshield repair business.

As I am uncertain of how the local market is and there has been other chain stores offer such service with low price, I'd like to minimize the investment to start with first.

Till now what I found the simplest design of injectors are screw type injectors with a small inner o ring attached on the far end of the plunger and an o ring end seal outside. I have several questions for a professional answer possible:

1. Can such simple design injector do a good windshield repair on all type of breaks such as bullseye, star breaks, combination and long cracks after some DVD trainning and constant practice?

2. I have seen many of such design injectors made of different materials, the cheapest are made of plastics, and other materials I have ever seen are alluminized alloy, high speed steel, brass and stainless steel. I know stainless steel injectors should be best, what I want to know if the injector made of other materials e.g. plastics, alluminized alloy, high speed steel or brass also works? Will the resin corrode these materials or will these materials contaminate the resin?

3. The other difference of this simplest design is the end seal design. Some injectors use the long boot end seal design and other just use another O ring as end seal. Do you think which is better design? It seems the long boot design end seal needs to be replaced more frequently than O ring design end seal , is that correct?

I'd like to know the pros and cons of this design injectors to make a repair and I appreciate very much if anyone can give some advices. Thank you.
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Brent Deines
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Re: Can those simple design injectors do a good repair?

Post by Brent Deines »

Some on this forum will disagree with me, but I'll give you my opinion and let them give theirs.

We still sell a lot of simple screw type injectors with great success. Novus and many other successful companies also still sell a simple screw type design. Although there has been a shift in much of the industry to vacuum first systems, there is no denying that an injector does not need to be complicated to work well. The amount of air in a break is miniscule so it does not take a lot of pressure and even less vacuum to properly fill a break. Screw type injectors are still very efficient for this purpose.

When you remove air from a break you need a place for that air to go. With one or two notable exceptions, injectors that use o-rings on the end of the plunger pull air from the break but it is then trapped above the resin, so now instead of using the plunger to force auto glass resin into the break you are using air. Use enough pressure and you will introduce air back into the break...not good. It's a very simple principal that anyone who has worked with automobile braking systems or other hydraulic applications understands, but somehow seems to be often ignored in the auto windshield repair industry.

As far as the seal between the glass and the injector, a good o-ring works just fine, but again, many systems that use an o-ring for that purpose also use one at the end of the plunger which does not allow for air to be completely evacuated from the cylinder, and are therefore inefficient hydraulic systems. For those systems that utilize a custom molded end seal to create pressure and vacuum, the length, wall thickness and design make a big difference in how efficiently they apply pressure and remove air. You need to completely remove the plunger from the end seal to allow air to escape and keep it completely full of resin for peak hydraulic efficiency. If you don't you still have air in your system. Too long of a seal and you will have to use a lot of resin, too short and you will not have enough pressure to fill the break. Too thin of a wall or if the piston is not sized properly for the cylinder and you will lose friction and allow resin to leak back into the cylinder. Too tight and you wear out end seals prematurely.

The material that the end seal is made from is extremely important. In our testing we soak end seals in alcohol and resin for extended periods of time. It's shocking to see how many end seals fail this test. Some shrink in alcohol an get hard as a rock while others swell and soften in resin. Still others turn the resin yellow. Just using a rubber o-ring or chunk of rubber hose from your local auto parts store just doesn't cut it, yet we see these materials being used all the time, even by some of the major suppliers.

Do plastic, aluminum and brass injectors work? The short answer is yes! However, plastic wears out making it difficult to maintain tight tolerances. Plastic also shrinks during the cooling stage of the molding process, again, making it impossible to maintain tight tolerances. Aluminum is inexpensive and very easy to machine so it is very popular but it also wears out, leaving little fragments of aluminum in your repairs. You'll notice that aluminum turns your hands and everything else it touches black. It also leaves some black in the resin you inject into the glass. Anodized aluminum is a hard coat put over the aluminum for better wear, but it too wears off, leaving fragments of the anodize material and aluminum in your repairs. Brass is also very easy to machine and therefore inexpensive to machine, but it too is soft and wears, leaving brass fragments in your repair. Brass also reacts negatively to many chemicals. I can't remember the last time I saw a brass injector, although sometimes technicians think that the gold anodized injectors are brass. How do I know all this? Delta Kits started out selling plastic injectors, graduated to aluminum, then anodized aluminum, and finally bit the bullet and went to a high grade of stainless steel for all of our injectors. It's probably been 15 years or more ago that we made the switch to stainless steel and have never looked back. Brass is the only thing we did not ever sell, although we did do plenty of testing before rejecting the idea.

Whether you buy from us or someone else I hope this at least helps answer some of your questions about screw type injectors.
Brent Deines
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Re: Can those simple design injectors do a good repair?

Post by autocosmetics »

Excellent informative reply Brent! All I can add to that is I've probably bought most of the equipment out there (I still have a big box of used equipment!), and when I was first getting started I didn't seem to get the hang of windshield repair with any injector I bought. But now I can say that I could pull out any injector and do a good repair. It really wasn't the equipment, it was my inexperience. Learning to be good took lots of practice. The plastic screw type injectors do seem to take me a little longer, but I still use one from time to time.

No matter what equipment you choose, try to make it for training somewhere. It will really make a difference in the learning curve, I know it did for me.

Jim
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Re: Can those simple design injectors do a good repair?

Post by BGW »

Wow thanks Brent! That answered alot of my questions as well about the different materials the injectors are made of. Soon I will be purchasing a kit from Delta and I'm sure will be very pleased!
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Re: Can those simple design injectors do a good repair?

Post by BrightFastWSR »

Thank you very much, Brent. I think everyone in this forum who will be successful in the WR business in future will has Delta products later due to your helpfulness,open-mindedness and professional knowledge concentrating on WR so many years.
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Re: Can those simple design injectors do a good repair?

Post by BrightFastWSR »

Thank you very much for your answer, Jim. About the learn curve, I attach a pictur here, Image, do you mean more practice will make the repair results better and less time in doing the windshield repair no matter what kind of injectors to start ? Thank you.
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Re: Can those simple design injectors do a good repair?

Post by screenman »

I used plastic injectors for about 19 years I now use the Delta one, I like the way it works and looks. I certainly could do quality repairs with the plastic one, but for sure I am sticking with this nice shiny one I have now.

The one thing I know is that the correct practise should make you better at the job, the incorrect practise is extremely unlikely to make you good though.

Speculate to accumulate, buy the best you can training wise and tools wise, invest time and effort along with plenty of determination and with a little luck which you can make yourself things hopefully will happen.

I thank Delta for giving this forum to the trade and I am sure plenty of others do the same, there is a wealth of information on here.
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Re: Can those simple design injectors do a good repair?

Post by autocosmetics »

BrightFastWSR,

I can only speak of my own experiences in regard to a learning curve. I bought my first windshield repair kit back in the '90s and practiced on an old windshield that I set on my dining room table on a homemade wooden stand. I have to laugh looking back because I was making the most hideous damages on the glass and then getting frustrated because I couldn't repair them. After coming to the conclusion that windshield repair was a scam, the kit went in my closet for a few years and then I sold it for a fraction of what I paid for it.

Fast forward several years and seeing stone chips repaired on my own vehicles, I was kicking myself for not sticking with it. Had I taken the time to go for training, I really think I could have discovered any mistakes I was making and learned tips that would have helped me out. Regardless of whether you go for training or just use a training video, and no matter what equipment you decide to use, the more repairs you do the more confident you will get and the better and quicker your repairs will be. I remember a time when I couldn't figure out if all the legs of a star break were filled, or if there was water in the break, or what to do if the leg of a star break started to run. I'd get really nervous, but now no matter what I'm faced with I know I can handle it.

Again, this is just my own experience with windshield repair. I also have been doing vinyl and leather repair since the '70s and again it was just me learning it on my own. I bought all kinds of different supplies, tried out everything and took what worked best for me in regard to equipment, materials and procedures. I know I could teach someone in a very short time what took me many, many years to perfect. That's why I tell you that in my opinion I feel there's no substitute for training from those that have all the knowledge and experience.

All the best to you,

Jim
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Re: Can those simple design injectors do a good repair?

Post by BrightFastWSR »

Jim,

Thank you so much to share your personal experience in windshied repair field, which is very helpful to me to face possible difficulties in windshield repair in future and stick to it. Till now I have viewed almost all repair videos on youtube.com , and I read some "wise crack" articles written by Brent. I can not get professional hand-on trainning here and my trainer is just my computer. lol... However, on the other side of the computer, I have you, Brent and all other helpful friends in this forum, I think I can do a good job in future.

Thank you very much and all the best to you,

Bill
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Re: Can those simple design injectors do a good repair?

Post by screenman »

If you could post some picture if anything goes wrong then that would be a big help.

Do not forget to make them wet. Also some done outside is a big help in training.
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